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外文翻译--在树脂传递模塑成型过程中织物结构和模具曲率对预制物的渗透性以及注入模具时所产生的影响 英文版.pdf

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外文翻译--在树脂传递模塑成型过程中织物结构和模具曲率对预制物的渗透性以及注入模具时所产生的影响 英文版.pdf

FabricstructureandmoldcurvatureeffectsonpreformpermeabilityandmoldfillingintheRTMprocess.PartI.ExperimentsS.Bickerton,E.M.Sozer,P.J.Graham,S.G.AdvaniDepartmentofMechanicalEngineering,UniversityofDelaware,Newark,DE19716,USAReceived15October1998receivedinrevisedform31August1999accepted23September1999AbstractLiquidcompositemoldingLCMprocessesrequiretheimpregnationofapolymericresinthroughaporouspreform,beingcomposedofglass,carbon,orkevlarfibers.Thesuccessfulmanufactureofcompositepartsthroughthesemethodsisdependentonthesuccessfulfillingofthemoldcavity,expellingallairfromwithin.Numericalsimulationsarebeingdevelopedtomodelthisprocess,andarepowerfulmolddesigntools.Theaccuracyofsuchsimulationsisstronglydependentonthespecificationofthepreformpermeabilitytensorthroughoutthemoldcavity,beinganumericaldescriptionoftheresistancetoresinflow.Changesinpreformarchitecturecaneasilymodifylocalpermeability,andhencethemoldfilling.Cornersinmoldcavitiesareapotentialsitesforpreformdeformation,andarethefocusofthisstudy.Afamilyoffivemoldshavebeenstudied,containingcornerradiifrom0.06to8.0in.Adetailedflowvisualizationstudyhasbeencompletedtoinvestigatetheinfluenceofmoldcornerradiionflowfrontprogressionandinjectionpressure.Whileflowfrontprogressionwasnotsignificantlyaffectedbydifferentcornerradii,injectionpressureswerefoundtobegreaterforthemoldswithsmallercornerradii.Actualcompositepartsmanufacturedinthesamemoldshaverevealedthatthemoldsarenotofconstantcavitythickness,aswastheoriginalgoal.Todeterminetheimportanceofcornerradiionmoldfilling,itwillbenecessarytoseparatetheeffectsofinplanepreformcompressionfromanyeffectduetocorners.Toaccomplishthisgoal,theexperimentaldatapresentedhereisbeingcomparedwithdetailednumericalstudies,whichwillbepresentedinpartIIofthiswork.KeywordsLiquidcompositemoldingE.Resintransfermolding1.IntroductionLiquidcompositemoldingLCMprocessesarepopularcompositematerialmanufacturingtechniquesgainingfavorinthecivil,aerospace,automotiveanddefenseindustries.Theseprocessespossessseveraladvantages,includingnetshapeproduction,relativelylowinjectionpressures,moderatelylowcycletimes,andsimpletoolingrequirements.LCMprocesseshavethepotentialtoproducelowcost,highquality,geometricallycomplexcompositeparts.ResintransfermoldingRTM,structuralreactioninjectionmoldingSRIM,SeemancompositeresininfusionmoldingprocessSCRIMP,andinjection–compressionmoldingareexamplesofthemanyLCMprocessvariations.Generally,LCMprocessescanbedescribedasfollows.First,thefiberpreformismanufactured,beingthereinforcementoftheintendedpart.OneofthemajoradvantagesofLCMprocessesistheabilitytotailorthepreformexactlytotheneedsofthepart,placingreinforcementasrequired.Fiberpreformsareconstructedfromawidevarietyofarchitectures,constructedfromglass,carbonorkevlarfibers.Thefiberpreformwillprovidethefinishedpiecewiththemajorityofitsstructuralproperties.Thepreformisplacedwithinthemoldcavity,andthemoldissealed.Next,thepolymericresinisinjectedintothemoldcavity,saturatingthepreformandexpellinganyairpresent.Acuringreactionisinitiated,eitheraftercompletelyfillingthemoldcavity,orpossiblyatsomestageduringimpregnation.Afterthepieceissufficientlycured,thefinishedcompositeproductcanberemovedfromthemold1.ThesuccessfulmanufactureofLCMpartsissensitivetothepreforming,impregnation,andcuringstages.Thispaperwillfocusonthedeformationofpreformsaroundcornerswithinmolds,studyingitsinfluenceonthesubsequentimpregnationstage.Defectsincurredthroughunsuccessfulmoldfillingincludebothmicroscopicandmacroscopicvoids2,3.Microscopicvoidsrefertotinyairbubblestrappedwithin,andaroundfiberbundlesofthepreform.Suchvoidsareoftenverydifficulttoeradicatecompletely,butattemptsshouldbemadetominimizethem4.MacroscopicvoidsrefertolargeairpocketsthathavebeentrappedwithinthemoldcavityduetoafaultyinjectionschemeCompositesPartA312000423–438Correspondingauthor.e.g.incorrectlyplacedinjectionportsandvents.Usuallysuchvoidswillresultinapartthatisunusable,asportionsofthepartwillbeformedbydrypreformhavingnostructuralrigidity.Theaimofthisworkwastoinvestigatewhethercornersofdifferentradiiwouldhaveanysignificanteffectontheprogressoftheresinflowfrontwithinamoldcavity,andpossiblycausetheformationofmacroscopicvoids.LCMfillingprocessesaretypicallymodelednumericallyusingDarcyslaw,whichrelatespressuregradientswithinamoldtoanumericalmeasureoftheresistancetoflowthroughthepreform,beingthepermeability.Inrecenttimes,muchefforthasbeenplacedintothedevelopmentofDarcyslawbasednumericalprocesssimulationsofLCMfillingprocesses5–11.Suchsimulationscanpredicttheflowpatternsandpressuredistributionaslongaswehavepriorknowledgeofthematerialparameters,beingprimarilythecomponentsofthepermeabilitytensor.ManypapershavebeenpublishedconcerningpermeabilityS.Bickertonetal./CompositesPartA312000423–438424abFig.1.MoldAaaluminumbasebaluminumbaseandacrylictop.measurements,andanalyticalpermeabilitypredictions12–15.Thoughmuchprogresshasbeenmadeinbothfields,thewidevarietyofpreformstyles,andtheirvariationinarchitecturewithcompaction,haveinhibitedtheformationofacomprehensivepermeabilitydatabase.Preformpermeabilitiescanalsobefurtheralteredbyseveralsecondaryeffects,includingracetracking16,17,multilayeredpreforms18,preformcompaction19,andpreformshearing17,20,amongothers.ThisworkhasaimedtodeterminethemagnitudeofeffectonLCMmoldfillingprocessesduetomoldcornersofvariousradii.Ifanyeffectsduetomoldcornersaresignificant,modelsneedtobedevelopedtoaccountforanyvariationinpermeabilityintheseregions.Iftheeffectsareshowntobenegligible,permeabilitytensorsdeterminedforflatportionsofamoldwiththesamefibervolumefractioncanbeappliedtothesecornerregions.PreliminarystudiesintotheflowaroundcornershasbeenpresentedbyFriedmanetal.21.Verydetailedexperimentsandcalculationshavebeenpreformed,however,theevidencepresenteddoesnotclearlydemonstratethemagnitudeofanyeffectsduetomoldcorners.Theexperimentalportionofthisstudyhasbeencompletedintwoparts.Detailedflowvisualizationexperimentshavebeencompletedtodeterminethenatureandmagnitudeofeffectcornersofvariousradiihaveonthemoldfillingprocess.Fivemoldswereused,havingmoldradiivaryingfrom0.06to8.0in.Thefemalehalvesofthemoldsweremachinedfromacrylic,allowingforthemoldfillingtobevisualized.Threedifferentpreformstyleswereinvestigated,atavarietyoffibervolumefractions.Injectionpressurehistoriesandflowfrontprogressionhavebeenrecorded.Thesecondportionoftheexperimentalprogramhasfocusedonthemanufactureofactualcompositepiecesinthesamemolds.Somesmallmodificationsweremadetothemolds,inordertoprotecttheacrylicmoldhalvesfromtheresinused.Partsweremanufacturedusingthesamepreformsusedintheflowvisualizationstudy.Thesepartshaveservedtwopurposes,verifyingthegeometryofthemoldcavities,andprovidingsomeinsightintothestateofpreformdeformationnearcorners.ThefindingsofourexperimentalstudiesarepresentedinS.Bickertonetal./CompositesPartA312000423–438425VentsPortInjectionStiffeningBarsFig.2.Overheadviewofassembledmold,withstiffeningbars.Fig.3.SchematicdefiningmoldgeometricaldataamoldsA–DbmoldE.Table1MoldgeometricaldataR1m/in.R2m/in.T1m/in.T2m/in.MoldA1524£10230.0604699£10230.1853048£10230.1202235£10230.088MoldB2540£10230.1005715£10230.2252997£10230.1182159£10230.085MoldC6350£10230.2509525£10230.3753023£10230.1192159£10230.085MoldD1270£10230.5001588£10230.6252997£10230.1183023£10230.119MoldE2032£10238.0002064£10238.1253073£10230.121–thispaper.Duetotheactualmoldcavitygeometries,twotypesofpreformdeformationhavebeenintroduced.Astwoofthemoldcavitieshaveportionswithsignificantlydifferentthicknesses,effectsduetopreformcompressionhavebeenidentified,andarecoupledwiththosethatmaybepresentduetocornerradii.Afollowuppaperwillpresentadetailednumericalstudythatwillservetoidentifytheinfluenceofbothdeformationstyles.ThisisneededtoassesstheimportanceofmoldcornerradiionLCMfillingprocesses.2.ExperimentalprogramDetailedflowvisualizationexperimentshavebeenperformed,providingextensivevalidificationdataforthenumericalsimulationswhicharepresentedinoursecondpaper.Experimentallymeasuredinjectionpressurehistorieswillbepresentedforthreepreformstyles,andatvariousvolumefractions.Videosnapshotsareprovidedfromselectedexperiments.Themolds,beingdesignedforflowvisualization,havebeenmodifiedtoallowthemanufactureofactualcompositeparts,usingthesamepreforms,andavinylesterresin.Thesepartshavebeenanalyzedtoprovidedetailedinformationaboutthemoldsused,theirarchitectureandvolumefraction,whichshedslightonhowfabricscompactaroundcurvatures.2.1.MolddetailsAfamilyoffiveRTMflowvisualizationmoldsweremadeavailableforthisstudybytheUSArmyResearchOffice.Thesemoldswereinitiallydesignedwiththeintenttostudytheeffectofcornersonthemoldfillingprocess,thecornerradiibeingdifferentineachmold.Bymanufacturingcompositepartswithinthesemoldsdetailedmoldcavitydimensionswereobtained.Itwasfoundthatthreeoutofthefivemoldsdidnothaveconstantcavitythicknesses,andweresignificantlydifferentfromthehorizontaltotheinclinedflatsectionsofthemold.Bothradiusandthicknessdataispresentedinthissection.Moldcavitythicknessvariesfromonesectiontoanotherinamold,andalsofromonemoldtoanother.HencethisrequirestheS.Bickertonetal./CompositesPartA312000423–438426Fig.4.Experimentalschematicforflowvisualization.Fig.5.Schematicofmoldconfigurationforcompositepartmanufacture.

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