lecture notes 2 interface

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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