纺织材料的英文版系列文00004).ppt

《纺织材料的英文版系列文00004).ppt》由会员上传分享，免费在线阅读，更多相关内容在PPT专区-天天文库。

1、Chapter8FiberPropertiesandIdentificationYipingQiuDonghuaUniversityFiberPropertiesandIdentificationMechanicalpropertiesTensilepropertiesTensiledeformationFiberPropertiesandIdentificationTensiledeformation:someconceptsElongationStrainFiberPropertiesandIdentificationTensile

2、deformationLoad:ForceappliedtoextendthefiberUnfairtocompareforceappliedtofiberswithdifferentsizes.StressEngineeringstressUnit:Pa=N/m2ordyne/cm2psi=pound/in2FiberPropertiesandIdentificationTensiledeformationFortextileyarnsandfibers,hardtodeterminecross-sectionareauselinea

3、rdensity:gf/denierorN/texFiberPropertiesandIdentificationTensiletestingoffibersTestingconditions:ASTMstandardfortextiletesting:70°F(21°C)and65%relativehumidity(RH)Stress-straincurvesFiberPropertiesandIdentificationStress-straincurvesInitialmodulusTheslopeofthefirstsectio

4、nofthestress-straincurve(ratioofthestresstostrain)alsocalledYoung’smoduluscloselyfollowsHook’sLawsmallermodulus,easiertoelongateundersmallstresses.Fordifferentapplications,differentrequirements:ordinaryapparels:highinitialmoduluswomen’ssheerhosiery:lowinitialmoduluscompo

5、sites:extremelyhighinitialmodulusFiberPropertiesandIdentificationStress-straincurvesInitialmodulusFiberPropertiesandIdentificationStress-straincurvesYieldpointThepointatwhichthestress-straincurveflattensorchangesitsslopesignificantlyFiberPropertiesandIdentificationStress

6、-straincurvesYieldpointThepolymers“yield”ormolecularchainsstarttomoveandpassoneanother.Thedeformationispermanent.Theslopeofthestress-straincurveafteryieldpointreliesonthestrengthofintermolecularforces.Mostfibershaveyieldpointbutnotcottonandflaxduetostrongintermolecularfo

7、rces.FiberPropertiesandIdentificationStress-straincurvesHardeningpointThepolymermoleculesbecomemoreorientedasstrainincreasesandthefiberreachesadeformationlimit,wherethemoleculeshavethehighestorientationand(stress)hardeningoccurs.FiberPropertiesandIdentificationStress-str

8、aincurvesFailurepointWherethefiberfails.Sometimesnotnecessarythemaximumstresspoint.Dependsondefinition.