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1、Statistical Tensile Strength for High Strain Rate of Aramid and UHMWPE Fibers46材料工程/2006年5期StatisticalTensileStrengthforHighStrainRateofAramidandUHMWPEFibersYANGBin.XIoNGTao,XIONGJie(KeyLaboratoryofAdvancedTextileMaterialsandManufacturingTechnology,MinistryofEducation,ZhejiangSciTechUniversity,Hangz
2、hou310018,China)Abstract:Dynamictensileimpactpropertiesofaramid(Technora)andUHMWPE(DC851)fiberbundleswerestudiedattwohighstrainratesbymeansofreflectingtypeSplitHopkinsonBar,andstressstraincurvesoffiberyarnsatdifferentstrainrateswereobtained.Experimentalresultsshowthattheinitialelasticmodulus,failure
3、strengthandunstablestrainofaramidfiberyarnsarestrainrateinsensitive,whereastheinitialelasticmodulusandunstablestrainofUHMWPEfibervamsarestrainratesensitive.Afiber-bundlestatisticalconstitutiveequationwasusedtodescribethetensilebehaviorofaramidandUHMWPEfiberbundlesathighstrainrates.Thegoodconsistency
4、betweenthesimulatedresultsandexDerimenta1dataindicatesthatthemodifieddoubleWeibullfunctioncanrepresentthetensilestrengthdistributionofaramidandUHMWPEfibersandthemethodofextractingWeibullparametersfromfiberbundlesstressstraindataisvalid.KeywOrds:aramidfiber;UHMWPEfiber;impactbehaviour;statisticalprop
5、erties;statisticalconstitutiVeequationCLCnumber:TB33Documentcode:AArticleID:1001-4381(2006)05004605Technora,madefromaramidfibersandsomewhatsim订artothecommonlyknowKevlar,andUltrahighlyorientedhighmolecularweightpolyethvlene_UHMWPEfibersarealloftenusedinflexiblearmourapplicationsandhencesubjectedtohig
6、hratesofloading.Theutilizationoftheirreinforcedcompositesarmourincertainballisticapplicationsisincreasinglypreferredoverconventionalrigidmetalarmoursystemsbecauseofitssuperiorstrength.toweightratioandflexibility.Todate,thedesignanddevelopmentofsuchfabricarmoursystemshavelargelybeenapproachedempirica
7、lly卜.Theballisticresistanceoffiberreinforcedcompositeisessentiallydependentonthemechanicalbehaviorofthereinforcingcomponentandthematrix.Fibersandfiberbundlescarrythebulkoftheappliedloadinafiber-reinforcedcomposite.Thustheunderstandingofthestrainratesensitivityofthefibersisveryimportantfortheuseandde
8、signofthefiberreinforcedcomposites.Nevertheless,forTechnoraandUHMWPEfibersandfiberbundles,fewexperimentalresultsonthehighstrainratehavebeenreported.ItiswellknownthatengineeringfibersoftenexhibitabrittlefracturebehaviorandtheirtensilestrengthobeyWeibullstatisticaldistribution.Twoexperimentalmethodsca
9、nbeusedtodeterminethestrengthstatisticaldistributionparametersoffibersunderquasistaticloading.Oneisthesinglefibertestandtheotheristhefiberbundletest一.Thefiberbundletestingmethodisincreasinglyusedtoday.Ontheotherhand,duetothetechniquedifficulty,nosuitableexperimentaltechniqueisavailabletoperformthedy
10、namicsinglefibertensiontests.Therefore,thefiberbundletestingmethodistheonlychoicefordeterminingthedynamictensilestrengthdistributionoffibersunderimpactloadingconditions.一.Inthispaper.tensileimpacttestsofaramid(Technora)andUHMWPE(DC851)fiberbundlesarecarriedoutundertwohighstrainratesbyusingaSplitHopk
11、insonTensileBar(SHTB),andtheexperimentaldataareusedtoderivestatisticalconstitutiveequationofaramidandIIHMPEfiberbundles.Foundationitems:supportedbytheNationalNaturalScienceFoundationofChina(10372092).E-mail:StatisticalTensileStrengthforHighStrainRateofAramidandUHMWPEFibers471ExperimentalApparatusand
12、TensileImpactTestTensileimpacttestswereconductedonthereflectedindirecttensileimpactapparatusfrommodifiedSHPB(SplitHopkinsonPressureBar).Aschematicofthesetupandstresswavepropagation.z-tschemearepresentedinFig.1.Throughtheimpactofthestrikerbarontheoutputbar,producingastresswavevialiningblocktransmitst
13、hroughtheinputbar.Suchstressimpulsetravelsdowntheinputbarandispartiallyreflectedattheinputbar/specimeninterfaceandpartiallytransmittedtothespecimenandtheoutputbar.Measurementsofthereflectedandtransmittedwavesweremadeusingstraingagesarrangedontherespectivebarsofthesystem.Theincidentstraini(t),reflect
14、edstrain(t)andtransmittedstraint(t)arerecordedatstraingagesmountedontheinputbarandoutputbars,respectively.Accordingtotheone-dimensionalsimple-wavetheory,thedynamictensilestress口.(t),dynamictensilestrain.()andstrainrate()inthespecimencanbeobtainedfromthefollowing:伪,l</L2l,:.,一一一一一!A.A1-strikerbar;
15、2-outputbar;3一inputbar;4一absorbingbar;5-superdynamicamplifier;6-transientconverter;7-computer;8-speedometer;9-liningblock;10一specimenFig.1Tensileapparatussketchandstresswavepropagationx-tscheme)(1)(r)(r)dr)一2LC.oi()一()(2)(3)whereEandA0aretheYoungsmodulusandthecrosssectionalareaoftheinput/outputbar,Coisthelongitudinalwavevelocityofthebar,A.andL0arethecrosssectionalareaandgagelengthofthespeci-men,respectively.Thematerialinvestigatedinthispaper
