复合材料定义

2020/5/181复合材料定义•复合材料是由两种或两种以上物理和化学性质不同的物质组合而成的一种多相固体材料。•在复合材料中，通常有一相为连续相，称为基体；另一相为分散相，称为增强材料。两相之间存在着相界面。•虽然复合材料的组分材料保持着其相对的独立性，但其性能却不是组分材料性能的简单相加，而是相互“取长补短”，有着协同作用，极大的弥补了单一材料的缺点。在一定程度上讲，它综合了各种材料如纤维，树脂，橡胶，金属，陶瓷等的优点。Advantagesofcompositematerials•材料性能指标的自由设计性•材料与结构的一致性•产品型体设计的自由性2020/5/183复合材料的主要优点•比强度，比模量大（以碳纤维，硼纤维及有机纤维增强的聚合物基复合材料的比强度相当于钛合金的3－5倍，比模量相当于金属的4倍之多）•耐疲劳性能好（聚合物基复合材料中纤维与基体的界面有能阻止材料受力所致的裂纹扩展的效果）•减震性好（一是由于其具有高的自振频率，二是由于复合材料的界面具有吸振能力，使材料的震动阻尼很高）•过载时安全性好（当过载时，一部分纤维断裂，载荷会迅速重新分配到未破坏的纤维上）•有很好的加工工艺性（有多种加工工艺如手糊成型，模压成型，挤拉成型等）复合材料的分类•按基体材料分主要有:1.聚合物基复合材料2.金属基复合材料3.无机非金属基复合材料（包括陶瓷基和水泥基复合材料的分类•按增强纤维种类分主要有1.玻璃纤维复合材料2.碳纤维复合材料3.有机纤维复合材料（包括芳香族聚酰胺纤维，芳香族聚酯纤维和高强度聚烯纤维等）4.金属纤维5.陶瓷纤维2020/5/186聚合物基体的作用•把增强纤维粘在一起•分配增强纤维间的载荷•保护增强纤维不受环境的影响2020/5/187聚合物基体•常用作基体的聚合物–不饱和聚酯树脂，–环氧树脂，–酚醛树脂–耐高温树脂–热塑性聚合物•辅助材料：固化剂，增韧剂，稀释剂，催化剂等复合材料的界面•复合材料界面的重要性•复合材料界面的理论•复合材料界面的表征•纤维表面处理增强纤维表面改性•气相氧化法（DryGaseousOxidation）•液相氧化法（WetChemicalOxidation）•化学偶联剂处理法（ChemicalCoupling）•聚合物涂层法（PolymerCoating）•（涂覆）沉积法（Deposition）•电聚合与电沉积法•化学接枝聚合法（ChemicalGrafting）•等离子体处理方法（Plasma）Applicationofcomposites•Seecompositematerials1复合材料成型•Handlay-upmolding•Spray-upmolding•RTM(Resintransfermolding)•RIM(Reactioninjectionmolding)•Resininfusion•Sheetmoldingcompound•Bulkmoldingcompound•Filamentwinding•Pultrusion•LFRTPHandlay-upmoldingHandlay-upmouldingmaybeusedfortheproductionofpartsofanydimensions,forexample,technicalpartsofafewtensofm²area,aswellasswimmingpoolsof150m²developedarea.But,thismethodisgenerallylimitedtothemanufactureofpartswithrelativelysimpleshapes,requiringonlyonefacetohaveasmoothappearance(theotherfacebeingroughfromthemouldingoperation).Itisrecommendedforsmallandmediumvolumes,forwhichtheinvestmentinmouldsandequipmentshouldnotbeveryhigh.Handlay-upmouldingThecontactmouldingmethodconsistsofapplyingsuccessivelyontoamouldsurface:-areleaseagent-agelcoat-alayerofliquidthermosettingresin,ofviscositybetween0.3and0.4Pa.s,andofmediumreactivity-alayerofreinforcement(glass,aramid,carbonetc.)intheformofchoppedstrandmatorwovenrovingandtoimpregnatethereinforcementbyhandwiththeaidofarollerorabrush.Thisoperationisrepeatedasmanytimesastherearelayersofreinforcement,inordertoobtainthedesiredthicknessofthestructure.Spray-upmouldingSpray-upmouldingisderivedfromhandlay-upmoulding,andisparticularlysuitedtopartsofmediumtolargedimensionsandsimpleshapes.Partsproducedbyspray-uparepleasureboathulls,swimmingpools,covers,endcapsoflargediametertanks,reinforcedacrylicbathtubsetc.Productivityisbettercomparedtohandlay-upmoulding.Spray-upmouldingTheprocessconsistsofsimultaneouslysprayingontothemould,choppedglassstrands,normallyof30mmlength,andtheresinnecessaryfortheirimpregnation.Aftersprayingontothemould,rollingbyhandisnecessarytoflattenorcompacttheglass-resinmixturewellontothemouldsurfaceand,asfaraspossible,eliminateairbubblesgeneratedbythesprayingsystem.Thespraymachinegenerallyconsistsof-aglasschopperdrivenbycompressedair,-apneumaticpumpforfeedingresintothespraygun,-Asolventdeliverysystemforcleaningthegun.RTMRTMallowsthemouldingofcomponentswithcomplexshapeandlargesurfaceareawithagoodsurfacefinishonbothsides.Theprocessissuitedforshortandmediumproductionrunsandisemployedformanydifferenttransportapplications(truckcabsareanexample).RTMThisprocessconsistsoffillingarigidandclosedmouldcavitybyinjectingaresinthroughone,orseveral,points,dependingonthesizeofthecomponent.Thereinforcementsarepreviouslyplacedintheinteriorofthemould,beforeclosingandlockingitfirmly.Usually,polyesters,epoxy,phenolic&acrylicresinsareused,andtheycanbefilledifneeded.Differenttypesofmouldcanbeused,dependingontherequiredproductionrate:Heatcanbeappliedtothemouldtoshortenthecure-time,inwhichcasesteelmouldsmaybenecessary.Lowprofileresinscanbeemployedwithheatedmouldstoimprovethesurfacefinishandappearanceofthemouldedpart.Alternatively,lowpressureRTMallowslowercost,compositetoolingtobeusedwithlowtonnagepresses.Thereinforcementsmaybecontinuousfilamentmats,complexesorfabrics,butgenerallycontinuousfilamentmatsarethemostwidelyused.Theuseofpreformsfromcontinuousstrandmatspermitsaconsiderableincreaseinproductionratetobeachieved.ReactionInjectionMoldingTheRIMprocessisbasedontheinjectionofthetwopolyurethanecomponents(apolyolandanisocyanate)insideamouldcavity.Theautomotivemarketoffersthemostimportantapplicationsforthisprocess,suchasdashboards,interiorpanelsandunderbodyshields.ManytruckcomponentsarealsomanufacturedbyRIM,suchasbumper-beams,front-endsandgrills.RIMTheprincipleofRIMconsistsofinjectingintoaclosedmouldandunderlowpressure(0.5MPa),twoormorereactivecomponentsmixedwithinanozzle,justpriortotheirinjectionintothemould.Thereaction,inthecaseofapolyolandanisocyanate,leadstotheformationofapolyurethane.Theintroductionofshortstrands,suchasmilledfibres,directlyintooneofthetworeactiveconstituents,leadstotheinjectionofapre-reinforcedmixture.ThisisknownasR-RIM[ReinforcedReactionInjectionMoulding].Theintroductionoflongstrandreinforcements-suchascontinuousfilamentmats,fabrics,complexesorchoppedstrandpreforms-intothemouldbeforetheinjectiontakesplace,al