外文翻译碳纤维增强塑料的铣削破坏和尺寸精度设计实验.doc

Damageanddimensionalprecisiononmillingcarbonfiber-reinforcedplasticsusingdesignexperimentsJ.PauloDavim,PedroReisDepartmentofMechanicalEngineering,UniversityofAveiro,CampusSantiago,3810-193Aveiro,PortugalReceived24June2002；receivedinrevisedform10May2004；accepted8June2004AbstractMillingcompositematerialsisarathercomplextaskowingtoitsheterogeneityandthenumberofproblems,suchassurfacedelamination,thatappearduringthemachiningprocess,associatedwiththecharacteristicsofthematerialandthecuttingparameters.Withthepurposeofunderstandingandreducingtheseproblems,thispaperpresentsastudythatevaluatesthecuttingparameters(cuttingvelocityandfeedrate)underthesurfaceroughness,anddamageinmillinglaminateplatesofcarbonfiber-reinforcedplastics(CFRPs).Aplanofexperiments,basedontheTaguchismethod,wasestablishedconsideringmillingwithprefixedcuttingparametersinanautoclaveCFRPcompositematerial.Ananalysisofvariance(ANOVA)wasperformedtoinvestigatethecuttingcharacteristicsofCFRPcompositematerialusingcementedcarbide(K10)endmills.TheobjectivewastoestablishamodelusingmultipleregressionanalysisbetweencuttingvelocityandfeedratewiththesurfaceroughnessanddamageinaCFRPcompositematerial.©2004ElsevierB.V.Allrightsreserved.Keywords:Milling；Carbonfiber-reinforcedplastics(CFRPs)；Dimensionalprecision；Taguchismethod；Orthogonalarrays；Analysisofvariance(ANOVA)1.Introduction1.1.Millingfiber-reinforcedplastics(FRPs)Millingisthemachiningoperationmostfrequentlyusedinmanufacturingpartsoffiber-reinforcedplastics,becausecomponentsmadeofcompositematerialsarecommonlyproducedbynet-shapethatoftenrequiretheremovalofexcessmaterialtocontroltolerances,andmillingisusedasacorrectiveoperationtoproduceawelldefinedandhighqualitysurfaces1.Themachinabilityoffiber-reinforcedplasticsisstronglyinfluencedbythetypeoffiberembeddedinthecompositeandbyitsproperties.MechanicalandthermalpropertieshaveanextremelyimportanceonmachiningFRP.Thefiberusedinthecompositeshasagreaterinfluenceintheselectionofcuttingtools(cuttingedgematerialandgeometry)andmachiningparameters.Itisfundamentaltoensurethatthetoolselectedissuitableforthematerial.Theknowledgeofcuttingmechanismsisindispensableinviewofcuttingmechanicsandmachinabilityassessmentinmilling1,2.Compositematerialssuchascarbonfiber-reinforcedplastics(CFRPs)madebyusingcarbonfibersforreinforcingplasticresinmatrices,suchasepoxy,arecharacterisedbyhavingexcellentpropertiesaslightweight,highstrengthandhighstiffness.Thesepropertiesmakethemespeciallyattractiveforaerospaceapplications2.Surfaceroughnessisaparameterthathasagreaterinfluenceondimensionalprecision,performanceofmechanicalpiecesandonproductioncosts.Forthesereasons,researchdevelopmentshavebeencarriedoutwiththepurposeofoptimisingthecuttingconditionstoreachaspecificsurfaceroughness3,4.Forachievingthedesiredqualityofthemachinedsurface,itisnecessarytounderstandthemechanismsofmaterialremoval,thekineticsofmachiningprocessesaffectingtheperformanceofthecuttingtools5.Theworksofanumberofauthors612,whenreportingonmillingofFRP,haveshownthatthetypeandorientationofthefiber,cuttingparametersandtoolgeometryhaveanessentialpaperonthemachinability.EverstineandRogers6presentedthefirsttheoreticalworkonthemachiningofFRPsin1971,sincethentheresearchmadeinthisareahasbeenbasedonexperimentalinvestigations.Koplevetal.7,Kaneeda8andPuwandHocheng9concludedthattheprincipalcuttingmechanismscorrelatestronglytofiberarrangementandtoolgeometry.Santhanakrishmanetal.10andRamuluetal.11carriedoutastudyonmachiningofpolymericcompositesandconcludedthatanincreasingofthecuttingspeedleadstoabettersurfacefinish.Hochengetal.12studiedtheeffectofthefiberorientationonthecutquality,cuttingforcesandtoolwearonthemachinability.Insummary,itcanbenoticedthattheworkscarriedoutonthemachinabilityofFRP,arebasicallyrelatedonthewearofcuttingtoolsandthequalityonthesurfaces,asafunctionofthecuttingconditions,thedistributionofstaplefibersinthepolymericmatrixandtheangleofinclinationofstaplefibers.Thecurrentpaperinvestigatestheinfluenceofcuttingparameters(cuttingvelocityandfeedrate)onthesurfaceroughness(Ra),delaminationfactor(Fd),andinternationaldimensionalprecision(IT),onCFRPcompositematerialusingcementedcarbideendmills,withthepurposetoestablishaempiricalrelationshipbetweencuttingparameters(Vandf)andsurfaceroughness(Ra)anddelaminationfactor(Fd).1.2.AutoclaveprocessTheautoclaveprocessiswidelyusedtoproducehigh-performancelaminatesusuallywithfibersreinforcedepoxysystems.Compositematerialsmanufacturedbyautoclaveareparticularlyimportantforaerospaceapplications.Thisprocessusesapressurisedvesseltoapplypressureandheattobothpartsthathavebeensealedinavacuumbag.Nextitcanbeseentheseveralstagesofthisprocess.Onthefirststage,theprepregcarbon-fiberepoxymaterialiscarefullylaidoutonatabletoensurethatfiberorientationmeetsthedesignrequirement,wheretheprepregmaterialconsistsofunidirectionallongcarbonfibersinapartiallycuredepoxymatrix.Onthesecondstage,piecesoftheprepregmaterialarecutoutandplacedontopofeachotheronashapedtooltoformalaminate.Thelayerscouldbeplacedindifferentdirectionstoproducethedesiredstrengthpatternsincethehigheststrengthofeachlayerisindirectionparalleltothefibers.Aftertherequirednumberoflayershasbeenproperlyplaced,thetoolingandtheattachedlaminatearevacuum-bagged,forremovingtheentrappedairfromthelaminatedpart.Finally,thevacuumbagandthetoolingisputintoanautoclaveforthefinalcuringoftheepoxyresin.Afterremovedfromtheautoclave,thecompositematerialisreadyforfurtherfinishingoperations2,13.2.Experimentalprocedure2.1.MethodandmaterialsInordertoreachtheobjectiveofthisexperimentalwork,mainlytheestablishmentofthecorrelationsbetweencuttingparameters(Vandf)andsurfaceroughness(Ra)anddelaminationfactor(Fd),machiningissueswereperformedunderdifferentcuttingconditionsontheCFRPcompositematerial.Thecompositematerialusedinthetests(epoxymatrixreinforcedwith55%ofcarbonfiber),suppliedbyINEGI,wasproducedbyautoclavewithafiberorientationof0/90,ascanbeobservedinFig.1.Theexperimentshavebeencarriedoutinalaminateplate,madeupwith16alternatinglayersoffiberswith4mmofthickness,usingtwocementedcarbide(K10)endmills,presentedinFig.2,with6mmofdiameter.Bothcementedcarbideendmills,two-flute(R216.32-06030-AC10P-1020)andsix-flute(CCT-GSR-D0635),weremanufacturedaccordingtoISO.Thetwo-fluteendmillpresentsthefollowinggeometry:ahelixangleof30,arakeangleof1030_,aclearanceangleof9andaflutelengthof10mm.Thesix-fluteendmillpresentsaneutralhelixand20mmofflutelength.ThedepthofthecutonCFRPcompositematerialwas2mm.Amillingmachine“LC-11/2VSFirst”with2.2kWspindlepowerandamaximumspindlespeedof2500rpmwasusedtoperformtheexperiments.Thefixationofthecompositematerial(plate)wasmadeasobservedinFig.3,tomakesurethatvibrationsanddisplacementdidnotexist.Thesurfaceroughnesswasevaluated(accordingtoISO4287/1)withaHommeltesterT1000profilometer,ascanbeobservedinFig.4.Foreachtestfivemeasurementsweremadeovermillingsurfaces,accordingtoFig.5.Consideringthenumberofmeasurementstobecarriedout,aprogrammabletechniquewasused,bypreviouslyselectingaroughnessprofile,thecut-off(0.8mm)andtheroughnessevaluatorparameter(Ra)accordingtoISO.Dataacquisitionsweremadethroughpro-filometer,byinterfaceRS-232toPCusingthesoftwareHommeltesterTurbo-Datawin.Thedamagecausedonthecompositematerialwasmeasuredwithashopmicroscope,MitutoyoTM500®,with30×magnificationand1_mresolution.2.2.PlanofexperimentsTaguchismethodhasbeenwidelyusedinengineeringanalysisandconsistsofaplanofexperimentswiththeobjectiveofacquiringdatainacontrolledway,inordertoobtaininformationaboutthebehaviourofagivenprocess.TheTaguchismethodfortwofactorsatthreelevelswasusedfortheelaborationoftheplanofexperiments.Table1indicatesthefactorsstudiedandtheassignmentofthecorrespondinglevels.Bylevelsismeantthevaluestakenbythefactors.TheorthogonalarrayL9(24),wasselectedasshowninTable2,whichhasninerowscorrespondingtothenumberoftests(8degreesoffreedom)withtwocolumnsatthreelevels.Thefactorsandtheinteractionsareassignedtothecolumns.Theplanofexperimentswasmadeofninetests(arrayrows),wherethefirstcolumnwasassignedtothecuttingvelocity(V)andthesecondcolumntothefeedrate(f)andtheremainingwereassignedtotheinteractions.Theoutputsstudiedweresurfaceroughness(Ra)anddelaminationfactor(Fd),intheCFRPcompositematerial.