简介:Manybiologicalmaterials,suchaswoodandbone,possesshelicoidmicrostructuresatmicroscale,whichcanserveasreinforcingelementstotransferstressbetweencracksurfacesandimprovethefracturetoughnessoftheircomposites.Failureprocesses,suchasfiber/matrixinterfacedebondingandslidingassociatedwithpull-outofhelicalfibers,areresponsiblemainlyforthehighenergydissipationneededforthefracturetoughnessenhancement.Herewepresentsystemicanalysesofthepull-outbehaviorofahelicalfiberfromanelasticmatrixviathefiniteelementmethod(FEM)simulation,withimplicationsregardingtheunderlyingtougheningmechanismofhelicoidmicrostructures.Wefindthat,throughtheiruniformcurvatureandtorsion,helicalfiberscanprovidehighpull-outforceandlargeinterfaceareas,resultinginhighenergydissipationthataccounts,toalargeextent,forthehightoughnessofbiologicalmaterials.Thehelicityoffibershapeintermsofthehelicalanglehassignificanteffectsontheforce-displacementrelationshipsaswellasthecorrespondingenergydissipationduringfiberpull-out.
简介:Out-of-planebucklingofanisotropicelasticplatesubjectedtoasimpleshearisinvestigated.Fromexact3-Dequilibriumconditionsofanisotropicelasticbodywithaplaneofelasticsymmetryatcriticalconfiguration,theequtionforbucklingdirection(bucklingwavedirection)parameterisderivedandtheshapefunctionsofpossiblebucklingmodesareobtained.Thetractionfreeboundaryconditionswhichmustholdontheupperandlowersurfacesofplateleadtoalineareigenvalueproblemwhosenontrivialsolutionsarejustthepossiblebucklingmodesfortheplate.Thebucklingconditionsforbothflexuralandbarrelingmodesarepresented.Asaparticularexampleofbucklingofanisotropicelasticplate,thebucklingofanorthotropicelasticplate,whichissubjectedtosimpleshearalongadirectionmakinganarbitraryangleofθwithrespecttoanelasticprincipalaxisofmaterials,isanalyzed.Thebucklingdirectionvarieswithθandthecriticalamountofshear.Thenumericalresultsshowthatonlytheflexuralmodecanindeedexist.