材料专业英语复合材料--Composites

MetalsPoorcorrosionResistanceCeramicsBrittleGlassesBrittleElastomersCreepatlowtempPolymersCreepatlowtempCompositesCorrosionresistantLowmodulusHighstrengthHighstrength,Moderatemodulus,HighductilityCompositesReinforcementAMatrixBadvantages*disadvantagesadvantages*disadvantages**C1C3C2Whatarecomposites?Acompositematerialorcompositeisacomplexsolidmaterialcomposedoftwoormorematerialsthat,onamacroscopicscale,formausefulmaterial.Or:Acompositematerial:Consistsoftwoormorephysicallyand/orchemicallydistinct,suitablyarrangedordistributedphases,withaninterfaceseparatingthem.Reinforcementphase:dispersed,non-continuousphase→harderandstronger→Glass,Carbon,Organic,Boron,Ceramic,Metallicmatrix:bulk,continuousphase→Polymers,Metals,CeramicsInterfaceTheessenceoftheconceptofcompositesisthis:thebulkphaseacceptstheloadoveralargesurfacearea,andtransfersittothereinforcement,whichbeingstiffer,increasesthestrengthofthecomposite.AdvantagesHighstrengthandstiffnessLowweightratio——Idealforstructuralapplicationswherehighstrengthto-weightandstiffness-to-weightratiosarerequiredMaterialcanbedesignedinadditiontothestructureCanmanufacturestructuresandeliminatejointsStrength/densitySpecificStrength&SpecificModulusTypesofCompositesMatrixphase/ReinforcementPhaseMetalCeramicPolymerMetalPowdermetallurgyparts–combiningimmisciblemetalsCermets(ceramic-metalcomposite)BrakepadsCeramicCermets,TiC,TiCN；Cementedcarbides–usedintools；Fiber-reinforcedmetalsSiCreinforcedAl2O3ToolmaterialsFiberglassPolymerKevlarfibersinanepoxymatrixElemental(Carbon,Boron,etc.)Fiberreinforcedmetals；Autoparts；aerospaceRubberwithcarbon(tires);Boron,CarbonreinforcedplasticsMMC’SCMC’SPMC’SFormsofReinforcementPhaseFibersReinforcementsarenotnecessarilyintheformoflongfibers.Theycanbeparticles,whiskers,discontinuousfibers,sheetsetc.Agreatmajorityofmaterialsisstrongerandstifferinthefibrousformthaninanyotherform.Fibersusedinadvancedcompositeshaveveryhighstrengthandstiffnessbutlowdensity.TheyalsoshouldbeveryflexibleandhavehighaspectratioParticulatesmallparticlesthatimpededislocationmovement(inmetalcomposites)andstrengthensthematrixFlakesFibers-GlassMostwidelyusedfiber——piping,tanks,boats,sportinggoodsAdvantageslowcostCorrosionresistantLowcostrelativetoothercompositesDisadvantagesRelativelylowstrengthHighelongationModeratestrengthandweightTypes:Moisture↓strengthE-Glass-electrical,cheaperS-Glass-highstrengthFibers-kevlarCarbonandaramidfibersandprepregswereintroducedinthelatter1960s.Uses:highperformancereplacementforglassfiberExamplesArmor,protectiveclothing,industrial,sportinggoodsAdvantages:higherstrengthandlighterthanglassMoreductilethancarbonFibers-Carbon2ndmostwidelyusedfiberExamplesaerospace,sportinggoodsAdvantageshighstiffnessandstrengthLowdensityCarbonisaverylightelement.IntermediatecostTheabilitytotailortherequiredstiffnessandstrengthpropertiesofinternalboneplatesgivesthecarbonfibercompositesadefiniteadvantageovermetallicparts.Mostbiomedicalapplicationsareintheorthopedicmarket.Fibers-OthersBoronHighstiffness,veryhighcostLargediameter-200micronsGoodcompressivestrengthPolyethylene-tradename:SpectrafiberTextileindustryHighstrengthExtremelylightweightLowrangeoftemperatureusageCeramicFibers(andmatrices)Veryhightemperatureapplications(e.g.enginecomponents)Siliconcarbidefiber-inwhiskerform.CeramicmatrixsotemperatureresistanceisnotcompromisedInfrequentuseMetallicFibersMetallicfibers,suchassteelandtungsten,havehighstrengthsandshowveryconsistentproperties,unlikeceramicfibers.Sincedensityisveryhighforthesefibers,theyarerarelyusedtoreduceweightinacomposite.Drawingverythinmetallicfibers(lessthan100micron)isalsoveryexpensive.MatrixMaterialsFunctionsofthematrixTransmitforcebetweenfibersarrestcracksfromspreadingbetweenfibersdonotcarrymostoftheloadholdfibersinproperoreintationprotectfibersfromenvironmentmechanicalforcescancausecracksthatallowenvironmenttoaffectfibersDemandsonmatrixInterlaminarshearstrengthToughnessMoisture/environmentalresistanceTemperaturepropertiesCostMatrices–Polymeric：ThermosetscurebychemicalreactionIrreversibleExamplesPolyester:Mostcommon,lowercost,solventresistanceEpoxyresins:Superiorperformance,relativelycostlyMatrices–Polymeric：ThermoplasticsFormedbyheatingtoelevatedtemperatureatwhichsofteningoccursReversiblereactionCanbereformedand/orrepaired-notcommonLimitedintemperaturerangeto150℃Examples:Polypropylene…Matrices–OthersMetalMatrixComposites-highertemperaturee.g.,AluminumwithboronorcarbonfibersCeramicmatrixmaterials-veryhightemperatureFiberisusedtoaddtoughness,notnecessarilyhigherinstrengthandstiffness☆Notice:Compositepropertiesarelessthanthatofthefiberbecauseofdilutionbythematrixandtheneedtoorientfibersindifferentdirections.InterfaceTheinterfaceisaboundingsurfaceorzonewhereadiscontinuityoccurs,whetherphysical,mechanical,chemicaletc.Moreoftenthannot,theinterfacebetweenfiberandmatrixisratherrough,insteadofidealplanar.Thematrixmaterialmustwetthefiber.Couplingagentsarefrequentlyusedtoimprovewettabil