Effect of Bagasse Fiber on the Flexural Properties of Biodegradable Composites

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玄武岩纤维掺量对混凝土性能的影响及增强机理

试验与应用玄武岩纤维掺量对混凝土性能的影响及増强机理Experimental Investigation on Basalt Fiber of the Basic Properties of Concrete and Strengthening Mechanism徐珍珍(陕西铁路工程职业学院，渭南714000)摘要：以玄武岩纤维体积掺量（0、0.1%、0.2%、0.3%)为试验参数，开展玄武岩纤维掺量对混凝土基本性能的研究工作。

试验结果表明：玄武岩纤维满足制备纤维混凝土的基本要求；抗压性能随掺量的增加呈现先增加后减小的趋势，抗折性能随掺量的增加而增强，建议玄武岩纤维体积掺量范围为0.1%~0.2% ;玄武岩纤维表面被水泥水化物包裹并且黏结良好，可抑制荷载作用时裂缝的扩展，提高混凝土的韧性。

关键词：玄武岩纤维；掺量；混凝土性能；增强机理中图分类号：TQ343+.4 ;U214.1+8 文献标识码：A文章编号：1005-8249 (2019 ) 06-0023-04XU Zhenzhen(Shaanxi Railway Institute,Weinan714000, China)Abstract: Taking the volume rate of basalt fiber (0、0.1%、0.2%、0.3%) as test parameters, the basic properties of concrete was carried out. The results shows that basalt fibers meet the basic requirements of preparing fiber concrete The compressive resistance of basalt concrete increases and decreases with the increase of fiber content, and the flexural resistance increases with the increase of fiber content. We suggest that the volume of fiber content should be in the extent of 0.1%~0.2%; It was observed that it is well-bonded between cement hydrates and the basalt fibers .Basalt fibers not only increases with the flexural resistance of concrete and prolongs the development time of initial crack to crack in m atrix, but also inhibits the expansion of its cracks.Keywords: basalt fiber; dosage; concrete properties; strengthening mechanismo引言随着国内基础设施向地下、生态节能、高空、高耐久性等方向的建设和发展，工程建设对混凝土提出更多的要求。

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OLYMPUS FIBERSCOPESStandard RangeOlympus Fiberscopes - Standard range - 6, 8 and 11mm diameter Flexible fiberscopes allow remote visual inspection to be carried out in areas where the route to the area of interest includes negotiating a series of bends or where the length of instrument required is outside the limits of a rigid borescope.The construction of an Olympus fiberscope is a specialized process, requiring a combination of advanced optical and mechanical technologies, resulting in a finished product with many highperformance design features:Interchangeable optical tip adaptors . The focus of the optical system is fixed, however, each inspection has different requirements with regard to depth of field and direction of view. For this reason, all standard model fiberscopes have interchangeable optical tip adaptors to provideversatility and are available in direct or side viewing configuration - just select the tip adaptor most suitable for the application. Separately, a diopter focus compensates for the individual s eyesight.Image size. The Olympus image size is larger than most other fiberscopes. Due to the optical quality, the image of an Olympus fiberscope can be magnifed and maintain a high resolution image.Tapered Flexibility. This feature provides graduated flexibility along the length of the insertion tube, making the insertion tube more flexible towards the distal end.Four layer insertion tube. The construction of the insertion tube (the part of the instrument inserted into the application area) is especially important to ensure reliability and durability, but without compromising flexibility. Olympus have excelled in this area, creating a design of four individual layers which together protect the internal components and provide fluid resistance.Four-way angulation. All models feature four-way angulation of the distal end, which aids insertion and maneuverability and helps to steer the tip towards the inspection area.The Series 5 range of industrial fiberscopes is available in a variety of diameters and workinglengths. All instruments feature an eyepiece which allows compatibility with a range of CCTV and Photographic adaptors so that the image normally seen through the eyepiece can be recorded for future reference and reporting./Olympus-IF2D5-12-Borescope.aspxTo buy, sell, rent or trade-in this product please click on the link below:Temperature:Insertion tube (in air): -10 to 80°C (14 to 176°F)Complete instrument (in air): -10 to 50°C (14 to 122°F)Pressure:Insertion tube at 10 to 30°C: 1 to 1.3 bar absoluteFluid resistance:The insertion tube can be immersed for short periods, and control body wiped with, the following chemicals: Water, 5% salt water, machine oil and light oilSmall DiameterOlympus Fiberscopes - Small diameter - 0.6, 2.4 and 4.1mm diameterIn some applications, the entry port size to the area of interest can be restricted and inserting a scope can be extremely difficult. This will often necessitate using an instrument of smaller diameter than conventional models.The Olympus range of small diameter fiberscopes is designed for these applications and are available in diameters 0.6, 2.4 and 4.1mm (0.02, 0.09 and 0.16") and lengths of up to 1.5m (4.9 ). All instruments feature a high resolution coherent fiberoptic bundle for image transmission and a separate channel of non-coherent fibers for illuminating the inspection area. To aid insertion and maneuverability once inside the entry port, all instruments feature a strong, reliable insertion tube construction and in the case of the 2.4mm and 4.1mm, two-way angulation helps steer the tip towards the target area. Additionally, 4.1mm diameter models have the Olympus Tapered Flexibility insertion tube design, which means that the insertion tube becomes gradually more flexible towards the distal end - a feature not normally associated with small diameter instruments. All instruments have ocular focus to ensure that the individual operator s eyesight is accommodated and can be attached to CCTV and photographic equipment to allow the images to be permanently recorded. To illuminate the inspection area, any one of the Olympus light sources can be used.The tables below show the models available and their specifications:Model Name Diameter Length TaperedFlexibilityAngulationDirection ofViewField ofViewDepth of Field Eyepiece styleIF6PD4-60.64mm(0.02")490mm(19.3")No No Direct58°1-50mm (0.03-2.0")32mmIF6PD4-110.64mm(0.02")990mm(39.0")No No Direct58°1-50mm (0.03-2.0")32mmIF2D5-6 2.4mm(0.09")600mm(23.6")No120° Up/Down Direct75°2-50mm (0.08-2.0")32mmIF2D5-12 2.4mm(0.09")1170mm(46.06")No120° Up/Down Direct75°2-50mm (0.08-2.0")32mmIF4D5-7 4.1mm(0.16")700mm(27.6")Yes120° Up/Down Direct65°5-60mm (0.2-2.4")OES StyleIF4D5-15 4.1mm(0.16")1500mm(59.0")Yes120° Up/Down Direct65°5-60mm (0.2-2.4")OES StyleIF4S5-7 4.1mm(0.16")700mm(27.6")Yes120° Up/Down Side (90°)60°4-40mm (0.16-1.6")OES StyleIF4S5-15 4.1mm(0.16")1500mm(59.0")Yes120° Up/Down Side (90°)60°4-40mm (0.16-1.6")OES StyleEnvironmental Specification:IF6PD4IF2D5IF4D5 / IF4S5 Temperature:Insertion tube (in air) Complete Instrument (in air)0 to 40°C(32 to 104°F)10 to 30°C(32 to 86°F)-10 to 80°C(14 to 176°F)-10 to 50°C(14 to 122°F)-10 to 80°C(14 to 176°F)-10 to 50°C(14 to 122°F)Pressure:Insertion tube at10-30°C1 to 1.3 bar absolute 1 to 1.3 bar absolute 1 to 1.3 bar absolute Fluid Resistance:The insertion tube can be immersed for short periods, and control body wiped with:Water Water Water5% salt watermachine oillight oilSpecial Feature FiberscopesThere are some RVI applications that cannot be satisfied by a standardmodel fiberscope. Olympus has always been at the forefront ofapplication solutions, and when a situation arises where a standardinstrument will not provide the desired results, then Olympus hasresponded with advice on optimal instrument use in that application.This occasionally results in the introduction of a special instrumentdesigned to meet that specific requirement - these are therefore knownas special feature fiberscopes. This is not to say, however, that theycannot be used in other applications. The information below describeseach model, together with its design application, but the specificationmay well suit a particular inspection you need to undertake.IF5D4X1-14:At 5.0mm (0.19") diameter and 1200mm (47") working length, thisinstrument was initially developed and approved for the Pratt &Whitney PT6 engine, but has since become used for the inspection ofmany small engines and fine diameter pipework. It features two-wayangulation, and interchangeable optical tip adaptors, allowing direct orside view, both supplied as standard with the instrument.IF7D3X3-26 / IF7D3X3-32:This 7.3mm (0.29") diameter instrument has been approved for use onthe F100 and JT-9D aircraft engines and features an internal channelfor introducing a working tool or guide hook into the inspection areato aid navigation around the engine. It features four-way angulation(130° up, down, left and right) and the optical system is set to a 66°field of view, fixed focus (depth of field 8mm to infinity).IF8D3X2-23:The JT-8D engine inspection can be particularly difficult and is mosteffectively undertaken using an instrument in conjunction with a guidetube. TheIF8D3X2-23 fiberscope has been designed for this inspection and has been specified with an 80° field of view and a unique angulation range - 185°up, 105° down, left and right. This is then used with the MD-999 guide tube to achieve angulation in eight different directions.Visit the Guide Tube section of the product information to see details of theMD-999.IF8D4X2-10:This instrument has been purpose-designed for use within the automotive industry, with an 8.5mm (0.33") diameter and 770mm (30") working length. It is a general diagnostic tool for trouble-shooting as well as analysis of specific problems. Typical areas of use include intake and exhaust valves, cylinders, transmission systems and areas within the chassis. Unlike other fiberscopes of this diameter, the IF8D4X2-10 has a 32mm diameter eyepiece, which allows it to be connected to the standard range of accessories associated with rigid borescopes.IF13D3-60:At 6050mm (19 ) length, the IF13D3-60 is the longest industrial fiberscope in production today. It is specifically designed for the visual inspection of plant such as pipes, boilers and heat exchangers, where the area of interest is some distance from the access point. It has four-way angulation of the distal end and is compatible with a wide range of 11mm diameter interchangeable optical tipadaptors, providing the user with a variety of fields of view and depth of field characteristics.Visit the Ultra-Long Videoscopes section for information on alternative long instruments.UV (Ultra Violet) FiberscopeGlass fibers used in borescopes and standard specification fiberscopes attenuate UV light and can only therefore be used to view the fluorescing images, not to transmit UV illumination. In order to transmit ultra-violet illumination and view the images with one instrument, a special feature fiberscope is required.The IF11D4-20UV fiberscope is available with or without an internal channel and features a quartz fiber bundle for effective ultra-violet illumination. The 11.3mm (0.44") diameter instrument is available in two lengths - 2.0m or 3.0m (6.6 or 9.8 ) and ,where specified, the internal channel can be used to introduce the dye and processing fluid necessary in this application.Please note that the UV fiberscope is only available as a special production item and is therefore subject to a longer delivery lead time.Olympus offers a special high power UV light source for use with this fiberscope for dye penetrant inspections.。

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/Journal of Reinforced Plastics and Composites/content/30/19/1621The online version of this article can be found at:DOI: 10.1177/07316844114268102011 30: 1621 originally published online 7 November 2011Journal of Reinforced Plastics and Composites N. Venkateshwaran, A. ElayaPerumal and M. S. JagatheeshwaranEffect of fiber length and fiber content on mechanical properties of banana fiber/epoxy compositePublished by: can be found at:Journal of Reinforced Plastics and Composites Additional services and information for/cgi/alerts Email Alerts:/subscriptions Subscriptions: /journalsReprints.nav Reprints:/journalsPermissions.nav Permissions:/content/30/19/1621.refs.html Citations:What is This?- Nov 7, 2011OnlineFirst Version of Record- Dec 16, 2011Version of Record >>ArticleEffect of fiber length and fiber contenton mechanical properties of banana fiber/epoxy compositeN.Venkateshwaran,A.ElayaPerumal and M.S.JagatheeshwaranAbstractThe main factors that influence the properties of composite are fiber length and content.Hence the prediction of optimum fiber length and content becomes important,so that composite can be prepared with best mechanical prop-erties.Experiments are carried out as per ASTM standards to find the mechanical properties namely,tensile strength and modulus,flexural strength and modulus,and impact strength.In addition to mechanical properties,water absorption capacity of the composite is also studied.Further,fractured surface of the specimen are subjected to morphological study using scanning electron microscope.The investigation revealed the suitability of banana fiber as an effective reinforce-ment in epoxy matrix.Keywordspolymer composites,banana fiber,mechanical properties,scanning electron microscopeIntroductionNowadays,polymers are used everywhere in the day-to-day life.Plastics found its way when the need for low weight high strength material became important for various applications.The research in theﬁeld of poly-mer and polymer-based components has gained wide-spread recognition owing to its property;however,its bio-degradability is still a matter of concern.Further, glassﬁber reinforced polymers(GFRP)have become appealing substitutes for aluminum,concrete,and steel due to its high strength-to-weight ratio,ease of handling,and for being corrosion-free.Moreover, they can also be engineered to get the desired proper-ties.1Since large-scale production and fabrication of glassﬁber causes environmental problems and also health hazards,a suitable alternate which is environ-mental friendly is the need of the hour.Naturalﬁbers that are low cost,lightweight and environmental friendly provide an excellent alternative to glassﬁber. Joshi et al.2reviewed the life cycle assessment of natural ﬁber and glassﬁber composite and found that natural ﬁbers are environmentally superior to glassﬁber,and also reduces the polymer content as reinforcement. Schmidt and Beyer,Wotzel et al.,and Corbiere et al.carried out some important works using the natural ﬁbers as reinforcement in polymer matrix for use in automobile parts.Schmit and Beyer3have replaced the glassﬁber polypropylene(PP)with hemp-PP com-posite for auto-insulation application.Wotzel et al.4 have used hemp-epoxy to replace glassﬁber acryloni-trile butadien–styrene(ABS)for usage in auto-side panel.Similarly,Corbiere et al.5replaced glassﬁber PP with Curaua PP for transporting pallet.All these studies revealed that the naturalﬁber based polymer composite has successfully replaced the glassﬁber. Pothan et al.6studied the eﬀect ofﬁber length and con-tent on the mechanical properties of the short banana/ polyester composite.Study shows that30–40mmﬁber length and40%ﬁber loading provides better mechan-ical properties.Idicula et al.7investigated the mechan-ical performance of banana/sisal hybrid composite and Department of Mechanical Engineering,Anna University,Chennai,India.Corresponding author:N.Venkateshwaran,Department of Mechanical Engineering,Anna University,Chennai,IndiaEmail:venkatcad@Journal of Reinforced Plasticsand Composites30(19)1621–1627!The Author(s)2011Reprints and permissions:/journalsPermissions.navDOI:10.1177/0731684411426810the positive hybrid eﬀect for tensile strength was found to be in the ratio of4:1(banana:sisal). Further,the tensile strength of the composite is better when bananaﬁber is used as skin and sisal as core material.Visco-elastic property of the banana/ sisal(1:1ratio)hybrid composite was studied by Idicula et al.8The study shows that sisal/polyester composite has maximum damping behavior and high-est impact strength as compared to banana/polyester and hybrid composite.Sapuan et al.9prepared the composite by reinforcing woven bananaﬁbers with epoxy matrix.Tensile test result showed that the woven kind of reinforcement has better strength and the same was conﬁrmed using Anova technique also. Venkateshwaran and ElayaPerumal10reviewed the various work in theﬁeld of bananaﬁber reinforced with polymer matrix composite with reference to phys-ical properties,structure,and application. Venkateshwaran et al.11studied the eﬀect of hybridi-zation on mechanical and water absorption properties. Investigation revealed that the addition of sisal in bananaﬁber composite upto50%increases the mechanical properties.Sapuan et al.12designed and fabricated the household telephone stand using woven banana fabric and epoxy as resin.Zainudin et al.13studied the thermal stability of banana pseudo-stem(BPS)ﬁlled unplastisized polyvinyl chlo-ride(UPVC)composites using thermo-gravimetric analysis.The study revealed that the incorporation of bananaﬁller decreases the thermal stability of the composite.Zainudin et al.14investigated the eﬀect of bananaﬁller content in the UPVC matrix.The inser-tion ofﬁller increases the modulus of the composite and not the tensile andﬂexural strength.Zainudin et al.15studied the eﬀect of temperature on storage modulus and damping behavior of bananaﬁber rein-forced with UPVC.Uma Devi et al.16studied the mechanical properties of pineapple leafﬁber rein-forced with polyester composite.Study found that optimum mechanical properties are achieved at 30mmﬁber length and30%ﬁber content.Dabade et al.17investigated the eﬀect ofﬁber length and weight ratio on tensile properties of sun hemp and palmyra/polyester composite.The optimumﬁber length and weight ratio were30mm and around 55%,respectively.From the above literatures,it is evident that the ﬁber length and content are the important factors that aﬀect properties of the composite.Hence in this work,the eﬀect ofﬁber length and weight percentage on the mechanical and water absorption properties of the bananaﬁber epoxy composite is investigated. Further,the fractured surface of the composite are subjected to fractography study to evaluate the frac-ture mechanism.ExperimentalFabrication of compositeA molding box made of well-seasoned teak wood of dimensions300Â300Â3mm3is used to make a com-posite specimen.The top,bottom surfaces of the mold and the walls are coated with remover and kept for drying.Fibers of diﬀerent length(5,10,15,and 20mm)and weight percentage(8,12,16,and20)are used along with Epoxy(LY556)and Hardener (HY951)for the preparation of composite.Testing standardsThe tensile strength of the composite was determined using Tinnus Olsen Universal Testing Machine (UTM)as per ASTM D638standard.The test speed was maintained at5mm/min.In this case,ﬁve specimens were tested with variedﬁber length andﬁber weight ratio.The average value of tensile load at breaking point was calculated.Theﬂexural strength was determined using the above-mentioned UTM as per ASTM D790procedure.The test speed was maintained between1.3and1.5mm/min. In this case,ﬁve samples were tested and the average ﬂexural strength was reported.The impact strength of the composite specimen was determined using an Izod impact tester according to ASTM D256 Standards.In this case,ﬁve specimens were tested to obtain the average value.Figures1to5show the eﬀect ofﬁber length and weight content on ten-sile,ﬂexural,and impact properties.Water absorp-tion behavior of banana/epoxy composites in water at room temperature was studied as per ASTM D570to study the kinetics of water absorption. The samples were taken out periodically andFigure1.Effect of fiber length and weight percentage on tensile strength.1622Journal of Reinforced Plastics and Composites30(19)weighed immediately,after wiping out the water from the surface of the sample and using a precise 4-digit balance to ﬁnd out the content of water absorbed.All the samples were dried in an oven until constant weight was reached before immersing again in the water.The percentage of moisture absorption was plotted against time (hours)and are shown in Figures 6–13.Scanning electron microscopeThe fractured surfaces of the specimens were exam-ined directly by scanning electron microscope Hitachi-S3400N.The fractured portions of the sam-ples were cut and gold coated over the surface uni-formly for examination.The accelerating voltage used in this work was 10kV.Figures 14to 17show the fractured surface characteristics of the compositespecimen.Figure 6.Effect of moisture on fiber content;Fiber length –5mm.Figure 3.Effect of fiber length and weight percentage on flexural strength.Figure 2.Effect of fiber length and weight percentage on tensilemodulus.Figure 4.Effect of fiber length and weight percentage on flexuralmodulus.Figure 5.Effect of fiber length and weight percentage on impact strength.Venkateshwaran et al.1623Figure 12.Effect of moisture on fiber length;Fiber wt%–16.Figure 7.Effect of moisture on fiber content;Fiber length –10mm.Figure 11.Effect of moisture on fiber length;Fiber wt%–12.Figure 10.Effect of moisture on fiber length;Fiber wt%–8.Figure 8.Effect of moisture on fiber content;Fiber length –15mm.Figure 9.Effect of moisture on fiber content;Fiber length –20mm.1624Journal of Reinforced Plastics and Composites 30(19)Results and discussion Mechanical propertiesFor the tensile test,composite specimens are made of ﬁbers of diﬀerent length (5,10,15,and 20mm)and weight ratio (8,12,16,and 20)were used to calculate the tensile strength.Figures 1and 2show the eﬀect of ﬁber length and weight ratios on tensile strength and modulus of the composite,respectively.Figure 1shows that the increase in ﬁber length and weight ratio increases the tensile strength and modulus upto 15mm ﬁber length and 12%weight ratio.Further increases cause the properties to decrease because of lower ﬁber–matrix adhesion and the quantity of ﬁber content being more than matrix.From Figures 1and 2,the maximum tensile strength and modulus oftheFigure 14.SEM micrograph of tensile fracturedspecimen.Figure 15.SEM micrograph of fractured specimen under flexuralload.Figure 16.SEM micrograph of fractured specimen under impactload.Figure 17.Micrograph of poorinterface.Figure 13.Effect of moisture on fiber length;Fiber wt%–20.Venkateshwaran et al.1625composite are16.39MPa and0.652GPa,respectively for theﬁber length of5mm and12%weight ratio. Flexural strength and modulus for diﬀerentﬁber lengths(5,10,15,and20mm)and weight ratios(8, 12,16,and20)are shown in Figures3and4,respec-tively.It was found that the maximumﬂexural strength and modulus are57.53MPa and8.92GPa,respectively for theﬁber length of15mm andﬁber weight of16%.The results of the pendulum impact test are shown in Figure 5.As theﬁber weight and length increases impact strength also increases upto16%ﬁber weight ratio and then begin to decrease.The maximum impact strength of 2.25J/m was found for theﬁber length 20mm and16%ﬁber weight.Although the variousﬁber lengths and weight per-centage provides the maximum mechanical properties, from Figures10,12,and14it can be concluded that the optimumﬁber length andﬁber weight percentage is 15mm and16%respectively as the properties variation with15mm and16%are negligible when compared to the maximum mechanical properties provided by diﬀer-entﬁber lengths and weight percentage indicated as above.The mechanical properties provided above are better than coir18and palmyra.19Water absorption studyThe eﬀects ofﬁber length and content on the water absorption study are shown in Figures6–13.Figures 6to9show the eﬀect ofﬁber content on the water absorption property of the banana/epoxy composite. It shows that as theﬁber content increases the moisture uptake of the composite also increases.This is due to the aﬃnity of the bananaﬁber towards the moisture. The maximum moisture absorption for the composite is around5%for all length and weight percentage of composite.Figures10to13show the eﬀect ofﬁber length on the water uptake capability of composite.It indicates that the variation of length(5,10,15,and 20mm)does not have much impact as compared with theﬁber content.The moisture absorption percentage of bananaﬁber/epoxy composite seems to be lesser than hempﬁber20andﬂaxﬁber21composite. Fractography studyMicrographs of fractured tensile,ﬂexural,and impact specimens are shown in Figures14–17.Figure14shows the micrograph of fractured surface of specimen under tensile load.It clearly indicates that the failure is due to ﬁber pull out phenomenon.Figure15shows the frac-tured surface of the specimen under bending load. Micrograph also shows the bending ofﬁbers due to the application of load.Figure16shows the failure of the composite under impact load.Further,it also shows the striation occurring on the matrix surface and the presence of hole due toﬁber pull out.Figure17shows the micrograph of20mmﬁber length and20%ﬁber weight composite specimen.It clearly indicates that the clustering ofﬁbers result in poor interface with matrix,and in turn decreases the mechanical properties of the composite.ConclusionBased on theﬁndings of this investigation the following conclusions can be drawn:.The optimumﬁber length and weight ratio are 15mm and16%,respectively for bananaﬁber/ epoxy composite..Moisture absorption percentage of banana/epoxy composite for all length and weight percentage is around5..Also,the moisture uptake capability of the compos-ite is greatly inﬂuenced byﬁber content than length. .SEM image shows that increasing theﬁber content above16%results in poor interface betweenﬁber and matrix.References1.Houston N and Acosta F.Environmental effect of glassfiber reinforced polymers.In:Proceedings of2007Earth Quake Engineering Symposium for Young Researcher, Seattle,Washington,2007.2.Joshi SV,Drzal LT,Mohanty AK and Arora S.Are nat-ural fiber composites environmentally superior to glass fiber reinforced posite Part A2004;35: 371–376.3.Schmidt WP and Beyer HM.Life cycle study on a naturalfiber reinforced component.In:SAE Technical Paper 982195.SAE Total Life-Cycle Conference,1–3 December,1998,Graz,Austria.4.Wotzel K,Wirth R and Flake R.Life cycle studies onhemp fiber reinforced components and ABS for automo-tive parts.Die Angewandte Makromolekulare Chemie1999;272:121–127.5.Corbiere-Nicollier T,Laban BG and Lundquist.Lifecycleassessment of bio-fibers replacing glass fibers as reinforce-ment in plastics.Resour Conserv Recycl2001;33:267–287.6.Pothan LA,Thomas S and Neelakantan NR.Shortbanana fiber reinforced polyester composites:mechanical, failure and aging characteristics.J Reinf Plast Compos 1997;16:744–765.7.Idicula M,Neelakantan NR and Oommen Z.A study ofthe mechanical properties of randomly oriented short banana and sisal hybrid fibre reinforced polyester compos-ites.J Appl Polym Sci2005;96:1699–1709.1626Journal of Reinforced Plastics and Composites30(19)8.Idicula M,Malhotra SK,Joseph K and Thomas S.Dynamic mechanical analysis of randomly oriented short banana/sisal hybrid fibre reinforced polyester pos Sci Technol2005;65:1077–1085.9.Sapuan SM,Leenie A,Harimi M and Beng YK.Mechanical property analysis of woven banana/epoxy composite.Mater Design2006;27:689–693.10.Venkateshwaran N and ElayaPerumal A.Banana fiberreinforced polymer composite-a review.J Reinf Plast Compos2010;29:2387–2396.11.Venkateshwaran N,ElayaPerumal A,Alavudeen A andThiruchitrambalam M.Mechanical and water absorption behavior of banana/sisal reinforced hybrid composites.Mater Design2011;32:4017–4021.12.Sapuan SM and Maleque MA.Design and fabrication ofnatural woven fabric reinforced epoxy composite for household telephone stand.Mater Design2005;26: 65–71.13.Zainudin ES,Sapuan SM,Abdan K and MohamadMTM.Thermal degradation of banana pseudo-stem fibre reinforced unplastisized polyvinyl chloride compos-ites.Mater Design2009;30:557–562.14.Zainudin ES,Sapuan SM,Abdan K and MohamadMTM.The mechanical performance of banana pseudo-stem reinforced unplastisized polyvinyl chloride compos-ites.Polym Plast Technol Eng2009;48:97–101.15.Zainudin ES,Sapuan SM,Abdan K and MohamadMTM.Dynamic mechanical behaviour of bananapseudo-stem filled unplasticized polyvinyl chloride com-posites.Polym Polym Compos2009;17:55–62.16.Uma Devi L,Bhagawan SS and Sabu Thomas.Mechanical properties of pineapple leaf fiber-reinforced polyester composites.J Appl Polym Sci1997;64: 1739–1748.17.Dabade BM,Ramachandra Reddy G,Rajesham S andUdaya kiran C.Effect of fiber length and fiber weight ratio on tensile properties of sun hemp and palmyra fiber reinforced polyester composites.J Reinf Plast Compos 2006;25:1733–1738.18.Harish S,Peter Michael D,Bensely A,Mohan Lal D andRajadurai A.Mechanical property evaluation of natural fiber coir composite.Mater Characterisation2009;60: 44–49.19.Velmurugan R and Manikandan V.Mechanical proper-ties of palmyra/glass fiber hybrid posite Part-A2009;38:2216–2226.20.Dhakal HN,Zhang ZY and Richardson MOW.Effect ofwater absorption on the mechanical properties of hemp fibre reinforced unsaturated polyester composites.Compos Sci Technol2007;67:1674–1683.21.Alix S,Philippe E,Bessadok A,Lebrun V,Morvan V andMarais S.Effect of chemical treatments on water sorption and mechanical properties of flax fibres.Bioresour Technol2009;100:4742–4749.Venkateshwaran et al.1627。

BFRP网格

第51卷第4期2020年4月中南大学学报(自然科学版)Journal of Central South University (Science and Technology)V ol.51No.4Apr.2020BFRP 网格−PCM 薄面黏贴加固钢筋混凝土板抗弯性能丁里宁1，贺卫东2,3，汪昕2,3，程方2,3，吴智深2,3(1.南京林业大学土木工程学院，江苏南京，210037；2.东南大学土木工程学院，江苏南京，210096；3.东南大学城市工程科学技术研究院，江苏南京，210096)摘要：针对老旧桥梁桥面板出现结构损伤与材料老化，结合玄武岩纤维增强复合材料(BFRP)网格与聚合物砂浆(PCM)提出一种新的加固技术以提升钢筋混凝土板的抗弯性能。

首先，采用双剪试验研究BFRP 网格与混凝土界面的黏结荷载，共制备18个试件，试验变量包括网格种类、网格厚度、PCM 种类以及界面剂；其次，浇筑6块钢筋混凝土板，通过四点弯曲试验系统地分析网格种类、网格厚度、网格布置方式以及PCM 种类对加固板抗弯性能的影响。

研究结果表明：界面剂能有效提高BFRP 网格与混凝土之间的黏结荷载；当BFRP 网格与混凝土表面的黏结长度大于有效黏结长度时，BFRP 网格强度利用率达到90%以上，黏结荷载高于相同情况下玄武岩纤维布/BFRP 板与混凝土的黏结荷载；BFRP 网格与PCM 形成的薄面加固层能显著提高钢筋混凝土板的开裂荷载、屈服荷载以及极限荷载，同时减小最大裂缝宽度并改善裂缝分布；在整个加载过程中，BFRP 网格−PCM 薄面加固层与混凝土板协同变形，加固板最终发生混凝土压碎或FRP 网格断裂破坏，并未出现剥离破坏；传统钢筋混凝土构件抗弯承载力计算方法适用于预测BFRP 网格加固后板的抗弯承载力。

关键词：BFRP 网格；PCM ；黏结性能；钢筋混凝土板；抗弯加固中图分类号：TU528.572文献标志码：A开放科学(资源服务)标识码(OSID)文章编号：1672-7207（2020）04-1085-12Flexural behavior of reinforced concrete slabs strengthened withBFRP grids and PCMDING Lining 1,HE Weidong 2,3,WANG Xin 2,3,CHENG Fang 2,3,WU Zhishen 2,3(1.School of Civil Engineering,Nanjing Forestry University,Nanjing 210037,China;2.School of Civil Engineering,Southeast University,Nanjing 210096,China;3.International Institute for Urban Systems Engineering,Southeast University,Nanjing 210096,China)Abstract:In view of the old bridge decks which suffer from structural damage and material degradation,a new strengthening technique for improving the flexural behavior of reinforced concrete(RC)slabs was proposed by combining basalt fiber reinforced composite(BFRP)grid and polymer cement mortar(PCM).Firstly,the bond loadDOI:10.11817/j.issn.1672-7207.2020.04.023收稿日期：2019−06−19；修回日期：2019−07−30基金项目(Foundation item)：国家重点研发计划项目(2017YFC0702000)；江苏省自然科学基金资助项目(BK20150886)(Project(2017YFC0702000)supported by the National Key Research and Development Program of China;Project(BK20150886)supported by the Natural Science Foundation of Jiangsu Province)通信作者：汪昕，博士，教授，从事高性能纤维增强复合材料研发与应用研究；E-mail ：***************.cn第51卷中南大学学报(自然科学版)was studied according to double-lap shear test with20specimens,and the variable parameters included the grid type,grid thickness,PCM type and interface treating agent.Secondly,6slabs were fabricated and tested in the four point flexural experiments.The effects of the grid type,grid thickness,grid layout and PCM type on the flexural behavior of strengthened slabs were systematically analyzed.The results show that the interface treating agent can effectively improve the bond load between the BFRP grid and concrete.When the bond length is larger than the effective bond length,the strength utilization ratio of the BFRP grid is more than90%,and the bond load is higher than that of the basalt fiber sheet/BFRP plate under the same condition.The thin strengthening layer formed by the BFRP grid and PCM can significantly increase the cracking load,yield load and ultimate load of the strengthened slabs,reduce the maximum cracks width and improve the distribution of cracks.During the whole loading process,the strengthening layer and the slabs deform in coordination,and the slabs finally suffer from concrete crushing or FRP grid rupture without debonding.In addition,the traditional calculation method of flexural capacity for RC members is suitable for that of slabs strengthened with BFRP grid.Key words:basalt fiber reinforced composite(BFRP)grid;polymer cement mortar(PCM);bond behavior; reinforced concrete(RC)slab;flexural strengthening对于老化或因外力损伤的混凝土结构，通过加固恢复结构承载力并延长使用寿命具有较大经济效益。

EFFECTOFANTANAN（...

BIOTROPIA NO. 24, 2005 : 46 - 53EFFECT OF ANTANAN (CENTELLA ASIATICA) AND VITAMIN C ONTHE BURSA OF FABRICIUS, LIVER MALONALDEHIDE ANDPERFORMANCE OF HEAT-STRESSED BROILERSENGKUS KUSNADI1, REVIANY WlDJAJAKUSUMA2, TOHA SUTARDI3,PENI.S.HARDJOSWORO4 and ARIFIEN HABIBIE5'Department of Animal Production.Faculty of Animal Husbandry, AndalasUniversity(Unand), Padang, Indonesia 2Department of Physiology and Pharmacology,Faculty of Veterinary Medicine,Bogor Agriculture University(IPB), Bogor, Indonesia 3Department of Animal Nutrition & Feed Science, Faculty of Animal Husbandry,Bogor Agriculture Universirty(IPB), Bogor, Indonesia 4Department of Animal Production, Faculty of Animal Husbandry,Bogor Agriculture University (IPB), Bogor, Indonesia1 Deputy Assistant for Agroindustry-Jakarta, Coordinating Ministry for Economic Affairs,Jakarta, IndonesiaABSTRACTHigh environmental temperatures may cause heat stress in poultry. This may increase water consumption, decrease feed consumption and in rum, decrease productivity level. In addition, high temperature contributes to oxidative stress, a condition where oxidant activity (free radicals) exceeds antioxidant activity. In our research, antanan (Centelta asiatica) and vitamin C were utilized as anti heat-stress agents for heat-stressed broilers. We used 120 male broilers 2-6 weeks old, kept at 31.98 ± 1.94 °C during the day and 27.36 ± 1.31 °C at night. The data collected were analyzed with a completely randomized factorial design of 2 x 3 (2 levels of vitamin C, 3 levels of antanan at 4 replications) and continued with the contrast-orthogonal test when significantly different. The results indicate that the treatments of 5 and 10% of antanan with or without 500 ppm of vitamin C and vitamin C alone significantly (P<0.05) decreased the heterophil/lymphocyte (H/L) ratio and liver malonaldchydc (MDA). These treatments, however, significantly (P<0.05) increased the bursa of Fabricius weight, feed consumption and body weight gain. It could be concluded that basal ration administered with 5% antanan and 500 ppm vitamin C could effectively prevent broilers from heat stress. The results support the conclusion that a basal ration supplemented with 5% antanan and 500 ppm of vitamin C or their combinations, effectivelly reduces heat stress in broilers.Key words : Heat stress/ Centella asiatica I Vitamin CINTRODUCTIONHigh environmental temperatures may result in the accumulation of body heat load so that the body suffers from heat stress. As one of the homeothermic species, poultry could maintain their body temperature relatively constant by increasing respiration rate and water consumption and/or decreasing feed consumption. As a result, their growth rate and productivity will decrease.46BIOTROPIA NO. 24, 2005May and Lott (2001) showed that body weight gain of 3 to 7-week-old male broilers raised at a temperature of 30°C was 1869 g significantly lower than for those raised at 22°C with body weight gains of 2422 g and feed conversion decreased from 3.28 to 2.54. The lower performances of broilers raised at high temperatures may have occurred as a result of lowered secretion of thyroid hormones (Geraert et al. 1996), decreased blood hemoglobin and hematocrit levels (Yahave/a/. 1997), or increased excretion of some minerals (Belay et al. 1992) and some amino acids (Tabiri et al. 2001).In addition, heat stress may also cause oxidative stress in the body and develop abundant free radicals, promoting the occurrence of peroxidation of membrane lipids and hence attacking DNA and protein membranes (Rahman 2003). Takahashi and Akiba (1999) indicated that feeding oxidized lipids to broilers significantly decreased feed consumption, body weight gain, plasma vitamin C, and plasma a-tocopherol. In fact, the results were followed by an increase in plasma malonal-dehyde (MDA) and blood heterophyl/lymphocytes (H/L) ratios as biological indices of stress in avian species.Antanan/pegagan (Centella asiatica (L.) Urban), one of the medicinal plants containing active materials such as asiatic acid, asiaticoside, and madecasic, is readily available and evidently eliminates stress in rats (Kumar and Gupta 2003). Shukla et al. (1999) reported that placing asiaticoside on rats wound increases curability and accelerates enzymatic and non-enzymatic antioxidant activities of new-growing tissues. In addition, vitamin C reportedly eliminated cold stress (Sahin and Sahin 2002) and heat stress in poultry (Puthpongsiriporn et al. 2001) and showed synergism with some active materials contained in antanan (Bonte et al. 1994). With this in mind, we have examined the effect of antanan (Centella asiatica) and vitamin C on the bursa of Fabricius, liver malonaldehide and performance in heat-stressed broilers.MATERIALS AND METHODSThis research used 2 to 6-week-old male broilers placed in several pens located in an open poultry house. Each pen was flitted with a 40-Watt lamp and a zinc-plate backing functioning as a heat reflector. Temperature and relative humidity measurements obtained at noon and afternoon were 31.98 ± 1.28°C and 78.82 ± 5.43%, respectively. Temperature and relative humidity measurements at night and early morning were 27.36 ± 0.88°C and 86.23 ± 3.93%, respectively. The levels of 500 ppm vitamin C and 10% antanan (all plant parts) of ration used were established during preliminary trials. Vitamin C was dissolved in drinking water and served in the morning, two hours after the broilers received their last waterfeeding.47Effect of antanan (Centella asiatica) and vitamin C ‐ Engkus Kusnadi et al.One‐hundred‐and‐twenty‐two‐week‐old male broilers were randomly allocated into 24 pens, 5 broilers each. Antanan (5% and 10%) was mixed with other ingredients to make three different rations as follows: 1) The control ration contained the calory as metabolizable energy (ME) 3245.02 kcal/kg and 20.84% crude protein , 2) A5 = 5% antanan contained ME 3222.95 kcal/kg and crude protein 20.91%, and 3) A10 = 10% antanan contained ME 3202.87 kcal/kg and crude protein 20.99%. The ration formulation and nutrient composition of treatments are presented in Table 1.The broilers were subjected to six treatments, 20 broilers each, as follows:1) K (Control)/ration neither contained antanan nor vitamin C.2) A5/ration was supplemented with 5% antanan3) AlO/ration was supplemented with 10% antanan4) C, drinkwater contained 500 ppm vitamin C5) A5C, combination of A5 and C, and6) A10C, combination of A10 and C48BIOTROPIA NO. 24, 2005Variable measurements:1) Relative bursa of Fabricius weight taken from 4-week-old broilers, by weighing the organ anddivided by body weight (Puvadolpirod and Thaxton 2000).2) Heterophyl/lymphocyte ratio was taken from 4-week-old broilers, by hemo-cytometermethod. Blood was diluted 1:101 in a red blood cell pipette with Nat and Herrick diluent. The total leucocyte count includes heterophils, lymphocytes, monocytes, basophils, and eosinophils is divided by the number of lymphocytes.3) Liver malonaldehyde (MDA) taken from 6-week old broilers, by measuring the thiobarbituricacid (TEA) value using Tarladgis method (Apriyantono et al. 1989). Destilate from liver sample with pH: 1.5, is added to the TBA reagents, covered, mixed, and incubated in boiling water bath for 35 minutes. After cooling, the absorbance of filtrate (D) was determined at 528 nm wave length. The TBARs values = 7.8 D were expressed as mg/kg of malonaldehyde per kg of tissue.4) Feed consumption, body weight gain, and feed conversion are measured for 4 weeks (from 2to 6-week-old broilers). Feed consumption was determined by weighing the given ration minus the leftover. Body weight gain was measured by weighing the final body weight at 6 weeks old minus the body weight at 2 weeks old. Feed conversion was measured by dividing feed consumption with body weight gain.Statistical analysisThe collected data were analyzed using a completely randomized factorial design (CRD) 2 x 3 (2 levels of vitamin C i.e. 0 and 500 ppm and 3 levels of antanan i.e. 0, 5 and 10% of rations at 4 replications), and where applicable, continued with orthogonal contrast test according to Steel and Torrie (1980).RESULTS AND DISCUSSIONThe results of the effect of antanan and vitamin C administration on bursa of Fabricius weight, H/L ratio and liver MDA contents are presented in Table 2. The data for feed consumption (FC), body weight gain (BWG), and feed conversion are presented in Table 3.From Table 2, the average relative of 4 - week bursa of Fabricius weight for controls (K) is significantly lower than those treated with A5, A10, C, A5C, or A10C. The bursa of Fabricius weight is similar for all treatments from A5 to A10C.49Effect of antanan (Centella asiatica) and vitamin C ‐ Engkus Kusnadi et al.These results suggest that antanan, vitamin C, or their combinations increase burs of Fabricius weight of broilers that suffered heat stress.The ability of antanan to stimulate lymphoid gland weight was reported i stressed rats by Sharma et al. (1996). Antanan contains phenol compounds th< potentially can prevent peroxidation of lipid membranes including T‐ and E lymphocyte membranes. T‐lymphocytes produce cellular immunities while E lymphocytes produce humoral immunities produced by the bursa of Fabricius in bir species. Phenol compounds of tea extracts were potentially capable of stimulatin the production of lymphoid cells in rats (Murtini et al. 2003). On the other hanc vitamin C acts, as a water‐soluble antioxidant capable of protecting lymphocyte from suffering heat stress (Puthpongsiriporn et al. 2001). As a result, the number o circulating lymphocytes increased so that the H/L ratio decreased.Table 2 shows a relationship between the increase of the bursa of Fabriciu weight and decrease in H/L ratio because the bursa of Fabricius is a lymphoid orgai producing lymphocytes. Thus, the smaller the bursa of Fabricius size, the fewe lymphocytes will be produced, and in turn, the higher the H/L ratio will be. Increase of the relative lymphoid organ weight occurred as a result of antanan feeding whicl was demonstrated by Sharma et al. (1996), while increase of the relative bursa o Fabricius weight as a result of supplementing vitamin C to broilers was reported b] Anim et al. (2000).Heat stress generating oxidative stress may increase MDA content as a result of lipid peroxidation, especially for unsaturated fatty acids of membrane cells. Feeding50BIOTROPIA NO. 24, 2005antioxidants, i.e. antanan and vitamin C, significantly decreases liver MDA content. Besides of being able to relieve free radicals by releasing an electron and a proton (a hydrogen ion), phenol compounds are also able to provide a chelating effect in such a way that phenols bind to transition ions. Unbound metals might increase free radicals (Pietta 2000). In addition, phenol compounds are characterized by flavonoids that are able to decrease fluidity of cell membranes so that it may decrease diffusion of free radicals and MDA contents. This is also true for vitamin C, a water-soluble antioxidant with 2 hydroxyl groups at €2 and €3 that are readily oxidized (Sediaoetama 1987).In addition, it is unmistakable that feeding antanan and vitamin C increases feed consumption and body weight gain of broilers over four weeks (2-6 weeks of age) but not for feed conversion (Table 3). This agrees with the reports of Anim et al. 2000) for broilers and Sharma and Sharma (2002) for rats suffering from stress. Antanan contains antioxidants such as phenol compounds that are capable of eliminating oxidative stress processes (Blokhina 2000), as is apparent from the decrease of H/L ratios, liver MDA levels and increase of bursa of Fabricius weights reported here.CONCLUSIONSFeeding antanan or vitamin C or the combination of antanan and vitamin C increases bursa of Fabricius weight, feed consumption, and body weight gain but decreases H/L ratio and liver MDA levels. The combination of 5% antanan and51Effect of antanan (Centella asiatica) and vitamin C — Engkus Kusnadi et al.vitamin C tends to increase feed consumption and body weight gain and , therefore this treatment tends to be very effective in alleviating heat stress in broilers.ACKNOWLEDGEMENTSThe authors wish to thank the Department of Higher Education, Nations Department of Education, Republic of Indonesia and SEAMEO - SEARCA Regional Center for Graduate Study and Research in Agriculture, College, Lagun 4031 Philippines for their financial support.REFERENCESAnim AJ, TL. Lin, PY. Hester, D. Thiagarajan, BA. Watkins and CC. Wu. 2000. Ascorbic aci supplementation improved antibody response to infectious bursal disease vaccination in chickens Poultry Sci. 79: 680-688. Apryantono.A, D.Fardiaz, NL.Puspitasari, Scdarnawati and S.Budiyanto. 1989. Analisis Pangar Departcmen Pcndidikan dan Kcbudayaan Dircktorat Jcnderal Pcndidikan Tinggi Pusat Anta Universitas Pangan dan Gizi Institut Pcrtanian Bogor.Belay T, Wicmusz CJ and RG. Teeter. 1992. Mineral balance and urinary and fecal mineral excrctioi profile of broilers housed in thcrmoncutral and heat-distressed environments. Poultry Sci. 71: 104 - 1047.Blokhina O. 2000. Anoxia and oxidativc stress: Lipid pcroxidation, mitochondria! functions in plant antioxidant status and mitochondria! functions in plantshttp://ethesis.helsinki.fi/iulkaisut/mat/bioti/vk/blokhina/anoxiaan.html. [20 Dcscmbcr 2003].Bonte F, Dumas M, Chaudagnc C and A. Mcybcck. 1994. Influence of asiatic acid, madccassic acid, am asiaticoside on human collagen I synthesis. Planta Med. 60: 133 - 135.Geraert PA, Padilha JCF and S. Guillaumin 1996. Metabolic and endocrine changes by chronic hca exposure in broiler chickens: biological and endocrinological variables. Br. J. Nutr.75:205-216.Gross WB and HS. Siegel. 1983. Evaluation of the Heterophil/Lymphocyte Ratio as a Measure of Stres in Chickens.Avian Dieseasc.27: 972 - 979.Kumar VMH and YK. Gupta. 2003. Effect of Centella asiatica on cognition and oxidative stress in ai intracerebroventricular streptozotocin model of Alzheimers disease in rat. Clin Exp Pharmaco Physiol 30: 336-342.May JD and BD. Lott. 2001. Relating weight gain and feed:gain of male and female broilers to rearini temperature.Poultry Sci 80: 581-58444.Murtini S, Murwani R, Bunawan A, Handharyani E and F. Satrija. 2003. Effects of inoculation route am dose level of tea mistletoe (Scurrula oortiana) stem extract on the development of lymphoi< follicle of bursa fabricius in chick embryonated eggs. International Symposium on Biomedicincs 18lh and 19th September 2003. IPB.52BIOTROPIA NO. 24, 2005Pietta PG. 2000. Flavonoids as antioxidants. Reviews. J Nat Prod 63: 1035-1042.Puthpongsiriporn U, Scheidelcr SE, Sell JL and MM. Beck. 2001. Effects of vitamin E and C supplementation on performance, in vitro lymphocyte proliferation, and antioxidant status of laying hens during heat stress.Poultry Sci 80: 1190-1200.Puvadolpirod S and JP. Thaxton. 2000. Model of physiological stress in chickens 1. Response Parameters. Poultry Sci 79: 363-369.Rahman.I. 2003. Oxidative stress, chromatin remodelling and gene transciption in inflammation and chronic lung desease. J.Biochcm. Mol. Biol. 36: 95-109.Sahin K and N. Sahin. 2002. Efcct of chromium picolinatc and ascorbic acid dietary supplementation on nitrogen and mineral excretion of laying hens reared in low ambient temperature (7 °C). Acta Vet Brno 71: 183-189. Sediaoetama, AD. 1987. Vitaminologi. Jakarta: Balai Pustaka.Sharma DNK, Khosa RL, Chansouria JPN and N. Saha. 1996. Antistrcss activity of Tinospora cordifolia and Centella asiatica extracts. Phytotherapy-Rescarch 10: 181 - 183.Sharma J and R. Sharma. 2002. Radioprotcction of Swiss albino mouse by Centella asiatica extract.Phytotherapy-Research 16: 785 - 786.Shukla A, Rasik AM, and BN. Dhawan. 1999. Asiaticoside-induced elevation of antioxidant levels in healing wounds. Phytotherapy-Research 13: 50-54.Steel ROD and JH. Torrie. 1980. Principles and procedures of statistic, second ed, Graw-Hall, Book Comp, New York.Tabiri HY, Sato K, Takahashi K, Toyomizu M, and Y. Akiba. 2000. Effects of acute heat stress on plasma amino acids concentration of broiler chickens. Jpn Poult Sci 37: 86-94.Takahashi K and Y. Akiba. 1999. Effect of oxidized fat on performance and some physiological responses in broiler chickens. J Poult Sci 36: 304-310.Yahav S, Straschnow A, Plavnik I and S. Hurwitz 1997. Blood system response of chickens to changes in environmental temperature. Poultry Sci 76: 627 - 633.53。

Effect of substitution of oat hulls for traditional fiber source on

Effect of substitution of oat hulls for traditional ﬁber source on digestion and performance of fattening rabbitsS.Liangzhan a ,J.Xiang a ,Z.Caixia,F.Zhaohui and L.Fuchang †College of Animal Science and Technology,Shandong Agricultural University,Tai ’an 271018,P R China(Received 7April 2015;Accepted 3October 2016;First published online 8November 2016)The objective of this study was to evaluate the use of oat hulls (OH)to substitute traditional ﬁber (a mixture of rice hulls and mugwort (RHM)leaf)in the diets of fattening rabbits by examining on its effect on the growth performance,coef ﬁcient of total tract apparent digestibility (CTTAD)of nutrients,gastrointestinal tract development,cecum fermentation and carcass traits.A total of 160mixed sex Hyla commercial meat rabbits (40/treatment)were used to study the effects of including OH in the diet from 30to 80days of age.A control diet based on RHM and containing 175.2g crude ﬁber and 169.7g CP/kg was included.Growth performance and CTTAD of nutrients were recorded from day 35to day 80and day 74to day 80,respectively,whereasgastrointestinal tract development,cecum fermentation and carcass traits were determined at day 80.Increasing concentrations of OH in the diet increased average daily feed intake (P =0.0018),but have no effects on average daily gain and feed conversion ratio (P >0.05).Moreover,the 150g/kg OH diet decreased the relative weight of full cecum and cecal content (P <0.05),but did not affect other gastrointestinal organs.The CTTAD of NDF and gross energy decreased with the inclusion of OH (P <0.05).No effects of CTTAD of ADF,ADL,dry matter,CP and ether extract were observed (P >0.05).The concentrations of total volatile fatty acid,acetic and butyric acids were greater in rabbits fed the lower levels of OH (0to 100g/kg)compared with higher rate(150g/kg;P <0.05).However,the proportions of acetic,propionic and butyric acids were not affected by treatments (P >0.05).Furthermore,no signi ﬁcant effect on the ratios of acetic/(propionic +butyric)was observed (P >0.05).Hot carcass weight,pH (45min,24h),lightness,redness,yellowness,24-h drip loss of longissimus lumborum muscles were not affected by diet OH (P >0.05).However,dressing out percentage increased with higher (150g/kg)inclusion of OH.It is concluded that OH can be included in rabbit diets at levels up to 100g/kg,but negative effect on digestion and performance were observed with the increasing of OH (150g/kg).Keywords:cecum fermentation,carcass traits,growth performance,oat hulls,rabbitImplicationsDietary ﬁber is the main constituent of rabbit feed,usually ranges from 150to 500g/kg,but the price of traditional ﬁber like alfalfa,mugwort and rice hull are rising sharply.There-fore,alternatives are required to produce balanced pelleted feeds using local raw materials,available at a lower price.This study aimed to assay that if oat hulls (OH)can satisfactorily replace traditional ﬁber source in diets for growing-fattening rabbits.IntroductionThe rabbit is a small-sized mono-gastric herbivorous animal and ﬁber is one of the main constituents of diets forintensively reared rabbits (de Blas et al .,1999).The type and inclusion level of ﬁber sources determine the quality of rabbit diets (de Blas et al .,1999).Rice hulls and mugwort (RHM)is the ﬁber source common utilized in diet formulation for the fattening rabbit,but the price of mugwort is rising sharply.Therefore,alternatives are required to produce balanced pelleted feeds using local raw materials,available at a lower price.Oats (Avena sativa L.)are a major cereal worldwide and the sixth cereal grain after maize,rice,wheat,barley and sorghum (Food and Agriculture Organization,2011).Oat cultivation yields two main by-products:oat straw,the vegetative residue after grain harvest,and OH.OH is con-sidered as a source of ﬁber for ruminants and rabbits and is often compared with a low-quality roughage in terms of nutritive value (Fraser et al .,2004).As a source of ﬁber,OH is a classic compound feed ingredient in commercial rabbit feeding,Maríaet et al .(2007)tested the effect of OH on†E-mail:chlf@a These two authors contributed equally to this work.Animal (2017),11:6,pp 968–974©The Animal Consortium 2016doi:10.1017/S1751731116002263968digestion,intestinal microbiota and performance in 25-day-old weaned rabbits.Martínez et al.(2013)observed the effect of OH on ileal apparent digestibility and cecal environment in17to35-day-old rabbits.David and John (1978)observed the effect of OH on New Zealand White rabbits between5and8weeks old,but the information related to the effect of the OH on fattening rabbits is scarce and insufﬁcient to formulate practical recommendations. Thus,OH use as rabbit feed ingredients merits further investigation.The objective of this study was to evaluate the use of OH to substitute traditionalﬁber in the diets of fattening rabbits by examining its effect on the growth performance,coefﬁ-cient of total tract apparent digestibility(CTTAD)of nutrients, gastrointestinal tract development,cecum fermentation and carcass traits.Material and methodsThe study was approved by the Animal Welfare and Healthy Breed committee of Shandong province(Shandong,China) and performed in accordance with the‘Guidelines for Experimental Animals’of the Ministry of Science and Technology(Beijing,China).Animal and dietA total of16030-day-old weaned Hyla commercial meat rabbits(male–female ratio of1:1)with average BWs (550±50g)were used in this study.All rabbits were randomly divided into four groups(n=40,equal numbers of males and females per group)and fed with different experimental diets.Rabbits were individually housed in self-made metabolism cages(60×40×40cm).The rabbits were provided with free access to water.During the trials,rabbitswere housed in a closed and ventilated building in which the temperature was maintained at17°C to25°C and the relative humidity ranged from50%to60%.A cycle of12h of light:dark was used throughout this trial.The diets(see Table1)were formulated according to the values for growers from National Research Council(1989) and de Blas and Mateos(1998)and were pelleted by the use of pressure.The diameter of each pellet was4mm.The OH supplementation levels of the four experimental diets were0, 50,100and150g/kg diet(as-fed basis),respectively. Experimental proceduresThe feed was offered ad libitum and reﬁlled at0830and 1730h daily,residual feed was collected from the cages simultaneously.The total experiment consisted of a5-day adjustment period followed by a45-day experimental period including a7-day(day74to day80)collection of feces.In addition,40additional rabbits at day74to day80of age were used in a digestibility trial to determine the CTTAD of CP,gross energy(GE),dry matter,ether extract(EE),NDF, ADF and ADL of the diets,following the European reference method(Perez et al.,1995).Feces and residual feed were collected from the metabolism cages.The CTTAD of CP,GE, EE,NDF and ADF,ADL of the diets,following the European reference method(Perez et al.,1995).Individual weight (with restriction of food and water)was measured at the beginning and end of the trial and the average daily gain (ADG)was calculated.The average daily feed intake(ADFI) was calculated according to total of food intake divided by total experimental days.The feed conversion ratio(FCR)was then calculated.The ADG,ADI and FCR calculations did not include the5-day adjustment period.At the end of the trial,eight rabbits per group were selected for the further examination based on the following criteria:equal ratio of males:females and the average BW of the eight rabbits was equal to the average BW of entire treatment group.Selected animals were electrically stunned (70V,pulsed direct current,50Hz for5s)and killed by cervical dislocation at1700h.BW and carcass weight were measured.The hot carcass weight(weight of the carcass 15to30min after slaughter)and dressing out percentage were calculated.Meanwhile,the whole longissimus lumborum(LL, between theﬁrst and seventh lumber vertebra)was removed Table1Ingredients and chemical composition of the experimental diet (g/kg,as-fed basis)Oat hulls(g/kg)Items050100150 IngredientMaize100100100100 Wheat bran150150150150 Corn germ meal100100100100 Soybean meal50505050 Alfalfa80808080 Soybean oil10101010 Rice hulls80604020 Soybean stalk10101010 Oat hulls050100150 Sunﬂower meal100100100100 Wheat germ80808080 Mugwort leaf1501209060 Premix150505050 Total1000100010001000 Chemical compositionCP169.7166.5163.3160.0 Crudeﬁber175.2174.3174.8175.2 Ether extract30.130.230.330.3 NDF363.3374.4386.5398.6 ADF208.1204.9203.5202.1 ADL53.852.75251.3 Calcium10.010.110.09.9 Total phosphorus 6.3 6.2 6.1 6.0 Digestible energy29.369.419.399.38 Digestible protein2130.0127.4124.9124 The premix provided the following per kg of diet:Lys1.5g;Met1.5mg; Cu50mg;Fe100mg;Zn50mg;Mn30mg;Mg150mg;I0.1mg;Se0.1mg; vitamin A12000IU;vitamin D800IU;vitamin E50g.2Calculated from digestibility coefﬁcients obtained in the digestibility trial.Effect of oat hulls for rabbit969from the right side of each carcass.The LL was then divided into three sub-samples.One sub-sample was utilized for pH measurements at45min and24h.The second sub-sample was utilized for the measure of the muscle color(L*,a*and b*)and third sub-sample was utilized for the measure of cooking loss and shear force.The pH was measured on the LL with a Crison MicropH2001(Crison Instruments,Barcelona, Spain)provided with a combined electrode and an automatic temperature compensator.The pH was measured by insert-ing the probe into the muscle and the values were obtained considering the average of three readings per meat sample. Meat color was measured at room temperature(20°C)using a portable Minolta CR-331CMinolta Colorimeter(Min-olta Camera,Osaka,Japan)with D65illuminant and2°standard observer.The color values were obtained considering the average of three readings per meat sample.As for the cooking loss,each sample of the LL was weighed,placed in a vacuum sealed polyethylene bag,totally immersed in a constant temperature water bath and cooked at80°C for1h to calculate the cooking losses.After cooking,the samples were cooled under running water for30min.The samples were then removed from the bags,blotted and weighed.The cooking losses were expressed as a percentage of the initial weight.The LL,cooked as described above,were cut into rectangular cross-section strips(1cm thick×1cm wide×3cm along theﬁber)and were sheared perpendicular to the muscleﬁber direction using an Instron5543equipped with a Warner–Bratzler shear device(Instron Corporation,MA,USA) and cross-head speed set at100mm/min.The maximum force measured to shear the strips was expressed as Newtons. After slaughter,the cecum was removed and weighed both with and without its contents.The following was calculated: cecum ratio(g/g)=cecum weight(g)/BW(g)and the cecum content ratio(g/g)=cecum content weight(g)/BW(g). Chemical analysesThe protein content was obtained by the measuring nitrogen content of feeds and feces by the methods outlined by Kjeldahl(Association of Ofﬁcial Analytical Chemist(AOAC), 1995),and AOAC(1995)for crudeﬁber.Analysis ofﬁber components was performed according to Goering and Van Soest(1970)and more recent modiﬁcations to the NDF procedure(Van Soest et al.,1991).EE was measured in a Soxhlet extractor.The energy levels of the feed and feces were measured in a bomb calorimeter.The pH value of cecal content was determined from each rabbit45min postmortem with a pH meter equipped with a pH probe(Crison MicropH2001).The samples of cecal contents were then centrifuged at25000g at0°C for10min.The NH3-N concentration and volatile fatty acid(VFA)of the supernatant were measured.NH3-N concentration was measured by the technique of Weatherburn(1967)and determined via spectro-photometer.The VFAs were measured by gas chromatography, with a gas column:free fatty acids and phenols10%H3PO4,1% acid-washed chromosorb W,100to120mesh.The carrier gas was N2with aﬂow rate of40ml/min;H2and airﬂows to the detector were set at a rate of60ml/min.Injector and detector temperatures were maintained at250°C.The oven temperature was set to150°C.Statistical analysisThe experiment was conducted using a completely randomized design with four treatments,40replicates/treatment and one rabbit per replicate.All data are expressed as means and analyzed using linear models ANOVA(GLM)procedure (SAS,9.3;SAS Institute Inc.,Cary,NC,USA).For growth performance analysis,n=40/treatment,for CTTAD,gastro-intestinal tract development,cecum fermentation and carcass traits and meat qualities analysis,n=8/treatment.Differences among treatments were examined by Duncan’s multiple range test and were considered to be signiﬁcant at P<0.05. ResultsThe effect of dietary oat hulls levels on growth performance The growth performances of the experimental rabbits reared under different OH levels are presented in Table 2. Throughout the experiment,the health status of rabbits was good,as only one rabbit died in group feed0g/kg OH and only two in the150g/kg OH group had transitory diarrhea. These three rabbits were excluded from the evaluation.ADFI increased signiﬁcantly as OH levels increased,a higher feed intake was observed in rabbits fed the150g/kg OH diet compared with diets with lower OH concentrations (P<0.05).However,no signiﬁcant difference was observed for FCR and ADG(P>0.05).The effect of dietary oat hulls levels on gastrointestinal tract developmentTable3shows the effect of different OH dietary treatments on the relative weight of digestive organs and their contents. There are no variations in the relative weight of stomach, intestine and their contents.However,the relative weight of full cecum and cecal contents decreased with the increase in OH levels(P<0.05).The effect of dietary oat hulls levels on coefﬁcient of total tract apparent digestibility of nutrientsFrom the data of Table4,we can conclude that the increase in OH had a signiﬁcant effect on the CTTAD of ADF and GE, Table2The effect of oat hulls(OH)concentration on the growth performance of experimental rabbitsOH(g/kg)Items050100150RMSE P-value ADFI(g/day)127.4a129.5a133.8ab137.4b 5.530.0018 ADG(g/day)41.842.843.043.8 1.970.0734 FCR 3.05 3.02 3.11 3.140.190.7933 RMSE=root mean square error;ADFI=average daily feed intake;ADG= average daily gain;FCR=feed conversion ratio.a,b Within a row,means without a common superscript letter differ(P<0.05).Liangzhan,Xiang,Caixia,Zhaohui and Fuchang 970both ADF and GE were decreased in the group feed150g/kg OH(P<0.05),but the CTTAD of CP,EE,ADF,ADL,dry matter and GE were not affected(P>0.05).The effect of dietary oat hulls levels on cecum fermentation The values of cecal pH,ammonia N and VFA concentrations and proportions are presented in Table5.Cecal pH was signiﬁcantly inﬂuenced by diet(P<0.05),but ammonia N in the cecal content was not(P>0.05).Although,acetic acid was the predominant VFA(72.72%to75.61%of the total) followed by butyric and propionic acids,it was not affected by diet(P>0.05).The absolute concentrations of VFAs (namely acetic and butyric acids)and total VFA concentra-tions were affected by treatments(P<0.05).High OH diet signiﬁcantly decreased the concentration of total VFAs, acetic acid and butyric acid(P<0.05).No signiﬁcant dif-ferences in propionic diets were observed(P>0.05).Pro-portions of acetic,propionic and butyric acids were not affected by treatments(P>0.05).Moreover,treatments had no signiﬁcant effect on the ratios of acetic acid/ (propionic+butyric acids).The effect of dietary oat hulls levels on carcass traits and meat qualitiesThe carcass traits and meat quality data are given in Table6. There were no differences among the groups in hot carcass weight(P>0.05).However,dressing out percentage increased with increasing in OH levels(P<0.05).Further, the pH(45min),pH(24h),shear force,cooking loss and physical traits(lightness,redness,yellowness)of LL muscles were not affected by the inclusion of OH in the diet (P>0.05).DiscussionThe effect of dietary oat hulls levels on growth performance Dietaryﬁber has been known to affect rabbit growth performance but the effects are largely dependent on the source ofﬁber due to its highly variable ligniﬁcation and cell wall complexity and different hemicelluloses con-stituents(Gidenne et al.,1992;Carabaño et al.,2001;Table3The effect of oat hulls(OH)concentration on thegastrointestinal tract development of experimental rabbits(%BW)OH(g/kg)Items050100150RMSE P-valueFull stomach 5.82 6.00 5.44 4.920.95110.1313Empty stomach 1.39 1.47 1.45 1.330.13530.1700Stomach content 4.43 4.53 3.99 3.600.92400.1774Full small intestine 4.76 4.55 4.40 4.330.51730.3545Empty small intestine 3.30 3.40 3.19 3.200.41290.7345Small intestine content 1.47 1.16 1.21 1.130.34700.2089Full cecum7.40a7.12a 6.78ab 6.50b0.69270.0326Empty cecum 1.49 1.55 1.47 1.410.15600.3605Cecal content 5.92a 5.64a 5.23ab 5.09b0.62010.0474RMSE=root mean square error.a,b Within a row,means without a common superscript letter differ(P<0.05).Table4The effect of oat hulls(OH)concentration on the coefﬁcient oftotal tract apparent digestibility of experimental rabbitsOH(g/kg)Items050100150RMSE P-ValueCP0.7660.7650.7650.7750.04410.8206Ether extract0.9750.9730.9740.9720.01050.9716NDF0.284a0.251ab0.215c0.212c0.0207<0.0001ADF0.2820.2780.2550.2520.05320.9407ADL0.0490.0740.0520.0580.01620.9953Dry matter0.6550.6370.6550.6040.03360.3287Gross energy0.580a0.566a0.549ab0.526c0.08780.0159RMSE=root mean square error.a,b,c Within a row,means without a common superscript letter differ(P<0.05).OH(g/kg)Items050100150RMSE P-valuepH 6.19a 6.32ab 6.32ab 6.53b0.20610.0223Ammonia N(mg/100ml)8.007.827.487.580.61260.9983Cecal VFA concentrationTotal(mmol/100ml)7.50a7.42a 6.73ab 5.57c0.6078<0.0001Acetic(mmol/100ml) 5.71a 5.63a 5.08a 4.34b0.64890.0007Propionic(mmol/100ml)0.410.450.440.490.16440.8431Butyric(mmol/100ml) 1.41a 1.34a 1.20ab0.14b0.17500.0185Cecal VFA proportionsAcetic(%)75.6075.6175.3872.72 3.29110.2899Propionic(%) 5.59 6.11 6.528.23 2.49830.2290Butyric(%)18.8118.2818.1019.05 2.76420.9041Acetic/(propionic+butyric) 3.14 3.20 3.09 2.710.48030.2298RMSE=root mean square error;VFA=volatile fatty acid.a,b Within a row,means without a common superscript letter differ(P<0.05).Effect of oat hulls for rabbit971García et al.,2002b).Moreover,insolubleﬁber and the less ligniﬁedﬁber fractions can act as substrate for micro-organisms and stimulate cecal fermentation and microbial nitrogen recycling(Gidenne et al.,2004;Gómez-Conde et al.,2009);thus they can affect and regulate the digestive health and growth performance of rabbits(Gidenne et al., 2010a and2010b).In the present study,we observed a higher feed intake in rabbits fed the150g/kg OH diet compared with diets with lower OH concentrations,probably associated with the lower digestible energy of the OH diet(Partridge et al.,1989;Nicodemus et al.,1999).FCR and ADG were similar to that described by María et al. (2007),using diets containing79g/kg OH in rabbits. According to García et al.(2002b)dietary inclusion of ﬁbrous feedstuffs at levels of100to150g/kg has little effect on rabbit performance,when the rabbit is able to regulate its digestible energy intake and thus to adjust its growth.The effect of dietary oat hulls levels on gastrointestinal tract developmentThe level and type of dietaryﬁber can play the most impor-tant role in controlling gastrointestinal tract development and digestive content(Margüenda et al.,2012).In the present study,no differences were observed in gastro-intestinal tract development among different treatments.The relative weights of each gastrointestinal tract were similar to those previously reported in healthy rabbits(Tao and Li, 2006;Chao et al.,2008).However,the relative weight of the full cecum decreased and the ceacal content was lower in rabbits fed the150g/kg OH diet compared with diets with lower OH concentrations,probably because of the lower level of neutral detergent solubleﬁber in OH.María et al.(2007) found that weight of cecal contents decreased linearly between rabbits fed beet pulp/apple pulp and OH diets,due to neutral detergent solubleﬁber reduction.Furthermore,in diets with the same level of dietaryﬁber,the type ofﬁber alters the time of fermentation in the cecum.Rice hulls is considered a kind of small particle size(<0.315mm)source ofﬁber,which might causes accumulation of digesta in the cecum(Fraga et al.,1991;Gidenne et al.,1992).However,no similar effect was observed in OH.These effects might account for the increase observed in feed intake.It would be partly related to the decrease of dietary digestible energy content when OH increased,and the negative effect of an accumulation of digesta in the cecum on feed intake(García et al.,2002a)obtained previously when the effects of54 diets were reviewed.The effect of dietary oat hulls levels on coefﬁcient of total tract apparent digestibility of nutrientsIn our study,the CTTAD of NDF and GE decreased with the inclusion of OH.Similar results have been reported pre-viously,using diets with79g/kg OH in rabbits(María et al., 2007).The CTTAD of NDF was lower in rabbits fed the 100g/kg and150g/kg OH diet,probably associated with the higher lignin and lower pectin content of this diet(Gidenne and Perez,1994;de Blas et al.,1999;Nicodemus et al., 1999).Besides,the higher feed intake and lower ceacal content weight in rabbits fed the150g/kg OH diet in this experiment assure a short cecal fermentation time and obviously a high degree of ligniﬁcation of NDF,which also would account for the relatively low efﬁciency of NDF digestion of OH.This is in agreement with previous studies(DePeters et al.,1997;Hall et al.,1998;Escalona et al.,1999)with ruminants,which have shown that the extent of NDF degradation is very high after72h of fermentation(94%),but also that the degradation rate of its potentially degradable NDF fraction(99.9%)is relatively low(0.038/h).Moreover,the CTTAD of GE was lower in rabbits fed the150g/kg OH diet than in rabbits fed the other diets,probably because of the lower neutral detergent solubleﬁber content of this diet.María et al.(2007)observed a linear increase of energy digestibility with neutral detergent solubleﬁber level.This result is in accordance with the lower CTTAD of NDF.The effect of dietary oat hulls levels on cecum fermentation In the present trial,the concentration of ammonia N in the cecal content was not affected by diet.This might be due toTable6The effect of oat hulls(OH)concentration on the carcass traits and meat quality of experimental rabbitsOH(g/kg)Items050100150RMSE P-value Hot carcass weight(g)12621214132012880.09500.1733 Dressing percentage(%)50.05a51.66a52.42a55.68b 5.08040.0481 pH(45min) 6.64 6.60 6.52 6.690.29700.7059 pH(24h) 5.91 5.81 5.75 5.750.26690.6232 L36.3036.3838.3938.14 2.62970.1857 a12.6112.7012.6412.660.32750.9571b 5.15 5.14 5.24 5.06 1.5990.9971Shear force12.4112.4612.4912.160.69320.7751 Cooking loss(%)25.5325.5225.6025.500.5530.9391 RMSE=root mean square error;L=lightness;a=redness;b=yellowness.a,b Within a row,means without a common superscript letter differ(P<0.05).Liangzhan,Xiang,Caixia,Zhaohui and Fuchang972the nearly same level of CP in these diets.Castellini et al. (2007)observed that a reduction of CP in the rabbit diet reduces the ammonia concentration in the cecum.The concentrations of total VFA observed in our study ranged from5.57to7.50mmol/100ml.In general,these values are consistent with those obtained by García et al. (2002a)and Pinheiro et al.(2009).Of note,in the present work,the production of total VFAs,acetic and butyric decreased with increase of OH concentration.These results were in agreement with Gidenne et al.(2000)who observed a linear decrease in cecal VFA level with increasing dietary ﬁber supply.Furthermore,at the same concentration of dietaryﬁber,the dietary inclusion of soluble and fermentableﬁber decreases the pH and increases the total cecal con-centration of VFA and the total mean retention time(García et al.,1993;Carabaño et al.,1997).We thus hypothesize that OH has a lower level of soluble and/or fermentableﬁber than RHM.VFA provide an important source of energy for the rabbit (Bellier and Gidenne,1996).Moreover,VFA,mainly butyrate, having anti-inﬂammatory action(Chiang et al.,2000;Qiao et al.,2002).Thus,negative effect may be observed with the increasing of OH,though not founded in the present study.The effect of dietary oat hulls levels on carcass traits and meat qualitiesSomeﬁber sources,such as sugar beet pulp(García et al., 1993;Cobos et al.,1995;Margüenda et al.,2012),olive pomaces(Dal Bosco et al.,2012),were tested at different levels of inclusion.All these studies found that the lower levels(5%to15%)of supplementation showed little or no effects on carcass traits,dressing percentage,meat chemical composition or physical characteristics such as tenderness, drip loss and color.These results are congruous with those obtained by our research.Increasing dietary concentration of OH did not affect hot carcass weight and dressing percentage and the pH(45min,24h),lightness,redness,yellowness, 24-h drip loss of LL muscles.However,in this study,the dressing percentage affected by the inclusion of OH.We found that dressing out percentage increased with higher (150g/kg)inclusion of OH.This effect is in accordance with the decrease of relative weight of the full cecum decreased and the ceacal content.A similar result that accumulation of digesta in the cecum lead to a reduction of dressing out percentage was observed by Carabaño et al.(1997)ConclusionsIn conclusion,the use of150g/kg OH in substitution for RHM could reduce the CTTAD of GE and NDF and impaired fermentation of the cecum content:the pH values increased and the VFA values decreased.OH could thus be considered as aﬁber source which has a lower level of soluble and/or fermentableﬁber for the fattening rabbit.Moreover,OH has a lower digestible energy which lead to a higher feed intake. However,OH can be included in rabbit diets at levels up to100g/kg almost without adverse effects on the growth performance,CTTAD of nutrients,gastrointestinal tract development,cecum fermentation and carcass traits.AcknowledgmentThis study was supported by the Special Fund for Agro-scientiﬁc Research in the Public Interest(2000903006)and by the ear-marked fund for Modern Agro-industry Technology Research System(CARS-44-B-1).ReferencesAssociation of Ofﬁcial Analytical Chemist(AOAC)1995.Ofﬁcial methods of analysis,15th edition.AOAC,Washington,DC,USA.Bellier R and Gidenne T1996.Consequence of reducedﬁbre intake on digestion, rate of passage and caecal microbial activity in the young rabbit.British Journal of Nutrition75,353–363.Carabaño R,García J and de Blas JC2001.Effect ofﬁber source on ileal apparent digestibility of non-starch polysaccharides in rabbits.Animal Science Journal72, 343–350.Carabaño R,Motta Ferreira W,de Blas JC and Fraga MJ1997.Substitution of sugarbeet pulp for alfalfa hay in diets for growing rabbits.Animal Feed Science and Technology65,249–256.Castellini C,Cardinali R,Rebollar PG,Dal Bosco A,Jimeno V and Cossu ME 2007.Feeding fresh chicory(Chicoria intybus)to young rabbits:performance, development of gastro-intestinal tract and immune functions of appendix and Peyer’s patch.Animal Feed Science and Technology134,56–65.Chao HY and Li FC2008.Effect of level ofﬁber on performance and digestion traits in growing rabbits.Animal Feed Science and Technology144,279–291. 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Annales De Zootechnie48,3–13.de Blas JC and Mateos GG1998.Feed formulation.In The nutrition of rabbit (ed.C de Blas and J Wiseman),pp.241–253.CABI Publishing,New York,NY,USA. DePeters EJ,Fadel JG and Arosamena A1997.Digestion kinetics of neutral detergentﬁber and chemical composition within selected by-product feedstuffs. Animal Feed Science Technology67,127–140.Escalona B,Rocha R,García J,Carabaño R and De Blas JC1999.Characteriza-tion of in situﬁbre digestion of severalﬁbrous feedstuffs.Animal Science Journal 68,217–221.Food and Agriculture Organization2011.FAOSTAT.Food and Agriculture Organization of the United Nations,Rome,Italy.Fraga MJ,Pérez de Ayala P,Carabaño R and De Blas JC1991.Effect of type of ﬁber on the rate of passage and on the contribution of soft feces to nutrient intake ofﬁnishing rabbits.Journal of Animal Science69,1566–1574.Fraser J and McCartney D2004.Fodder oats in North America:chapter III.In Fodder oats:a world overview.FAO plant production and protection series NO°33(ed.JM Suttie and SG Reynolds),251pp.FAO,Rome,Italy.García G,Galvez JF and de Blas JC1993.Effect of substitution of sugar beet pulp for barley in diets forﬁnishing rabbits on growth performance and on energy and nitrogen efﬁciency.Journal of Animal Science711,823–1830.Effect of oat hulls for rabbit973。

The role of interfaces in fiber-reinforced brittle matrix composites

NOMENCLATURE Matrix flaw radius Debond length Matrix crack spacing Longitudinal modulus of composites, f E1 + (1 -- f ) E m E, Young's modulus of fiber Young's modulus of matrix Fiber volume fraction f Energy release rate at crack tip hFiber pull-out length Roughness amplitude H J integral J 3 Composites Scienceand Technology 0266-3538/91/$03.50© 1991ElsevierSciencePublishers Ltd, England. Printed in Great Britain a d D E
1 INTRODUCTION Interfaces have a dominant effect on the mechanical properties of brittle matrix composites, such as fiber-reinforced ceramics, glasses and intermetallics. Generally, for enhanced crack growth resistance, the interface between the fiber and the matrix must be 'weak'. Indeed, 'weak' interfaces are a prerequisite for attainment of fracture resistances that appreciably exceed those of the matrix, whereupon frictional dissipation along the debonded interfaces becomes the primary source of enhanced 'toughness'. Conversely, creep resistance is enhanced by having a 'strong' interface. Consequently, a rigorous definition of 'weak' and 'strong' needs to be established for interfaces of interest. Thermoehemical and thermomechanical consider-

Fatigue strength of steel fibre reinforced concrete in flexure

Fatigue strength of steel ﬁbre reinforced concrete in ﬂexureS.P.Singha,*,S.K.KaushikbaDepartment of Civil Engineering,Regional Engineering College,Jalandhar 144011,India bDepartment of Civil Engineering,University of Roorkee,Roorkee 247667,IndiaReceived 2March 2000;accepted 2September 2002AbstractThe paper presents a study on the fatigue strength of steel ﬁbre reinforced concrete (SFRC).An experimental programme was conducted to obtain the fatigue-lives of SFRC at various stress levels and stress ratios.Sixty seven SFRC beam specimens of size 500Â100Â100mm were tested under four-point ﬂexural fatigue loading.Fifty four static ﬂexural tests were also conducted to determine the static ﬂexural strength of SFRC prior to fatigue testing.The specimens incorporated 1.5%volume fraction of cor-rugated steel ﬁbres of size 0:6Â2:0Â30mm.Concept of equivalent fatigue-life,reported for plain concrete in literature,is applied to SFRC to incorporate the eﬀects of stress level S ,stress ratio R and survival probability L R into the fatigue equation.The results indicate that the statistical distribution of equivalent fatigue-life of SFRC is in agreement with the two-parameter Weibull distri-bution.The coeﬃcients of the fatigue equation have been determined corresponding to diﬀerent survival probabilities so as to predict the ﬂexural fatigue strength of SFRC for the desired level of survival probability.Ó2002Elsevier Ltd.All rights reserved.Keywords:Fatigue;Equivalent fatigue-life;Steel ﬁbre reinforced concrete;Stress level;Stress ratio;Flexure1.IntroductionConsiderable interest has developed in the fatigue strength of concrete members in recent years.There are several reasons for this.Firstly,the use of high strength materials require that the concrete members perform satisfactorily under high stress levels.Hence,the study of the eﬀects of repeated loads on bridge slabs and crane beams is a matter of concern.Secondly,diﬀerent con-crete systems such as prestressed concrete railroad ties and continuously reinforced concrete pavement slabs are often used.The use of these systems demand a high performance product with an assured fatigue-life.Thirdly,there is a new recognition of the eﬀects of re-peated loading on a member,even if it does not cause a fatigue failure.There may be inclined cracks in the prestressed concrete beams at lower loads due to fatigue loading and the static load carrying capacity of the component material may be altered.Many researchers carried out laboratory fatigue ex-periments to investigate the fatigue behaviour of plain as well as steel ﬁbre reinforced concrete since Feret Õs pioneer tests [1].Oh,[16,21]studied the distribution of ﬂexural fatigue-life of plain concrete for various stress levels and found that it follows the two-parameter Weibull distribution.Following equations have been used in the past by the researchers to study the fatigue of concrete:S ¼a Àb log ðN Þð1ÞS ¼1Àb ð1ÀR Þlog ðN Þfor 06R 61ð2ÞS ¼C 1ðN ÞÀC 2ð3Þwhere a ,b ,C 1and C 2are experimental coeﬃcients.Many researchers [2,9,14]used Eq.(1)which represents the relationship between stress level S ,and number of cycles to failure N .Eq.(2)used by researchers [12–14,16]is a modiﬁed form of the Eq.(1)which takes into ac-count the eﬀect of minimum fatigue stress ðf min Þin the form of stress ratio R ,ðR ¼f min =f max Þ.Aas-Jakobsen [7]obtained the value of b in Eq.(2)equal to 0.064for compression fatigue of concrete.However,Tepfers et al.[12]recommended the value of b as 0.0685.Oh [16]*Corresponding author.Tel.:+91-181-293301x229;fax:+91-181-2991120.E-mail address:spsingh_recjal@ (S.P.Singh).0958-9465/$-see front matter Ó2002Elsevier Ltd.All rights reserved.doi:10.1016/S0958-9465(02)00102-6Cement &Concrete Composites 25(2003)779–786tested the Eq.(2)forﬂexural fatigue of plain concrete and obtained the value of b as0.0690.Eq.(3)relates the stress level S to the number of cycles for failure N by a power relation.It has been used by pavement re-searchers such as Vesic and Saxena[6].Shi et al.[22]introduced the concept of equivalent fatigue life(EN),in an attempt to incorporate the eﬀect of stress ratio and survival probability into the Eq.(3). They modiﬁed the Eq.(3)by replacing N with EN to get a new equation as follows:S¼C1ðENÞÀC2ð4ÞThe coeﬃcients C1and C2of Eq.(4)were obtained for plain concrete for diﬀerent survival probabilities.It is also shown that the statistical description of equivalent fatigue-life follows the two-parameter Weibull distribu-tion[22].The studies on steelﬁbre reinforced concrete(SFRC) were mainly conﬁned to the determination of itsﬂexural fatigue endurance limit for diﬀerent type/volume frac-tion/aspect ratio ofﬁbres[10,17–20].Yin and Hsu[23] studied the fatigue behaviour of steelﬁbre reinforced concrete under uniaxial and biaxial compression and observed that the S–N curves can be approximated by two straight lines connected by a curved knee instead ofa single straight line.2.Research signiﬁcanceThe work of Shi et al.[22]provides a good oppor-tunity to apply the concept of equivalent fatigue-life to the data of steelﬁbre reinforced concrete subjected toﬂexural fatigue loading and to examine the two-parameter Weibull distribution to describe the distri-bution of equivalent fatigue-life of SFRC.It is also proposed to obtain the coeﬃcients of the fatigue equa-tion(4)corresponding to diﬀerent reliabilities/survival probabilities,making the equation thus applicable to SFRC.3.Experimental programmeThe concrete mix used for casting the test specimens is shown in Table1.Ordinary Portland Cement,crushed stone coarse aggregates(maximum size12mm)and Badarpur sand were used.The materials used con-formed to relevant Indian Standard speciﬁcations. Corrugated steelﬁbres of size30Â2:0Â0:6mm at1.5% volume fraction were incorporated in the concrete.The specimens used forﬂexural fatigue tests as well as static ﬂexure tests wereﬁbre concrete beams of size100Â100Â500mm.The specimens were cast in14batches, each batch consisting of nine standardﬂexural test specimens and four150Â150Â150mm cubes.The cube specimens were used to determine the28days compressive strength for each batch.The mixing was done in a rotary mixer and theﬁbres were gradually sprinkled into the drum by hand.The specimens were cured for60days to avoid a possible strength increase during fatigue tests.The specimens were removed from the curing bath and kept in the laboratory conditions till testing.The28days average compressive strength of the mix was46.34MPa.Four beams from each batch were tested in a100kN INSTRON closed loop universal testing machine to determine the mean staticﬂexural strengthðf rÞ.The beams were simply supported on a span of450mm and loaded at third points.The average staticﬂexural strength of the mix was8.76MPa.The fatigue tests were conducted on a100kN MTS closed loop electrohy-draulic universal testing machine.The span/points of loading in the fatigue tests were kept the same as for the statictests. Table1Mixture proportionWater/cement ratio Sand/cement ratio Coarse aggregate/cementratio0.46 1.52 1.88 780S.P.Singh,S.K.Kaushik/Cement&Concrete Composites25(2003)779–786Flexural fatigue tests were conducted at diﬀerent stress levelsÔSÕ(S¼f max=f r;f max¼maximum fatigue stress,f r¼static flexural stress),ranging from0.90to0.60and at two diﬀerent stress ratiosÔRÕ(R¼f min=f max;f min¼minimum fatigue stress)i.e.0.10,and0.30. Constant-amplitude sinusoidal loads were applied at a frequency of12Hz.The number of cycles to failure for each specimen under diﬀerent load conditions were no-ted as fatigue-life N.With the decrease in the stress level, the number of cycles to failure of the specimens went on increasing.Since fatigue testing is a very time consuming and expensive process,an upper limit of the number of cycles i.e.2million cycles,to be applied was selected. The test was terminated as and when the failure of the specimen occurred or this upper limit was reached whichever was earlier.4.Analysis of the fatigue test dataThe results of the fatigue tests as obtained in this investigation are given in rge variability was observed in the fatigue-life data,particularly at stress level at stress levels0.80,0.75,0.70and0.65.It was diﬃcult to carry out analysis of the data in such a case. This diﬃculty was resolved by merging the original data at stress levels0.80and0.75;and0.70and0.65into two groups and using the average value of the stress levelsi.e.0.775(average of stress levels0.80and0.75)and0.675(average of stress levels0.70and0.65)for each group in the analysis of the data.Some data points in Table2may be treated as out-liers.ChauvenetÕs criterion[11]was applied to data points at each stress level and points meeting this cri-terion were excluded from further analysis.To carry out the analysis when both stress level S and stress ratio R are variables,concept of equivalent fa-tigue-life was introduced by Shi et al.[22].They deﬁned equivalent fatigue-life as follows:EN¼ðNÞ1ÀRð5ÞEq.(5)was obtained from Eqs.(1)and(2).The fa-tigue-life data as given in Table2has both S and R as variables.It is diﬃcult to carry out the statistical anal-ysis in such a case.Shi et al.[22]observed that‘‘all the fatigue-life data at a certain stress level S with diﬀerent R values can be transformed to have a common equivalent fatigue-life EN by applying Eq.(5).The analysis of the fatigue-life N with two variables S and R now becomes an analysis of the equivalent fatigue-life EN with one variable S’’.Equivalent fatigue-lives for SFRC at dif-ferent stress level as obtained by Eq.(5)are summarised in Table3.Table2Laboratory fatigue-life data(number of cycles to failure,N,in as-cending order)for steelﬁbrous concreteðV f¼1:5%ÞStress ratioÔRÕStress levelÔSÕ0.900.850.775a0.675a0.600.102426437b1706b124,390c50300574247,2682,000,000d62300736051,68078350830065,960100384916081,9103312b51613,104132,86056414,420189,820120016,960206,880124023,316280,910145235,260375,540156051,120585,750232875,900920,160258090,5401,238,370315047,364b0.30212308b272b368608080,9604309600100,14081010,276156,760128032,796313,68016,200b45.580550,400a Obtained by merging data at stress levels0.80and0.75,0.70and0.65,respectively.b Rejected as outliers by ChauvenetÕs criterion,not included in analysis.c As the specimen failed at a low number of cycles,hence rejected.d Specimen did not show any cracks,test terminated at2Â106 cycles,treated as run out,not included in analysis.Table3Equivalent fatigue-life data(EN,in ascending order)for SFRC, (V f¼1:5%)Stress levelÔSÕ0.900.850.7750.675 17151241616,111 34170272717,45841170302121,745 43195316526,424 50212336640,837 63276367956,300 63299433260,834 70445507880,114 1095915534104,038 1506086404155,2186137039233,0656438529304,48570110,43474812,375107217,287117624,673140828,91714491824S.P.Singh,S.K.Kaushik/Cement&Concrete Composites25(2003)779–7867814.1.Graphical method of analysisA number of mathematical probability models have been employed for the statistical description of fatigue data.One of the popular models has been the logarith-mic-normal (lognormal)distribution function [4].How-ever,it was pointed out by Gumble [5]that the hazard function or risk function for lognormal distribution de-creases with increasing life.The Weibull distribution has an increasing hazard function with time and is most commonly used for describing the fatigue data these days.The survivorship function of the two-parameter Weibull distribution can be written as follows [3,8,16,22]:L R ðn Þ¼exp h Àn ua ið6Þin which n ¼specific value of the random variable;a ¼shape parameter or Weibull slope at stress level S ;u ¼scale parameter or characteristic life at stress level S .Taking the logarithm twice of both sides of Eq.(6):ln ln 1L R !¼a ln ðn ÞÀa ln ðu Þð7ÞThis equation can be used to verify whether the sta-tistical distribution of equivalent fatigue-life of SFRC,at a given stress level S ,follows the two-parameter Weibull distribution.The equivalent fatigue-life data at a given stress level must be ﬁrst arranged in ascending order to obtain a graph from Eq.(9)and the empirical survivorship function can be calculated from the fol-lowing relation [8,11,16,21]:L R ¼1Ài ð8Þin which i ¼failure order number and k ¼number of equivalent fatigue data or sample size at a givenstress782S.P.Singh,S.K.Kaushik /Cement &Concrete Composites 25(2003)779–786level S .A graph is plotted between ln ½ln ð1=L R Þ and ln ðEN Þ,and if a linear trend is observed for the equi-valent fatigue-life data at a given stress level S ,it can be assumed that the two-parameter Weibull distribution is a reasonable assumption for the statistical description of equivalent fatigue-life data at that stress level.The pa-rameter a and u can be directly obtained from the graph.Fig.1shows the plots of the equivalent fatigue-life data at S ¼0:90,0.85,0.775and 0.675.It can be ob-served that the data points fall approximately along a straight line,which indicates that the two-parameter Weibull distribution is a reasonable assumption for the distribution equivalent-fatigue-life of SFRC at these stress levels.The corresponding values of the correlation coeﬃcient (C C )are 0.974,0.964,0.927and 0.962,re-spectively as shown in Fig.1.Table 4presents the basic calculations to plot the equivalent fatigue-life data of SFRC at stress level S ¼0:90.The estimated parameters for the equivalent fatigue-life data of SFRC,at diﬀerent stress levels are shown in Fig.1and Table 5.4.2.Parameters from the method of momentsThe parameters of the Weibull distribution for the equivalent fatigue-life of SFRC at a given stress level can also be obtained by the method of moments using the following relations [8,15,16,21]:a ¼ðCV ÞÀ1:08ð9Þu can be estimated from the following equationu ¼lT 1þ1ÀÁð10Þwhere l is the sample mean of the data at a given stress level and CV the coeﬃcient of variation of the data,T ðÞis the gamma function.The equivalent fatigue-life data given in Table 3has been analysed to obtain the distribution parameters by this method.The calculated parameters are listed in Table 5.4.3.Parameters from the method of maximum likelihood estimateThe method of maximum likelihood estimate was also used for calculation of distribution parameters of the Weibull distribution for the equivalent fatigue-life data of SFRC at various stress levels [8,21].The values of the parameters i.e.shape parameter and characteristic extreme life as estimated by this method are listed in Table 5.It can be seen from Table 5that all the three methods employed here to estimate the parameters of the Weibull distribution yield almost similar results except for the equivalent fatigue-life data at stress level S ¼0:775where the value of the shape parameter a obtained by the method of moments is much diﬀerent from the one obtained by the other two methods.Hence,in this case,the average values of the parameters obtained by the graphical method and by the method of maximum likelihood estimate are used for further analysis.Table 4Equivalent fatigue-lives and empirical survivorship function for S ¼0:90i EN iL R ¼1Àik þ1ln ½ln ð1=L R Þ ln ðEN i Þ1170.9091)2.3507 2.83322340.8182)1.6062 3.52643410.7273)1.1444 3.71364430.6364)0.7942 3.76125500.5455)0.5008 3.91206630.4545)0.2376 4.14317630.3636þ0.0116 4.14318700.2727þ0.2619 4.248591090.1818þ0.5335 4.6913101500.0909þ0.87465.0106Table 5Values of the Weibull parameters for equivalent fatigue-life,SFRC (V f ¼1:5%)S ¼0:90S ¼0:85S ¼0:775S ¼0:675au a u a u a u Graphical method 1.602171 1.2994754 1.285796430.994099,154Method of moments1.704370 1.3791735 1.12009112 1.002993,052Method of maximum likelihood 1.716971 1.3892736 1.32989694 1.076995,902Average1.6744711.35597411.3078a9669a1.024696,036aAverage of the values of the parameters obtained by the graphical method and the method of maximum likelihood estimate.Table 6Calculated equivalent fatigue-lives corresponding to diﬀerent reliabil-ities L R S ¼0:90S ¼0:85S ¼0:775S ¼0:6750.95128399852900.9019141173010,6800.802924530122,2150.7038346439635,1120.6048452578549,8550.5057565730667,155S.P.Singh,S.K.Kaushik /Cement &Concrete Composites 25(2003)779–7867835.Goodness-of-ﬁt testsIt has been shown in the preceding sections that the equivalent fatigue-life data of SFRC at a given stress level S ,can be modelled by the two-parameter Weibull distribution.To further substantiate this,the v 2-test and Kolmogorov–Smirnov test as described by Oh [21]were carried out on the equivalent fatigue-life data of SFRC at each stress level.These tests indicate that the two-parameter Weibull distribution is a valid model for the statistical distribution of equivalent fatigue-life of SFRC at 5%level ofsigniﬁcance.784S.P.Singh,S.K.Kaushik /Cement &Concrete Composites 25(2003)779–7866.Coeﬃcients of the fatigue equation for SFRCIt has been shown in the preceding sections that the equivalent fatigue life data of SFRC can be described by the two-parameter Weibull distribution.Therefore,it can be used to calculate the equivalent fatigue-lives corresponding to diﬀerent survival ing the average values of the parameters as obtained above by diﬀerent methods,the calculated values of the equivalent fatigue-lives are listed in Table6.The coeﬃcients C1and C2of the Eq.(4)can be ob-tained by regressing it against the data in Table6.Taking logs on both sides of the Eq.(4)logðSÞ¼logðC1ÞÀC2x logðENÞð11ÞFig.2shows the results of the regression analysis.The coeﬃcients thus obtained are listed in Fig.2and Table 7.These coeﬃcients can be chosen for the desired level of the survival probability.Eq.(4)can be written in the following form:S¼C1ðNÞÀC2ð1ÀRÞð12ÞThe Eq.(12)can thus be used by the design engineers to estimate theﬂexural fatigue strength of SFRC for the desired level of survival probability.The results obtained are obviously applicable for SFRC with1.5%ﬁbre content and the type and the aspect ratio of theﬁbres used.The authors also tested SFRC with1.0%and0.5%ﬁbre content.The results were analysed and it was observed that same general conclusions could be drawn as for as the parameters of the Weibull distribution and the coeﬃcients of the fa-tigue equation are concerned.However,additional re-search work is required to be carried out to investigate as to how theﬁbre type and aspect ratio aﬀect the pa-rameters of the Weibull distribution and the coeﬃcients of the fatigue equation.7.ConclusionThe concept of equivalent fatigue-life as reported in literature,has been applied to SFRC.It has been shown that the statistical distribution of equivalent fatigue-life of steelﬁbre reinforced concrete at a given stress level,S approximately follows the two-parameter Weibull dis-tribution.The parameters of the Weibull distribution for the equivalent fatigue-life are obtained by the graphical method,the method of moments and the method of maximum likelihood estimate.The coeﬃcients of the fatigue equation have been determined for SFRC cor-responding to diﬀerent survival probabilities,thus in-corporating the survival probabilities into the fatigue equation.The fatigue equation can be used for obtain-ing theﬂexural fatigue strength of steelﬁbre reinforced concrete for the desired level of survival probability. However,additional work is needed to determine as to how theﬁbre type and aspect ratio aﬀect the results i.e.the parameters of the Weibull distribution and the coeﬃcients of the fatigue equation. AcknowledgementsTheﬁnancial assistance received from the Council of Scientiﬁc&Industrial Research(CSIR),New Delhi to carry out the reported research investigation is gratefully acknowledged.References[1]Feret R.Etude experimentale du ciment arme.Grauthier-Villiers;1906.[chapter3].[2]Kesler CE.Eﬀect of speed of testing onﬂexural strength of plainconcrete.In:HRB Proceedings,vol.32.p.1953.[3]Weibull W.Fatigue testing and analysis of results.Oxford:Pergamon Press;1961.[4]ASTM.A guide for fatigue testing and the statistical analysis offatigue data.ASTM Spec Tech Publ1963;91-A.[5]Gumble EJ.Parameters in the distribution of fatigue life.J EngMech,ASCE1963;(October).[6]Vesic AS,Saxena SK.Analysis of structural behaviour of roadtest rigid pavements.Highway Research Record,no.291,1969.[7]Aas-Jakobsen K.Fatigue of concrete beams and columns.BulletinNo.70-1,NTH Institute for Betonkonstruksjoner,Trondheim, September,1970.[8]Wirsching PH,Yao JTP.Statistical methods in structural fatigue.J Struct Div,Proc ASCE1970;(June).[9]Ballinger CA.Cumulative fatigue damage characteristics of plainconcrete.Highway Research Record,no.370,1972.[10]Batson G,Ball C,Bailey L,Lenders E,Hooks J.Flexural fatiguestrength of steelﬁbre reinforced concrete beams.ACI J1972;(November).[11]Kennedy JB,Neville AM.Basic statistical methods for engineersand scientists.New York:A Dun-Donnelley Publishers;1976. [12]Tepfers R,Kutti T.Fatigue strength of plain,ordinary,and lightweight concrete.ACI J1979;(May).[13]Tepfers R.Tensile fatigue strength of plain concrete.ACI J1979;(August).[14]Hsu TTC.Fatigue of plain concrete.ACI J1981;(July–August).[15]Wirsching PH,Yao JTP.Fatigue reliability-introduction.J StructDiv,Proc ASCE1982;(January).[16]Oh BH.Fatigue analysis of plain concrete inﬂexure.J Struct Eng1986;112(2).Table7Coeﬃcients C1and C2of the fatigue equation corresponding to dif-ferent reliabilitiesL R C1C20.95 1.02610.04550.90 1.04340.04410.80 1.05730.04230.70 1.06580.04130.60 1.07360.04070.50 1.07860.0401S.P.Singh,S.K.Kaushik/Cement&Concrete Composites25(2003)779–786785[17]Ramakrishnan V,Oberling G,Tatnall P.Flexural fatigue strengthof steelﬁbre reinforced concrete.ACI Spec Publ1987;SP-105-13.[18]Tatro SB.Performance of steelﬁbre reinforced concrete usinglarge aggregates.Transportation Research Record1110,TRB Washington,1987.[19]Ramakrishnan V,Wu GY,Hosalli G.Flexural fatigue strength,endurance limit and impact strength ofﬁbre reinforced con-cretes.Transportation Research Record1226,TRB,Washington, 1989.[20]Johnston CD,Zemp RW.Flexural fatigue performance of steelﬁbre reinforced concrete-inﬂuence ofﬁbre content,aspect ratio and type.ACI Mater J1991;(July–August).[21]Oh BH.Fatigue-life distributions of concrete for various stresslevels.ACI Mater J1991;(March–April).[22]Shi XP,Fwa TF,Tan SA.Flexural fatigue strength of plainconcrete.ACI Mater J1993;2(September–October).[23]Yin W,Hsu TTC.Fatigue behaviour of steelﬁbre reinforcedconcrete in uniaxial and biaxial compression.ACI Mater J 1995;(January–February).786S.P.Singh,S.K.Kaushik/Cement&Concrete Composites25(2003)779–786。

Bamboo fibre reinforced biocomposites A review

ReviewBamboo ﬁbre reinforced biocomposites:A reviewH.P.S.Abdul Khalil a ,⇑,I.U.H.Bhat a ,M.Jawaid b ,A.Zaidon c ,D.Hermawan d ,Y.S.Hadi daSchool of Industrial Technology,Universiti Sains Malaysia,11800Penang,MalaysiabDepartment of Polymer Engineering,Faculty of Chemical Engineering,Universiti Teknologi Malaysia,81310UTM Skudai,Johor,Malaysia cFaculty of Forestry,Universiti Putra Malaysia,43400Serdang,Selangor,Malaysia dDepartment of Forest Product,Faculty of Forestry,Kampus IPB,Darmaga,Bogor Agricultural University,Bogor 16001,West Java,Indonesiaa r t i c l e i n f o Article history:Received 11May 2012Accepted 9June 2012Available online 19June 2012Keywords:Bamboo ﬁbres BiocompositesMechanical properties Thermal propertiesa b s t r a c tThe reduction in harmful destruction of ecosystem and to produce low cost polymeric reinforced com-posites,the researchers are emerging with policies of manufacturing the composites using natural ﬁbres which are entirely biodegradable.These policies had generated safe strategies to protect our environ-ment.The utilization of bamboo ﬁbres as reinforcement in composite materials has increased tremen-dously and has undergone high-tech revolution in recent years as a response to the increasing demand for developing biodegradable,sustainable,and recyclable materials.The amalgamation of matrix and nat-ural ﬁbres yield composite possessing best properties of each component.Various matrices used cur-rently are soft and ﬂexible in comparison to natural ﬁbres their combination leads to composite formation with high strength-to-weight ratios.The rapid advancement of the technology for making industry products contributes consumer the ease of making a suitable choice and own desirable tastes.Researchers have expanded their expertise in the product design by applying the usage of raw materials like bamboo ﬁbre which is stronger as well as can be utilized in generating high end quality sustainable industrial products.Thereby,this article gives critical review of the most recent developments of bamboo ﬁbre based reinforced composites and the summary of main results presented in literature,focusing on the processing methodology and ultimate properties of bamboo ﬁbres with polymeric matrices and applications in well designed economical products.Ó2012Elsevier Ltd.All rights reserved.1.IntroductionThe soaring prices of raw materials for engineering and standard plastics,the future sustainability of natural reservoirs and threat to environment have forced to use natural redeemable materials for development and fabrication of polymer composites [1,2].The use of synthetic ﬁbres had dominated the recent past of reinforcement industry;however the natural ﬁbre reinforcement had gained much impetus to substitute this synthetic ﬁbre in various applica-tions [3].The combination of natural ﬁbres with polymer matrices from both non renewal (petroleum based)and renewal resources used to produce polymer composites that are competitive with synthetic composites is gaining attention over the last decade [4].Biodegradable plastics and bio-based polymer products from re-newal resources can form sustainable and eco-friendly products than can compete and capture current market which is dominated by petroleum based products [5].Researchers have exploited both softwoods as well as hardwoods to extract the ﬁbres for reinforce-ment in various composites [3].For some developing countries,natural ﬁbres are of vital economic importance:for example,cotton in some West African countries,jute in Bangladesh and sisal in Tanzania [1].The countries where there is scarcity of forest resources,agri-cultural crops have been utilized for developments and research on polymer composites.Bamboo is one of the agricultural crops which can be exploited for the design and development of polymer composites [6].Bamboo is found in abundance in Asia and South America.In many Asian countries bamboo has not been explored fully to its extent although it is considered as natural engineering material.This sustainable material has evolved as backbone for socio-economical status of society as it takes several months to grow up.Traditionally bamboo has been used in various living facility and tools,which owes to its high strength to its weight.This property is due to the longitudinal alignment of ﬁbres.In practice,it is mandatory to fabricate the bamboo based composites in addi-tion to the extraction of bamboo ﬁbres in controlled way from bamboo trees [7,8].The bamboo ﬁbres are naturally possessed with ﬁner mechanical properties,but are brittle in nature as com-pared to other natural ﬁbres due to the extra lignin content cover-ing the bamboo ﬁbres.Presently bamboo is considered important plant ﬁbre and has a great potential to be used in polymer composite industry.Its0261-3069/$-see front matter Ó2012Elsevier Ltd.All rights reserved./10.1016/j.matdes.2012.06.015Corresponding author.Tel.:+6046532200;fax:+604657367.E-mail addresses:akhalilhps@ ,akhalil@usm.my (H.P.S.Abdul Khalil).structural variation,mechanical properties,extraction ofﬁbres, chemical modiﬁcation,and thermal properties had made it versa-tile for the use in composite industry[9,10].On the basis of earlier reports,bamboo has60%cellulose with high content of lignin and its microﬁbrillar angle is2–10°,which is relatively small.This char-acteristic property has made bambooﬁbre asﬁbre for reinforce-ment in variety of matrices[9,11].A variety of methods have been developed by researchers to extract the bambooﬁbre for reinforcement of composites.Alkaline treatment was used as a tool for facilitation of bambooﬁbre extraction and optimizes separation of bambooﬁbres for preparation of bambooﬁbre reinforced poly-mer composites[12,13].Researchers investigated the changes occurring inﬁne structure of bambooﬁbre due to treatment with different concentration of alkali solution[14].In an interesting study,researchers investigated effect of mercerization of bamboo ﬁbres on mechanical and dynamical mechanical properties of bam-boo composites[15,16].The common approach towards fabrica-tion of composites from bamboo is to obtain better properties as compared to syntheticﬁbres.Bambooﬁbres used asﬁller and twin-screw extruder was used for compounding of bamboo and biodegradable polymer for fabrication of bamboo reinforced poly-mer composites[9].In another study,researchers used orthogonal bambooﬁbre strip mats for fabrication of bambooﬁbre reinforced epoxy and polyester composites by using hand lay-up technique [17,18].Dried bambooﬁbres were used for preparation of short bambooﬁbres reinforced epoxy composites and their chemical resistant and tensile properties withﬁbre length have been studied [19].Researchers used bamboo belongs to species of Bambusa Par-avariabilis,which grows abundantly in Asia for development of bambooﬁbre reinforced polypropylene composites[20].In an interesting study,bamboo which commonly grown in Singapore and can be abundantly throughout Southeast Asia was used to-gether with E-glassﬁbres as reinforcement in the hybrid compos-ites[21].Researchers studied the effect ofﬁbre length on the mechanical properties of polymer composites by using starch resin and short bambooﬁbres[22].A considerable effort has been made by researchers in good use of bambooﬁbre as reinforcement in polymer composites.Bamboo ﬁbres extracted from raw bamboo tress by steam explosion tech-nique used for development of eco-composites and evaluated mechanical properties of bambooﬁbre reinforced polymer com-posites[23].Biodegradable and environment-friendly green com-posites developed by utilizing micro/nano-sized bambooﬁbrils possessing moderate strength and stiffness[24].Flexural proper-ties of bio-based polymer composites made from bamboo and bio-degradable resin were evaluated and it compared with kenaf composites[25].They also calculatedﬂexural modulus by Cox’s model that incorporates the effect ofﬁbre compression were in good agreement with experimental results.Morphological and mechanical properties of bambooﬂourﬁlled HDPE based compos-ites were investigated in respect of crystalline nature of maleated elastomer modiﬁer,combined EPR-g-MA and PE-g-MA modiﬁer systems and loading rate of bambooﬂour in the presence of com-bined modiﬁer[26].Researchers investigated thermal properties of jute/bagasse hybrid composites and observed that thermal proper-ties of hybrid composites increased by increasing char residue at 600°C[27].Polypropylene/polylactic acid/bambooﬁbres blend composites were fabricated and morphological,and thermal prop-erties of blend composites compared with neat polymers[28].The presence of different functionalities particularly hydroxyl groups in the bambooﬁbres would lead to the weak interfacial bonding betweenﬁbres and the relatively hydrophobic polymers, therefore researchers have tried to improve these properties by dif-ferent interfacial treatments[29].The strengthening effects on the bambooﬁbres containing various matrices such as polystyrene, polyester and epoxy resins have been extensively studied.The eco-nomic value,light weight,high speciﬁc strength and non hazardous nature of bambooﬁbres are among most attractive properties of this material which makes researchers to work in the direction of composite technology.Therefore,it can be revealed that bambooﬁ-bre based composites have potential use in automotive industry, can replace the non-renewable,costly syntheticﬁbres in composite materials,particularly in the automotive industry and including household sectors.Presently an ecological threat has forced many countries to pass laws for using95%recyclable materials in vehi-cles.The current era is the time for using naturalﬁbres,particularly bambooﬁbre based composites in daily lives.The extensive re-search from everyﬁeld either engineering,biotechnological(genet-ic engineering),cultivation,etc.are trying to make one goal of utilizing these bambooﬁbres in better way in composite Industry.2.Socio-economic aspects of bamboo and bambooﬁbre reinforced compositesThe diversity of bamboo is itself reﬂected by its number of spe-cies,there are roughly1000species of bamboo found word wide. Bamboo grows very fast rather it is better to say extremely fast growing grass.Since,ancient time’s bamboo has been utilized in many Asian countries as well as South America for centuries. Bamboo can be considered an ecological viable substitute for com-monly used wood in many ways.Bamboo attains maturity in 3years as compared to wood which takes almost more than 20years.After maturity tensile strength of bamboo is comparable to mild steel.The growth rate of bamboo is unbelievable,the known fastest bamboo grows vertically two inches per hour and in some moso bamboo species the height of60feet is achieved only in 3months,thus the cutting down this substitute wood would not af-fect the ecological balance at all.Trade for bamboo and bamboo products is growing very rapidly,the reason for market value of bamboo is shortage of wood production in many countries and bamboo is best option to substitute wood in terms of growth factor [30].The business and trade of bamboo and its products either house hold materials,panels or decorating products has a collective effect on both global environment as well as economic develop-ment.Although the export trade of raw bamboo materials showed a decrease from US$61million in2001to US$45million in2009, the decrease in export of bamboo may be due to the domestic uti-lization of bamboo.The China is highest exporter to USA and EU (Table1).The farmers are primary beneﬁters for growing and harvesting the bamboo.The good source of income from growing and harvest-ing the bamboo has polished their basic skills in terms of cultiva-Table1Bamboo export and import tradeﬂow.Source:http://trade.inbar.int/Home/Analysis.Top exporters Top importersCountry US$million Country US$millionCanada3Turkey7South Africa3Norway8Mexico3India9Nigeria8Mexico9Hong Kong,China9South Africa12Malaysia14Hong Kong,China13Myanmar15Russia19Singapore18Switzerland20Thailand18Rep.of Korea25Philippines30Australia26USA30Singapore31EU-2754China40Vietnam84Canada54Indonesia269Japan194China1034USA254Eu-27230354H.P.S.Abdul Khalil et al./Materials and Design42(2012)353–368tion,handle the pressure if there is some loss in marketing of bam-boo,and enrich them with empowering ability.The ecological sys-tem is directly related to bamboo plantation,it helps in reducing landslides,soil erosion,and an unproductive land can be converted into productive land.The livelihood of poor rural farmers is boosted by bamboo cultivation skills.The protection of degraded land and environment can be well established by cultivating the bamboo,not only this food security can be evolved by intercrop-ping the bamboo with other food plants.The bamboo cultivation requires least investments;the investment is needed for bamboo propagation,land and manpower.The socio-economic beneﬁts in terms of raw materials cultivation or product development (Furni-ture,ﬂooring,bamboo based composites,fencing,decoration,etc.)leading to production of long lasting consumer goods is no doubt contributing to a greater extent in developing the economic values of many countries [30]The depletion of natural resources and fast increasing prices of crude oil have triggered the interest in utilizing the bamboo in composite technology.Imposing the strict laws to design the eco-friendly consumer goods is forcing industries to de-velop the methodology of using regenerable resources for fabrica-tion of composites;bamboo is one among the best resources which can be used as reinforcing agent in composites instead of using glass ﬁbres which directly depend on the depleting natural re-sources [31].The researchers are looking for the greener solution of this environmental threat.The easy availability of bamboo has stimulated a new era of composite industry.A step towards policy making and technological initiatives need to speed up to use bam-boo composites in public interest in order to avoid the use of wood.The evolution in bamboo based composites in house hold things,transportation,construction have moulded the bamboo economics into new direction while beneﬁting the common people both eco-nomically as well as socially.The promotion of bamboo based com-posites have generated new avenues for employment,all over world the policies are being made to develop interest among com-mon masses by implying different policies for example exempting bamboo composites from excise duties [32].3.Bamboo ﬁbres3.1.Global distribution of bambooThe bamboo is grown in various continents of the world,it has been divided accordingly;Asia–Paciﬁc bamboo region,American bamboo region,African bamboo region and European and North American region (Table 2).The Asia–Paciﬁc bamboo region is the largest bamboo growing area in the world.In Asian countries,bam-boo is known by different names,In China it is known as ‘‘friend of people’’,‘‘wood of the poor’’in India,‘‘the brother’’in Vietnam [33,34].FAO provided the data of bamboo production at global le-vel as shown in Fig.1.In Asia,large area of bamboo is occupied by six countries viz.India,China,Indonesia,Philippines,Myanmar,Vietnam and others.Globally among sympodial and monopodial,sympodial type of bamboo dominates major part [30].The exten-sive awareness of bamboo plantation in China has lead to an in-crease in monopodial bamboo by about 30%.3.2.Extraction of bamboo ﬁbresThe bamboo ﬁbre is obtained from bamboo tree and it is divided into two kinds of ﬁbre according to different process ﬂow and method:Natural original bamboo ﬁbre and bamboo pulp ﬁbre (namely bamboo viscose ﬁbre or regenerated cellulose bamboo ﬁ-bre).Original bamboo ﬁbre is directly picked up from natural bam-boo without any chemical additive,using physical and mechanical method.In order to differentiate from bamboo pulp ﬁbre (bamboo viscose ﬁbre),we call it as original bamboo ﬁbre or pure natural bamboo ﬁbre.But bamboo pulp (viscose)ﬁbre belongs to regener-ated cellulose ﬁbre as chemical ﬁbre.Broadly there are two types of processing to obtain bamboo ﬁbres viz.mechanical processing and chemical processing.Both processes initially include splitting of bamboo strips,which is followed by either mechanical process-ing or chemical processing depending upon the further use of bam-boo ﬁbres.Chemical processing includes initial alkali hydrolysis (NaOH)to yield cellulose ﬁbres.Alkali treated cellulose ﬁbres are then passed through carbon disulphide via multi phase bleaching.Most of the manufactures use this process as it is least time con-suming procedure to yield the bamboo ﬁbres.However,in mechanical process,the initially crushed bamboo is treated by enzymes leading to formation of spongy mass and by the help of mechanical comb ﬁbre technology,individual ﬁbres are obtained.This method is environment friendly as compared to chemical process,although it is less economic process.Research-ers reported detailed method of ﬁbre extraction and it was divided into rough and ﬁne bamboo preparation [35].The rough bamboo ﬁbres were obtained by cutting,separation,boiling and fermenta-tion with enzymes of bamboo.While as to obtain ﬁne bamboo,the steps followed are boiling,fermentation with enzyme,wash and bleach,acid treatment,oil soaking and air-drying.The detailed out-line is given in Fig.2.3.3.Chemical composition and structure of bamboo ﬁbresThe chemical composition of bamboo ﬁbre constitutes mainly cellulose,hemicelluloses and lignin.These components are actu-ally same high-glycans,and make about 90%of total weight ofTable 2Bamboo regions along with countries [30].Bamboo region Countries–PaciﬁcChina,India,Burma,Thailand,Bangladesh,Cambodia,Vietnam,Japan,Indonesia,Malaysia,Philippines,Korea and Sri Lanka2.American bamboo region (Latin America,South America and North America)Mexico,Guatemala,Costa Rica,Nicaragua,Honduras,Columbia,Venezuela and Brazil3.African bamboo region Mozambique,Eastern Sudan4.European countriesEngland,France,Germany,Italy,Belgium,Holland.United States and Canada have introduced a large number of bamboo species from Asian and Latin American bamboo-producing countriespercentage of bamboo from different continents H.P.S.Abdul Khalil et al./Materialsbamboo ﬁbre.The other constituents are protein,fat,pectin,tan-nins,pigments and ash.These constituents play important role in physiological activity of bamboo and they are found in cell cavity or special organelles.The chemical composition of the bamboo ﬁ-bre is given in Fig.3[36].Usually the chemical content of bamboo changes with age of the bamboo,particularly cellulose content keeps on decreasing while age of bamboo is increased so directly it directly affects the chemical composition of bamboo ﬁbre.The lignin is considered to provide stiffness and yellow colour to bam-boo ﬁbres.Different treatments cannot remove all the lignin con-tent of the bamboo ﬁbres,as lignin has been found quite resistant to various alkalis.Non cellulosic components have en-ough contribution to ﬁbre properties such as strength,ﬂexibility,moisture,and even density [37].The unidirectional arrangement of bamboo ﬁbres in tissues and cell wall structure of bamboo is one of unique property of bamboo [38–40].Bamboo ﬁbres possess alternate broad and narrow polylamellate structure with alternat-ing broad and narrow lamella as compared to sandwich like struc-ture of wood ﬁbre [41,42].One the characteristic of ultra structure of bamboo ﬁbre is variation in arrangement of cellulose ﬁbrils along their longitudinal axis.The alternate narrow and broad lay-ers have different arrangement of cellulose microﬁbrils,with largefor covalent bonding in the cell wall structure.This variation of dif-ferent components across the cell wall provides novel design to bamboo ﬁbre wall,enhancing its various mechano-physical prop-erties [38,43,44].Recently,two researchers reported extensive studies on structure of bamboo ﬁbre of different species and inves-tigated the cell wall structure of different bamboo species [45,46].A study on bamboo species Guadua angustifolia revealed the pres-ence of irregular form and more precisely beam shaped pattern of bamboo ﬁbres (Fig.4)[45].Their size was found to depending upon the position across the cell wall.However,irrespective of po-sition of bamboo ﬁbre across the cell wall,a ﬁbre with pentagonal or hexagonal,arranged in a honeycomb pattern was observed.The morphology of bamboo ﬁbres revealed the clean surface of bamboo ﬁbre with no apparent damage,the roughness found at surface will help in ﬁbre matrix bonding,the main utilization of bamboo ﬁbres (Fig.5).They also reported the insight about the ﬁ-bre dimensions of different species of bamboo ﬁbre obtained from different position of respective bamboo culms (Fig.6)[46].The polylamellate structures do not exist in the cell wall of the ﬁbres of the normal wood.Based on its anatomical properties,ultra structure and plant fracture mechanism bamboo establishes itself as a superior natural ﬁbre.4.Eco bamboo ﬁbre compositesScientists have welcomed the move of imposing regulations for better and safer environment and had given a new direction to researchers towards generation of new ideas in eco-composite technology [47–49].Eco-composite can be deﬁned as composites with better environmental and ecological advantages over syn-thetic or conventional composites.Eco-composites can be fabri-cated from natural ﬁbres or variety of natural polymers and polymer matrices.This ﬁeld has gained enough popularity in re-cent years and keeps on increasing day by day,although much has not been achieved yet.4.1.Polyester based bamboo ﬁbre reinforced compositesNatural ﬁbre composites had gained much attention in struc-tural applications in recent years.But this natural material is extre-mely difﬁcult to be produced.Thus,defected material with different degree of cracks may occur during service.Therefore,it is necessary to understand how these difﬁculties may be overcome.It has beenFig.2.Extraction of rough and ﬁne bamboo ﬁbre [35].Fig.3.Chemical constituents of Bamboo ﬁbre [36,37].reported that toughness of a brittle polymer for example,polyester can be improved through naturalﬁbre reinforcement[50].In an interesting study,researchers have selected the bambooﬁbre to study the fracture behaviour of bambooﬁbre reinforced polyester composites[51].These composites were characterized by different approach utilizing a technique known as LEFM approach.In another study,they reported comparison study on bamboo and otherﬁbres used as reinforcement in polyester matrix[52].They developed a composite material of high strength and light weight applications. Effect of different properties viz mechanical and water absorption of bamboo reinforced polyester composites have been reported [53].In order to yield better properties results they have physically modiﬁed the bambooﬁbre by different concentration of NaOH.Tensile andﬂexural strength were extensively studied and the enhanced results were attributed to the less water uptake by the composites by alkali treatments making them more durable.In an-other recently published work,they used different chemicals to modify the bambooﬁbre to estimate various mechanical,physical and morphological properties of bamboo reinforced polyester com-posites[54].They concluded that obtained results from various modiﬁcations of bambooﬁbre show variation in mechanical,phys-ical and morphological properties of bamboo reinforced polyester composites.Maleic anhydride treatment improved the mechanical(Modu-lus of elasticity andﬂexural modulus)as well as water-resistant properties(water uptake)of bamboo–epoxy composites,similarFig.4.Bamboo microstructure[45].images of bamboo(G.angustifolia)ﬁbre bundle after mechanical extraction.Note:Theﬁbre bundle is composed of several elementaryﬁbres, bamboo(G.angustifolia)showing the roughness of theﬁbre bundle after mechanical extraction[45].trend was observed in the properties of other chemically modiﬁed (permanganate and benzoylation treatments)bambooﬁbre poly-ester composites.They supported theirﬁndings of mechanical properties by observing the scanning electron microscope(SEM) images which revealed thatﬁbre-polyester bonding was improved by using modiﬁed bambooﬁbres in composites.Previous research investigated acrylonitrile treated bambooﬁbres reinforced com-posites and observed that acrylonitrile treated bambooﬁbres af-fected the tensile,ﬂexural,and water absorption properties of composites[55].They also studied morphological properties of composites,it exhibited fractured surfaces due to arose tension, enough quantity of residual resin occurred on the surface with gaps between the cells.Further study,they reported water absorb-ing properties of bamboo reinforced polyester composites[56].In this study mercerized bambooﬁbres,modiﬁed by various silanes were carried out to observe the changes in water up taking capac-ity of composites.The main aim of their study was to visualize the hydrophilic character of bamboo based reinforced composites in order to support the current demand of utilization of bamboo in outdoor applications.In another study,researchers reported the use of extracted bambooﬁbres as reinforcement for polymers [12].The overall objective of this work was to investigate theﬁbre extraction from bamboo strips and the use of these bambooﬁbres as reinforcement for polymers,utilizing both chemical and mechanical means to obtain the bambooﬁbres.The developed polyester bamboo reinforced composites were analyzed to yield information about tensile strength and morphological properties.Researchers developed bamboo reinforced polyester compos-ites by hand lay-up technique and bamboo strips used were trea-ted by alkali prior to further studies[57].They also studied effect of bambooﬁbre loading variations on mechanical properties of bamboo reinforced polyester composites and observed best results at60%ﬁbre loading.The interaction between matrix and bamboo ﬁbre was supported by fourier transform infrared spectroscopy (FT–IR),and revealed that hydrogen bonding is main cause of inter-action between theﬁbre and matrix.The fractured surfaces with varied degree of topography were visualized by SEM studies.Bond-ing interaction between the polyester and modiﬁed bamboo was observed with least pull out of celluloseﬁbrils.As it is evident that naturalﬁbres are sensitive to alkali treatment and hence it get dis-solved during treatment which makes fracture in theﬁbre from the lumen,longer celluloseﬁbre pull-out from hemicellulose–lignin matrix was reported in this study.The mechanical,thermal,and morphological properties of polycaprolactone and bambooﬁbre species of bamboo[46].358H.P.S.Abdul Khalil et al./Materials and Design42(2012)353–368composites were evaluated[58].In order to attain the homogene-ity between matrix and the bambooﬁbre,the maleic anhydride grafted polycaprolactone was used for the study.The mechanical (Tensile and elongation at break)properties of bambooﬁbre/ maleic anhydride grafted polycaprolactone composites enhanced as compared to the bambooﬁbre/polycaprolactone composite.4.2.Epoxy based bambooﬁbre reinforced compositesThe adhesive wear and frictional performance of bambooﬁbre reinforced epoxy composites were studied[59].It reported that wear performance of bambooﬁbre reinforced epoxy resin compos-ite had excellent wear resistance,as compared to neat epoxy.The friction performance of bambooﬁbre reinforced epoxy composite was enhanced by almost44%at low sliding velocity for anti parallel orientation as compared to the higher sliding velocity.Morphology of these composites exhibited superior orientation in antiparallel direction as compared to other directions.This observation was attributed to high shear resistance incurred by the bambooﬁbre that inﬂuenced the wear and friction for the different sliding veloc-ities.Another study reported about mercerized the bambooﬁbres to yield the bambooﬁbre-reinforced epoxy composites[60].The re-sulted composites possess of twoﬁbre orientations parallel and perpendicular to the electricﬁeld was achieved.The effects ofﬁbre alignment and alkali treatment on the dielectric properties of bam-booﬁbre epoxy composites and to evaluate the performance of a standard laminating resin was their main concern on the basis of structural concern.The dielectric,electric modulus,AC,and DC con-ductivity studies were carried out to explain the dielectric behav-iour of bamboo epoxy composites.These characteristic properties such as high volume resistivity,good mechanical properties and less cellulose content and small microﬁbrillar angle of bambooﬁbre makes bambooﬁbre reinforced epoxy composites as cost effective biocomposites used for dielectric application.In an interesting study,researchers investigate the effect of silanes on mechanical properties of bambooﬁbre–epoxy composites[56].They prepared two sets of bamboo–epoxy composites,one with silane treatment bamboo mats and the other with silane treatment mercerized bam-boo mats.The mechanical properties such as tensile strength,elas-tic modulus,ﬂexural strength andﬂexural modulus were evaluated and it was observed that silane treatment improved the tensile and ﬂexural strength but addition of silane treated mercerized bamboo leads to the signiﬁcant reduction of the strength.Morphologies, mechanical and thermal properties of bamboo husk reinforced composites were investigated[61].SEM studies revealed that mor-phology ofﬁbres modiﬁed by coupling agents were better in the compatibility with polymer matrices perspective as compared to untreatedﬁbres.It was reported that these composites have high storage modulus and glass transition temperature.Developed a no-vel mechanical extraction process to obtain long bambooﬁbres and were used to fabricate epoxy reinforced structural composites[45]. They mentioned that treatment ofﬁbres by alkali provides a plus point for favouring the bond with the matrix as this treatment re-moves organic and other impurities form theﬁbres hence enhances the interfacial bonding.Theﬂexural and Young’s modulus was also calculated theoretically and good results were obtained forﬁbre/ matrix adhesion andﬁbre alignment.The effect of different deriva-tive of silanes in addition to alkali treatment on water absorption properties of bamboo epoxy composites were extensively carried out[62].Both alkali as well as silane treatment resulted in reduc-tion of water absorption.The results obtained by them were attrib-uted to improvedﬁbre–matrix adhesion,resulting from the alkali and silane treatment.The main cause of less water absorption is greater hydrophobicity developed by treatment of bambooﬁbres. Among the different silanes used in this study amino functional si-lanes provided best results with epoxy resins.Triethoxy derivative gave better results than trimethoxy amino silacanes,however,the best water absorption results were achieved by alkali and amino-propyltriethoxysilane treated bamboo–epoxy composite.In their study,a similar type of study was carried out with no alkali treat-ment was given to bambooﬁbres[63].The amino silanes have reduced the water absorption capacity of bamboo reinforced epoxy composites to greater extent as compared to untreatedﬁbre composites.It was observed that aminopropyltriethoxy silane exhibited good results for bamboo–epoxy composites than the aminopropyltrimthoxy silane.Similar explanation stated as above was justiﬁed for the results obtained in this study,which indicates the better adhesion ensured better adhesion between epoxy matrix and bamboo hence leading to reduced water absorption in compos-ites.Aminopropyltriethoxy silane treated bambooﬁbre composite yielded good results against water absorption,and was supported by their lowest diffusion coefﬁcient values.The overall perfor-mance of fabricated composite depends on various physico-mechanical properties particularly void content.It reported a short bambooﬁbre reinforced epoxy composites and their density,void content,and percent weight reduction from the matrices[64]. The void content directly depends on theﬁbre content used,and it was observed that void content of these composites keep on decreasing with increasingﬁbre content.Similar trend was observed with density of these composites.A linear relationship was observed for weight reduction for these composites as function of matrix with linear increase,hence generating light weight composites.4.3.Phenolic resin based bambooﬁbre reinforced compositesResearchers investigated the effect of mercerization of bamboo ﬁbre on physical,mechanical and thermal behaviour(weathering behaviour,%water uptake,%thickness swelling,and thermal sta-bility)of bambooﬁbres reinforced novolac resin composites (Fig.7)[65].The effect of mercerization of both treated and un-treated on properties of composites were evaluated.Earlier reports clariﬁed that these modiﬁcation improve various properties such as wetting ability,interfacial strength,mechanical properties, weathering and thermal properties of the composites[19].The weathering behaviour,water absorption,humidity and UV expo-sure along with dimensional changes of fabricated composites were carried out for different duration and atmospheric conditions. They reported that better thermal properties were observed after alkali treatment due to better interfacial interaction between alkali treated bambooﬁbres and novalic resin.As per their evaluation, they hypothesized that alkali treatment makes fabricated compos-ites more thermally stable up to certain range of temperature and at particular concentration of alkali.In addition,moisture absorp-tion at100%humidity was considered to be depending on interfa-cial bonding.The Dynamic mechanical analysis(DMA)of a composite material directly depends on various factors e.g.ﬁbre content,compatibilizer,additive,orientation of theﬁbre and the mode of testing plays important role.There are various studies re-ported earlier in which these study has been utililized[66–68]. Similar studies on dynamic mechanical and thermal properties of novolac–bambooﬁbre composites were reported[69].Prior to composite fabrication the bambooﬁbres were treated with alkali and it shows that obtained properties were affected by the concen-tration of alkali used.Thermal degradation studies revealed that al-kali treatment of theﬁbre imparts better thermal stability to the composites as compared to untreated one.FT–IR and DMA obser-vations suggested that best results were obtained for20%alkali-treatedﬁbre composites.The fabricated bambooﬁbre reinforced novolac composites were characterized for their visco-elastic prop-erties and it was best technique which provides the most appropri-ate information about the glass transition temperature asH.P.S.Abdul Khalil et al./Materials and Design42(2012)353–368359。

土木工程外文翻译(中英互译版)

使用加固纤维聚合物增强混凝土梁的延性Nabil F. Grace, George Abel-Sayed, Wael F. Ragheb摘要：一种为加强结构延性的新型单轴柔软加强质地的聚合物(FRP)已在被研究，开发和生产(在结构测试的中心在劳伦斯技术大学)。

这种织物是两种碳纤维和一种玻璃纤维的混合物，而且经过设计它们在受拉屈服时应变值较低，从而表达出伪延性的性能。

通过对八根混凝土梁在弯曲荷载作用下的加固和检测对研制中的织物的效果和延性进行了研究。

用现在常用的单向碳纤维薄片、织物和板进行加固的相似梁也进行了检测，以便同用研制中的织物加固梁进行性能上的比拟。

这种织物经过设计具有和加固梁中的钢筋同时屈服的潜力，从而和未加固梁一样，它也能得到屈服台阶。

相对于那些用现在常用的碳纤维加固体系进行加固的梁，这种研制中的织物加固的梁承受更高的屈服荷载，并且有更高的延性指标。

这种研制中的织物对加固机制表达出更大的奉献。

关键词：混凝土，延性，纤维加固，变形介绍外贴粘合纤维增强聚合物〔FRP〕片和条带近来已经被确定是一种对钢筋混凝土结构进行修复和加固的有效手段。

关于应用外贴粘合FRP板、薄片和织物对混凝土梁进行变形加固的钢筋混凝土梁的性能，一些试验研究调查已经进行过报告。

Saadatmanesh和Ehsani〔1991〕检测了应用玻璃纤维增强聚合物(GFRP)板进行变形加固的钢筋混凝土梁的性能。

Ritchie等人〔1991〕检测了应用GFRP，碳纤维增强聚合物〔CFRP〕和G/CFRP板进行变形加固的钢筋混凝土梁的性能。

Grace等人〔1999〕和Triantafillou〔1992〕研究了应用CFRP薄片进行变形加固的钢筋混凝土梁的性能。

Norris，Saadatmanesh和Ehsani〔1997〕研究了应用单向CFRP薄片和CFRP织物进行加固的混凝土梁的性能。

在所有的这些研究中，加固的梁比未加固的梁承受更高的极限荷载。

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Effect of Bagasse Fiber on the Flexural Properties of Biodegradable CompositesShinichi Shibata,Yong Cao,Isao FukumotoDepartment of Mechanical Systems Engineering,University of the Ryukyus,Nishihara Okinawa903-0213, JapanFlexural modulus of the press-molding composites made from bagasseﬁber and biodegradable resin was investigated by experiment and numerical prediction with Cox’s model that incorporates the compression ratio of the bagasseﬁber in the cross section.The effect of the volume fraction of bagasseﬁber and its length on theﬂexural modulus was examined.Up to65%volume fraction in the experiment,theﬂexural modulus in-creased with increase of the volume fraction of the bag-asseﬁber.The numerical prediction was in good agree-ment with the experimental result.Above65%volume fraction,however,theﬂexural modulus decreased in the experiment,while the prediction increased.It seemed that the biodegradable resin was insufﬁcient to cover all the surface of bagasseﬁber in the composite.Moreover, the decrease of theﬂexural modulus was found below3 mm at theﬁber length in the experimental and the same trend was shown in the numerical prediction.POLYM. COMPOS.,26:689–694,2005.©2005Society of Plastics Engi-neersINTRODUCTIONComposites reinforced with naturalﬁbers such as kenaf [1],jute[2–4],ramie,oil palm[5],hemp[6],and bagasse [7]have been the subject of intense study for cost,speciﬁc gravity,and ecological reasons.Especially,many studies [8–11]on the composites combined with biodegradable resins have been performed to improve the mechanical properties,which are inferior to conventional composites such as polypropylene and glassﬁber.Among them,bag-asseﬁber is of interest from the point of view that bagasse ﬁbers are the remains of squeezed sugar cane.Moreover,the worldwide production of bagasseﬁber isϳ7times larger than that of jute,kenaf,and hemp combined[12].Thus,the bagasseﬁber composites have considerable potential to become a substitute material for conventional composites.On the other hand,as far as we know,there are few studies that predict theﬂexural modulus of those natural ﬁber composites.Above all,bagasseﬁber is expected to be compressed in a press-molding because bagasseﬁber has a honeycomb structure due to the liquor extraction in a sugar mill.This compression should be incorporated in the pre-diction model.The objective of the present study is to predict the ﬂexural modulus of the composites made from bagasseﬁber and biodegradable resin.In order to achieve this purpose, the composites were fabricated by a press-molding and the ﬂexural modulus was examined in view of the volume fraction of the bagasseﬁber and itsﬁber pared to these experimental results,the numerical prediction of the ﬂexural modulus was performed with Cox’s model[13], which incorporates the compression ratio of bagasseﬁber.MATERIALS AND METHODSFiber and PolymerBagasseﬁber,obtained as the leftover after liquor ex-traction in a sugar mill,was dried for72h at80°C.Then the bagasseﬁber was chopped and sieved by four sizes.These ﬁber lengths(diameters)averaged1.6mm(0.22mm),3.2 mm(0.37mm),9.1mm(0.37mm),and16.1mm(0.41 mm).The biodegradable resin,CP-300,was a cornstarch base supplied from Miyoshi Oil Fat(Japan).The resin was originally an emulsion type,then it was dried and chopped into pellets1–2mm in diameter.The mechanical properties of the resin at26°C are shown in Table1with subscripts “m.”The bagasse-biodegradable resin composites were fab-ricated in the form of a cylindrical steel mold(30mm in diameter).The mold was heated to160°C for15min.After the temperature reached158–162°C,the materials were pressed in the cylinder and held at10MPa for10min.The fabricated composites were30mm in diameter and1.8–1.9 mm in thickness and disc-shaped.MeasurementTo determine Young’s modulus of the bagasseﬁber,72ﬁbers were tested.Span length and a crosshead speed wereCorrespondence to:Shinichi Shibata;e-mail:shibata@tec.u-ryukyu.ac.jp DOI10.1002/pc.20140Published online in Wiley InterScience().©2005Society of Plastics EngineersPOLYMER COMPOSITES—200515mm and 1mm/min with a testing machine (Shimazu,type DCS-R-100,Japan).Randomly chosen bagasse ﬁbers were mounted on a paper tab with both ends of the bagasse ﬁber glued.The diameters were measured at three different points with an optical projector (Nikon,type V16-D,Japan),assuming that the bagasse ﬁber was cylindrical.Figure 1shows the result.The tensile strength and Young’s modulus were 89.9MPa and 4,526MPa.This value was used for the prediction of the ﬂexural modulus.The ﬂexural tests were carried out according to ISO 178using a three-point bending method on ﬁve specimens in each composite.The dimension of the specimen was 30ϫ15ϫ1.8–1.9mm.The tests were performed at room temperature (26°C)in order to avoid the inﬂuence of tem-perature on the ﬂexural properties [14].Span length and a crosshead speed were 18mm and 1mm/min.Flexural modulus and strength were determined by the inclination of the initial line and the maximum load on the load-displace-ment curve.Prediction of Flexural ModulusIt is well known [14]that Young’s modulus of short ﬁber reinforced composites is determined by:E comp ϭ␩␽␩f V f E f ϩ͑1ϪV f ͒E m ,(1)where E f ,E m ,V f ,and V m denote the Young’s modulus of the ﬁber,the matrix,the volume fraction of the ﬁber and the matrix,respectively.␩f ,␩␪denote efﬁcient factors of ﬁber length and orientation.␩f is given [15,16]by:␩f ϭ1Ϫ͑tanh 12␤L ͒/12␤L ,(2)␤ϭͩ2G m E f r f 2ln ͑R /r f ͒ͪ1/2.(3)Equation 2shows that the Young’s modulus of the com-posite decreases with decreasing ﬁber length L ,where r f andR denote the radius of the ﬁber and the interval between ﬁbers.If the distribution of the ﬁbers is homogeneous in an ideal packing square composite,R is given by:R ϭr f 2ͱ␲V f.(4)Shear modulus G m assuming that the composite is an isot-ropy given by:G m ϭE m2͑1ϩ␯m ͒,(5)where r f and ␯m denote the radius of the ﬁber and Poisson’s ratio of the matrix that assumed ␯m is 0.3.On the other hand,␩␪has been analyzed in detail by Fukuda and Chou [17].According to their analysis,␩␪is 0.27when the orientation of the ﬁber in the composites is 2D and random.Figure 2shows the ﬁber orientation distri-bution on the surface region of the composite.The orienta-tion angles of 200randomly chosen ﬁbers weremeasured.FIG.1.Young’s modulus of bagasse ﬁbers as a function of ﬁber diam-eter.FIG.2.Distribution of the orientation angle of the composites.TABLE 1.Mechanical properties of bagasse ﬁber and biodegradableresin.Parameter Value ␴f 89.9MPa ␴m 24.0MPa E f 4,526MPa E m 520MPa ␳f 0.341kg/cm 3␳m 1.160kg/cm 3R f 0.40mm V bf 1.14mm 3f n4,654g Ϫ1690POLYMER COMPOSITES—2005The orientation angle was deﬁned as the angle between the ﬁber direction and the longitudinal direction of the ﬂexural specimen.The ﬁber orientations were so randomly dis-persed that ␩␪is assumed to be 0.27.Finally,we bring the compression ratio of the bagasse ﬁber,K ,into Eq.1.The compression ratio is deﬁned as the inverse number of the ﬁber volume in the specimen corre-sponding to the original ﬁber volume.Hence,the compres-sion ratio,K ,is calculated by:K ϭ͑f m V bf ͒/ͫV ϪͩW ϪW f␳mͪͬ,(6)where f n ,V bf ,V ,W ,W f ,and ␳m denote the number of ﬁbers,volume of a ﬁber,volume of the composite,weight of the composite,weight of the ﬁbers,and density of the matrix,respectively.This compression ratio reﬂects the effect of the ﬁber compression on the reinforcement of the composites.Therefore,the ﬁnal equation that predicts ﬂexural modulus of the composites is:E comp ϭK ␩␽␩f V f E f ϩ͑1ϪV f ͒E m .(7)RESULTS AND DISCUSSIONEffect of Volume Fraction of Bagasse Fiber on the Flexural ModulusFigure 3shows the variation of the compression ratio calculated by Eq.6with varying the volume fraction of the bagasse ﬁber.The transformation of the weight fraction into the volume fraction of the ﬁber is calculated by:V f ϭͫV ϪͩW ϪW f␳mͪͬ/V ,(8)where W f ,␳m ,V ,and V f denote the ﬁber weight,the density of the matrix,the volume of the specimen,and the volume fraction of the ﬁber,respectively.The compression ratio was ϳ3.4above the volume frac-tion 30%.The compression ratio,however,was 4.2at 19%volume fraction.The reason why the compression ratio at 19%was higher than any other volume fractions is not obvious.However,this higher compression may be attrib-uted to the high resin volume fraction caused by optimized movement of the bagasse ﬁbers in the press-molding,re-sulting in the high compression ratio.Next,the cross section of the composites was polished and observed with an optical microscope.As shown in Fig.4a,it was observed that the bagasse ﬁber and the biodegradable resin were clearly sep-arated.However,in very few cases the bagasse ﬁber,which had permeated the biodegradable resin,was found as shown in Fig.4b.A similar microstructure was reported intheFIG.3.Effect of the volume fraction of bagasse ﬁbers on the compres-sionratio.FIG.4.Optical microphotographs of the bagasse ﬁber.a:The bagasse and the biodegradable resin.b:The bagasse ﬁber has permeated the biodegradable resin.POLYMER COMPOSITES—2005691study by Cichocki and Thomason [18].Furthermore,Fig.5a,b shows SEM micrographs of the raw bagasse ﬁber and the compressed bagasse ﬁber on the fracture surface.It was found that the bagasse ﬁber that has originally a honeycomb structure was compressed.Also,the resin was not perme-ated in the honeycomb structure.The percentage of the area of cells on the honeycomb structure including cavities was ϳ25%.Hence,it is considered that the obtained compres-sion ratio,3.4,is equal to the actual compression ratio of the bagasse ﬁber.Figure 6a shows the side view of a raw bagasse ﬁber in which the surface was a rough structure.On the other hand,a bagasse ﬁber wetted by resin on the fracture surface is shown in Fig.6b.This photograph shows that the ﬁber was completely wetted by resin and resulted in better interfacial adhesion.Similar observations were reported by Karnani et al.[10]and Hoecker et al.[20].Thus,the ﬂexural modulus can be predicted by Eq.7,which assumes that the ﬁber and matrix is well bonded enough to transfer stress among ﬁbers in the composite.Figures 7and 8show the variation of the ﬂexural mod-ulus and ﬂexural strength with varying the volumefractionFIG.5.SEM microphotographs of (a)a cross section of a raw bagasse,and (b)a compressed bagasse ﬁber on the fracturesurface.FIG.6.SEM microphotographs of (a)side view of a raw bagasse,(b)a bagasse ﬁber wetted by resin on the fracturesurface.FIG.7.Variation of the ﬂexural modulus with varying volume fraction of bagasse ﬁbers.692POLYMER COMPOSITES—2005of the bagasse ﬁber.The lines were predicted applying Eq.7with the parameters shown in Table 1.The ﬂexural modulus increased gradually with increas-ing the volume fraction of the bagasse ﬁber up to 65%(2,525MPa)as well as the ﬂexural strength.In this region,the rule of mixtures was afﬁrmed.However,the ﬂexural modulus decreased at 74%.In this case,by visual observa-tion of the surface of the specimen,it was observed that there were bagasse ﬁbers that had not wetted with the biodegradable resin.This is the reason why the volume fraction of 65%was seen in the maximum ﬂexural modulus.The prediction at K ϭ 5.0and 2.0is far from the experimental results while the line,K ϭ3.4,is close to that.Hence,it is considered that the estimation of the compres-sion ratio,K ϭ3.4,was correct in predicting the ﬂexural modulus.Effect of Fiber Length on the Flexural ModulusIn the previous section the ﬂexural modulus showed its maximum 2,525MPa at 65%volume fraction.Then,at the volume fraction the effect of the ﬁber length on the ﬂexural modulus was examined.Figures 9and 10show the variation of the ﬂexural modulus and strength with varying the bag-asse ﬁber length.The ﬂexural modulus rapidly decreased at 1.6mm ﬁber length.The lines on the ﬁgure are predicted applying Eq.7as well as the previous section.The estima-tion at K ϭ3.4shows good agreement with the experimen-tal results,while K ϭ5.0and 2.0is far from the result.In addition,below the bagasse ﬁber length of 3mm a decrease of the ﬂexural modulus was seen.The compression ratio below 3mm in ﬁber length was rather higher than that above ﬁber length;this decrease is due to the shortening in the ﬁber length as described in Eq.2.In other words,the efﬁciency of stress transfer between ﬁbers decreased with a decrease of ﬁber length,and the lower efﬁciency resulted inlower ﬂexural modulus.The aspect ratios of ﬁber lengths 3and 1.6mm were ϳ12and 8.The relationship between ﬂexural modulus and ﬁber length in a short ﬁber-reinforced plastic was investigated by Hsueh [19].According to those results,the ﬂexural modulus sharply decreases below aspect ratio 10.In this study,the aspect ratio was 22in ﬁber length 9.1mm and the decrease of ﬂexural modulus was not conﬁrmed,while the decrease was clearly found in an aspect ratio of 8in ﬁber length 1.6mm.Thus,that analysis is in good accordance with the obtained results.Figure 11shows the variation of the compression ratios with varying ﬁber length.The compression ratio decreases with an increase of ﬁber length.The reason for this is not obvious;however,the decrease of the ﬁber length may enable the bagasse ﬁber to move into an optimizedpositionFIG.8.Variation of the ﬂexural strength with varying volume fraction of bagasseﬁbers.FIG.9.Variation of the ﬂexural modulus with varying the bagasse ﬁberlength.FIG.10.Variation of the ﬂexural strength with varying the bagasse ﬁberlength.POLYMER COMPOSITES—2005693during press-molding and this may contribute to the shorter ﬁber length and the higher compression ratio. CONCLUSIONTheﬂexural modulus of the composites made from bag-asseﬁber and the biodegradable resin increased with in-creasing the volume fraction of the bagasseﬁber up to65%. However,at75vol%theﬂexural modulus decreased be-cause the biodegradable resin was insufﬁcient to cover all the surface of the bagasseﬁber.Hence,the predictedﬂex-ural modulus by Cox’s model is in good agreement with the experimental result up to65volume fraction.The compres-sion ratio incorporated into Cox’s model wasϳ3.4.Accord-ing to the optical microstructure observation,there were few bagasseﬁbers that permeated the resin and theﬁber was actually compressed to30%of the original volume.In65%volume fraction,the decrease of theﬂexural modulus was seen belowﬁber length3mm(aspect ratio 12).This result was in good agreement with the numerical calculation based on Cox’s model.Moreover,the compres-sion ratio decreased with an increase of the bagasseﬁber length.This result may reﬂect that the shorterﬁber length enabled theﬁbers to move into an optimized position during press-molding.REFERENCES1.T.Nishino,K.Hirao,M.Kotera,K.Nakamae,and H.Inagaki,Compos.Sci.Technol.,63,1281(2003).2.T.M.Gowda,A.C.B.Naibu,and R.Chhaya,Compos.PartA–Appl.S.,30,227(1999).3.D.Ray,B.K.Sarkar,A.K.Rana,and N.R.Bose,Compos.PartA–Appl.S.,32,119(2001).4.J.Gassan,Compos.Part A–Appl.S.,33,369(2002).5.M.Wollerdorfer and H.Bader,Ind.Crop.Prod.,8,105(1998).6.A.Keller,Compos.Sci.Technol.,63,1307(2003).7.M.V.de Sousa,S.N.Monteiro,and J.R.M.d’Almeida,Polym.Test.,23,253(2004).8.S.H.Aziz and M.P.Ansell,Compos.Sci.Technol.,64,1219(2004).9.A.K.Rana,A.Mandal,and S.Bandyopadhyay,Compos.Sci.Technol.,63,801(2003).10.R.Karnani,M.Krishnan,and R.Narayan,Polym.Eng.Sci.,37-2,476(1997).11.A.Keller,Compos.Sci.Technol.,63,1307(2003).12.J.E.Atchison,Pulp Paper,69,7,125(1995).13.H.L.Cox,Br.J.Appl.Phys.,55,72(1952).14.B.Wielage,mpke,H.Utschick,and F.Soergel,J.Mater.Process.Tech.,139,140(2003).15.D.Hull,An Introduction to Composite Materials,CambridgeUniversity Press,Cambridge,UK(1982).16.Y.Sanomura and M.Kawamura,pos.,24,5,587(2003).17.H.Fukuda and T.W.Chou,J.Mater.Sci.,17,1003(1982).18.F.R.Cichocki Jr.and J.L.Thomason,Compos.Sci.Technol.,62,669(2002).19.C.H.Hsueh,Compos.Sci.Technol.,60,2671(2000).20.F.Hoecker,K.Friedrich,H.Blumberg,and J.Karger-Kocsis,Compos.Sci.Technol.,54,317(1995). FIG.11.The effect of the bagasseﬁber length on the compression ratio.694POLYMER COMPOSITES—2005。

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