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外文翻译--超轻车辆设计 采用先进的汽车合成技术克服设计阻碍英文版.pdf

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外文翻译--超轻车辆设计 采用先进的汽车合成技术克服设计阻碍英文版.pdf

ULTRALIGHTHYBRIDVEHICLEDESIGNOVERCOMINGTHEBARRIERSTOUSINGADVANCEDCOMPOSITESINTHEAUTOMOTIVEINDUSTRY1.INTRODUCTIONAdvancedpolymericcompositeshaveseveraladvantagesincludingpartsconsolidation,highspecificstrengthandenergyabsorption,stylingflexibility,goodnoise/vibration/harshnessNVHcharacteristics,andexcellentcorrosionresistancethatsuitthemtoautomobiles.Furthermore,technologicaladvancesinprocessingandmaterialsappeartomakeadvancedcompositessuitableforhighvolumeapplicationslowpressurefabricationprocessessuchasresintransfermoldingRTMcouldrequireverylowinvestmentcostsand,dependingonthechoiceofresinandtoolingmaterial,offerfastcycletimes,whilenewversionsofresinsandfiberspromiselowcostandhighperformance.Inaddition,recentdevelopmentsinautomotivedesigndrivetheneedforwhatispotentiallyadvancedcompositesbiggestadvantagemassreduction.Ultralighthybridvehicledesigns,suchasRockyMountainInstituteshypercarconcept,necessitatestringentmassoptimizationparticularlyforthebodyinwhite1,theautomotivetermfortheunfinishedbodyanditsframeorchassis.Advancedcompositebodiesinwhitehavethepotentialtobeupto67lighterthanaconventionalsteelunibodyforequivalentsizeandsafety.However,aquicklookattheuseofadvancedcompositesintheautomotiveindustryraisesanobviousquestionIfadvancedcompositesaresuchwonderfulmaterials,whyaretheynotbeingusedAsidefromafewspecialtycomponentsfornichevehicles,suchasonepartintheDodgeViper,andevenfewerwholesystemapplicationssuchGMs1991Ultraliteconceptcar,theautoindustryhasshunnedtheuseofadvancedcomposites.Evenregularstructuralcomposites,usinglowperformancereinforcementsinquasiisotropicarrangements,arebeingappliedinlowerthanexpectedquantities.Inresponse,organizationstargetingtheautomotiveindustry,suchastheAutomotiveCompositesConsortiumACC,andcompositeproducers,includingsomeinNISTsAdvancedTechnologyProgramATP,areambitiouslyimplementingstrategiestospeedtheintegrationofstructuralandadvancedcompositesintotheautomobile.ButtheACCsfocusoncomponentapplicationssuchasacompositepickuptruckbox,liketheATPsfundingofmanufacturingprocessimprovementswithoutaccompanyingdesignchanges,indicateastrategyofevolutionaryintegration.Whileanevolutionaryapproachminimizesriskintheshortterm,itmaynotbetheoptimallongtermstrategytoovercomethebarrierstoputtingadvancedcompositesintocars.Justasthecombinationofanultralightbodywithahybriddrivelineprovidesaleapfrogapproachtoincreasingfuelefficiencyanddecreasingemissions,sothewholesystemapplicationofcompositestoanultralightmonocoqueBIWisthebestwayfortheadvancedmaterialsandautomotiveindustriestotunnelthroughthebarrierstolargescaleimplementation.Toanautomaker,aleapfrogapproachtocompositeintegrationcouldprovidebenefitsfaroutweighingtherisksanduncertaintiesofworkingwithunfamiliarmaterialsandtechnologies.Toanadvancedmaterialssupplier,aleapfrogapproachcanpreventthesetuptofailscenarioexperiencedinmanyautomotivecomponentapplicationsbyoptimallyexploitingthenewmaterialsintrinsicadvantages.Inaddition,aleapfrogapproachcouldpotentiallyexpandtheadvancedmaterialsmarketbyseveralfoldormore,achievingvolumeswhichcouldlowertheirproductscosts.ThusanadvancedmaterialspushintotheBIWshouldnotbesimplyanissueofmaterialsubstitutiononepartatatimeitneedstosubstitutematerialsusingawholeplatformdesignthatmaximizesthematerialsbenefitswhileminimizingandpotentially1eliminatingmanyoftheircosts.2.TECHNOLOGIESFORVOLUMEPRODUCTIONHowcouldpolymericcompositeBIWsbecompetitivelymadeinhighvolumeThereisnodefinitiveanswertheslateofpotentialtechnologiesforfabricatingandassemblinganadvancedmaterialsbasedBIWislargeandgrowingrapidly.Thediversityoftechnologicaloptionsaddsbothuncertaintyandrobustness.Also,whileadvancedpolymericcompositesrequiresophisticateddesigntotakeadvantageofuniquepropertiessuchasanisotropy,theirhighvolumemanufacturingandassemblytechniquesareconceptuallysimple.ThemostpromisingofftheshelforneartermtechnologiesforBIWmanufacturingarebrieflylistednextafullersurveyisin.2.1RawMaterialsPolymericcompositesincorporatefibrousreinforcementinaresinmatrix.Issuesimportantforrawmaterialselectionincludecost,compatibilitywithfabricationtechnologies,mechanicalandenvironmentalperformance,andrecyclability.2.2MoldingInthevariousmoldingoperations,theintermediatefiberformandresin,combinedeitherpreviouslyordirectlyinthemold,areshapedandhardenedintotheformofthemoldingcavity.ForanallcompositeBIW,liquidcompositemoldingLCMeitherresintransfermoldingRTMorstructuralreactioninjectionmoldingSRIMisgenerallyconsideredtobethemostpromisingprocess.BothRTMandSRIMutilizethermosetresinsbecauseoftheirlowviscosity,althoughcyclicthermoplasticsmaybeadaptable.LCMrequiresapreform,whichcancompriseavarietyofintermediatefiberforms.Asmentionedabove,anadvancedcompositeBIWwouldprobablyuseamorecomplexpreformwithhigherperformancefibers.Compressionmolding,normallydonewithSheetMoldingCompoundSMC,isahighpressureprocesswithalowercycletimeandgenerallyabettersurfacefinishthanLCM,suitingittoBIWapplicationswithinthecurrentsteelinfrastructure.However,likeglass,afullycompressionmoldedBIW,duetoitsweight,maynotbeabletoreapadequatesynergieswithahybriddrive,norhaveadequatecrashworthiness.BIWdesigns,lessmaturebuthigherperformancemanufacturingtechnologiessuchasRTMorSRIMappeartobemoreapplicabletoanallcompositeBIW.2.3TechnologicalBarriersUnliketheoveralldesignstrategyforcompositeBIWs,noneofthecompositetechnologieslistedaboverequirefundamentaladvancestopermitvolumeBIWmanufacturing.Eachneedsvaryingdegreesofrefinementbutseemstofacenointractabletechnologicalbarriersimplementationrequirestechnologyoptimizationandintegrationratherthaninvention.Someofthekeytechnoeconomicbarriersaredescribednext.2.3.1CarbonFiberCostThecostofcarbonfiberisoftencitedasthemostformidablebarriertocommercialapplicationsforcarbonfibercomposites.ForPANbasedcarbonfiber,thecombinationofexpensiveprecursorandlowvolume,specializedequipmenthasledtoitshighcost.However,twoenterprisingdomesticmanufacturers,ZoltekandAkzoNobel,offerlowcost,hightowcommoditygradecarbonfiber.Bulkcreelpricesfortheircontinuousfiberarecurrentlyaslowas17.60/kg.Centraltofurtherdecreasesinpricearecheaperversionsoftheprecursor,whichhasnocostcontrollingdifferencesfromthecommoditygradeacrylicfiberthatcosts3.00/kg.toproduce.Inaddition,highervolumesofproductionareneededtolowerunitcapitalandlaborcosts.HighvolumemanufacturingcouldsoonberealizedZoltekandAkzoplanneartermexpansion.Theirstrategycouldovercomethecostbarrierforadvanced2compositeswithasupplypushoflowcostfiberintothetransportationmarket.2.3.2PreformingThedifficultyofproducingcomplexpreformsatreasonablecostiscitedalmostasoftenascarbonfibercostasthechieftechnicalbarriertohighvolumeadvancedcompositesmanufacturing.PrincetonsConferenceonBasicResearchNeedsforVehiclesoftheFuturerecentlygavepreformingthehighestpriorityamongneededresearchandinnovation.Currently,automakersfavorquasiisotropicchoppedorcontinuousmatpreformsofglassfiber,which,aswasmentionedabove,aretooweak,isotropic,andhenceheavyforamassoptimizedBIW.Theanisotropicstrategiescommoninaerospaceapplications,suchasprepregtapesandhandlayupwithautoclaving,aretooslowandcostlyforcars.Fortunately,theproblemofcreatinglowcostcomplexpreformsmaynotbeintractableseveralinnovativetechnologiescouldpermittherapidandinexpensivefabricationofcomplex,netshapepreforms.FabricssuchasCOTECHarenoncrimp,stitchbondedlayersofunidirectionalcontinuousfiberthat,accordingtotheirmanufacturer,canbecheaperthanrandommatyetperformaboutaswellasunidirectionaltape.Astitchbondingprocesscaninexpensivelycreatecomplexpreformsbycombiningaquasiisotropicbaseoffabricwithstrategicallyplacedinsertsofunidirectionalfabricorrovingatmaximumloadpoints.Alternatively,theCompFormprocessclaimsevencheaperandfastercomplexpreformingpotential,substitutingUVcurablebindersforfabricstitchesalthoughthisprocesscannotbeusedwithacarbonintensivepreform.Forcreatingnetshapepreforms,fastultrasoniccutting,usingnestingpatternstominimizewaste,couldbeagoodcomplementtostitchbonding.Obviously,complexpreformsrequireheavyfrontendengineeringtoavoidresinflowproblemssuchasracetrackingandunexpectedfibermovements.Nevertheless,theseprocesseshaverealworldvaliditybothUVstitchingandultrasoniccuttingwereusedtocreateacomplexpreformforaBuickRivierabumperbeam.2.3.4SurfaceQualityBecausecompositemonocoquesrequirestructuralcompositeswithClassAsurfaces,asignificantbarrierisproducingcomponentswithbothhighfibervolumefractionsandsmooth,porosityfreeexteriors.IfsofttoolingisusedtocapturestrategicadvantagesortoensurecompatibilitywithEbeamcuringforcycletimereductions,thechallengeofobtainingClassAsurfacesbecomesmorecomplexandimportant.WhileClassAsurfacescouldbedifficultforstructuralcomposites,theyarebynomeansimpossible.Thestitchbondedfabricdescribedaboveforcomplexpreformswetsouteasilyandhasasurprisinglysmoothsurface,asitismadeupofunidirectionallayers,sosubjecttoresinconsistencyandtoolingsurfacequality,itcouldsimplybesurfacefinishedwithaClassAmoldandpainted,savingtheinvestmentandoperationcostsofconventionalsteelfinishingprerequisitetopaintingexteriorBIWparts.AnevensimplerapproachcouldalsoavoidpaintingbyapplyingoneofseveralproprietarylayinthemoldClassAcolorcoatpolymerproducts,orperhapsinjectathermoplasticcolorcoatintoaClassAmoldandthenlayinthestructuralelementsbehinditusingacompatibleresinsystem.3.OVERCOMINGTHEBARRIERSTheresultsofthesesurveysledonesetofinterviewerstoconcludethatsincetheadoptionofstructuralcompositesfacesmultiplebarriers,noonesimplequickfixwillrapidlyacceleratetheirdeployment.Yetdespitecompleximplementationdetails,thereisarelativelysimpleifunexpectedconceptualframeworktointegrateadvancedcompositesintoautomaking.Themosteffectivewaytoovercomethebarriersappearstobereplacingtodaysdominantstrategyofincremental,partbypartmaterialssubstitutionwithawholesystemdesigned,alladvancedcompositeBIW.Thisleapfrogapproachintegratesacleansheetdesign,highperformancerawmaterials,3existingmanufacturingmethods,andaradicallysimplerandsmallerassemblyprocess.Itholdspromiseofbypassingmanybarriersandofchangingautomakersattitudetowardadvancedcompositesfromanecessaryevilorindefinitelypostponableinconvenienceintoapromptandlucrativeopportunity.Waystocircumventmajorbarriersaresurveyednext.3.1CostComponentbycomponentsubstitutionofcompositesforsteelcannotoccuruntilmarketdeterminedmaterialpricesjustifysubstitutiononasinglepartbasis,eitherthroughcheapermanufacturingorthroughsavedgasoline,withlittleifanycreditformassdecompoundingandevenforthesavedsteelitself.Thesubstitutedmaterialsremaincostly,however,becauseonlysmallvolumesarebeingbought.Creditshouldbe,butisnotalways,takenforthemodestreductionsinpartscountasaresult,thinkingincomponenttermsmakesithardorimpossibletoquantifysavedassemblycosts.Finally,integrationofacompositecomponentwithinasteelBIWcanraiseoverallassemblycosts,especiallyifthecompositepartscycletimesarelongerortheirdimensionsandotherpropertiesaremorevariable.Asaresult,integrationrequirementsofteneconomicallyfavorcompressionmoldingoverRTM,leadingtopartswithsuboptimalperformancefordemandingstructuralapplications.Incontrast,cleansheetwholeplatformredesigncanyieldradicalreductionsinpartscount,size,andcomplexitythetypicalBIWwouldhaveonlyafewparts,andassemblyeffortwoulddropbyanorderofmagnitude.Buyingthespecialmaterialsinbulkshouldyielddiscountsand,throughincreasingproductionvolumes,cutmarketprices.Productionvolumescouldbeoptimizedforconvenienceandmarketdemand,ratherthanartificiallyinflatedtomeetamortizationrequirementsforsteeltoolsandpresses.Productionflexibilitycouldberetainednotonlyinvolumebutalsoinstyling.Finally,savingscouldaccumulatedownstreamfromBIWmanufacturingthroughamuchsmallerandsimplerdrivelineandothercomponents,shorterproductcycletimes,andgreaterproductionflexibility.3.2SafetyAdvancedcompositeshavefundamentallydifferentenergyabsorptioncharacteristicsandfailuremodesthansteel.Theyfituncomfortablyintothetraditionalsafetydesignparadigm,especiallywhenappliedbysteelorienteddesignerswhotreatadvancedcompositesasblacksteel.Inadequateredesigncanyieldsuspectcompositeparts,creatinganimpressionofpoorsafety.However,cleansheetdesignofanallcompositeBIWcantakeadvantageofthesematerialsuniqueproperties,including,inpropershapes,specificenergyabsorptionfivetimesthatofsteel.Equivalentsafetyforanultralight,usingsuperiormaterialsanddesigntocompensateforlightmass,requiresanewdesignapproachimplementableonlyatthesystemlevel,notinisolatedcomponentsalone.ToexplicatethedesignparadigmforanallcompositeBIW,RMIiscurrentlypreparingaprimeronultralightcompositebasedcarsafetyprinciplesandpraxis.3.3RiskLesswidelyperceivedthantheriskofleapfroggingtoanallcompositeBIWistheinherentandoftenruinousriskofthepresentBIWmanufacturinginfrastructure.Itsinherentlyhighfixedcostsandlowvariablecostsmakeprofitsextremelysensitivetosalesvolumes,endangeringincomewheneverdemandfalters.Furthermore,thehighfixedcostsimpellargeproductionruns,whichshrinkmodelvarietyandfocusmoreriskonthemarketsuccessofeachmodel.Longproductcycles,too,makenewmodelslagbehinddynamicpublictastes,furtherheighteningtheriskofdisastrousventures.Conventionalcomponentbaseduseofcomposites,forcedintothesameparadigm,couldcarrysimilarrisks.Incontrast,softtooled,netshapeadvancedcompositemonocoquescouldofferstrategicadvantageswithapreciselyoppositeriskprofile.Thetoolingcouldbecheaplyfabricatedwithfewparts,

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