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1、SurfaceandInterfaceofFibersandCompositesDonghuaUniversityYipingQiuSurfaceandinterfaceSurface=interfacebetweenasolidorliquidandairInterface=betweentwosolidsorliquidsorsolidandliquidSometimes,alsocalledinterphase,athinlayerofmaterialbetweenthetwobulkmaterials.IntroductionThreemajorcomponentsincom
2、positesFibersMatrixInterfaceorinterphaseDefinitionInterface:meansnothicknessmathematicallyInterphase:inreality,thereisatransitionlayerfromthefibertothebulkofmatrixThedifferencebetweenamoleculeonsurfaceandinbulkUnbalancedforcesSurfacetensionOxidizedsurfacelayerSurfacephenomenonSurfaceroughnessSu
3、rfacechemicalcompositionWeakboundarylayerSurfacephenomenonDerivationofYoung’sEquation?LV?SV?SLqSolidLiquidSurfacephenomenonYoungequation:contactangleDupreequation：workofadhesionBondingmechanismsMolecularentanglementfollowinginter-diffusionElectrostaticattractionCationicgroupsattheendofmolecules
4、attractedtoananionicsurfaceChemicalreactionMechanicalkeyingEffectofinterfaceoncompositestrengthThestrongerthebetter?Depends!ThefunctionofinterfaceLoadtransferEnergyabsorptionOthereffects:electric,thermaletc.StressesandStrainsinShortFiberCompositeTheShearLagModelDescribesstressandstraindistribut
5、ionclosetotheendofafiberimbeddedinmatrixAsimplenotveryaccuratebutusefulmodelcomparedwithsomeothermodelsProposedfirstbyCoxanddevelopedbyothersTheShearLagModelShearlagmodelStressandstraindistributionRadialdistributionofshearstressinmatrixnearaloadedfiber:Assumption:theshearforcesontheneighboringa
6、nnuliarethesame:ShearlagmodelShearLagModelTheshearstress?inthematrixatanyradius?isrelatedtotheinterfacialshearstress,?i,ofthefiberandfiberdiameter,?:Theshearstrainofthematrixnearthefiberisafunctionofthedisplacementofthematrix:Whereu-displacement,?-shearstrain,Gm-shearmodulusShearLagModelForanyx
7、,thedifferenceindisplacementatRandthatatrorfibersurfaceShearLagModelIfRislargeenough,thestressisuniformlydistributed.R/rdependsonfibervolumefraction.RecallpreviousdiscussiononpackingoffibersShearLagModelFiberpackingarrangementsFib
