复合材料自行车架.ppt

Fiberdirectionandstackingsequencedesignforbicycleframemadeofcarbon epoxycompositelaminateThomasJin CheeLiua bHuang ChiehWubaDepartmentofMechanicalEngineering MingChiUniversityofTechnology Taishan TaipeiCounty243 TaiwanbGraduateInstituteofElectro MechanicalEngineering MingChiUniversityofTechnology Taishan TaipeiCounty243 Taiwan Accordingtothemaximumstresstheoryandtheresultsofstrength to stressratios thefiberdirectionandstackingsequencedesignforthebicycleframemadeofthecarbon epoxycompositelaminateshavebeendiscussedinthispaper Threetestingmethodsforthebicycleframe I etorsional frontal andverticalloadings areadoptedintheanalysis Fromthefiniteelementresults thestackingsequences 0 90 90 0 sand 0 90 45 45 sarethegooddesignsforthecompositebicycleframes Onthecontrary theuni directionallaminates i e 0 0 0 0 s 90 90 90 90 s 45 45 45 45 sand 45 45 45 45 s arethebaddesigns Inaddition weakregionsoffailureoccuratthefilletsandconnectionsoftheframe i e thestressconcentrationregions Allweakpointsoccurattheinnerorouterlayerofthelaminatedcompositetube The0 plyand90 plylocatedontheinnerandouterlayerofthetubecaneffectivelyresistthehigherstressatitslocation ABSTRACT 1IntroductionCompositematerialswhicharecomposedofreinforcedfibersandplasticsmatrixhavehighstrength to weightandstiffness to weightratios Theyhaveuniqueadvantagesovermonolithicmaterials suchashighstrength highstiffness longfatiguelifelowdensity lowdensitycorrosionresistance wear resistance andenvironmentalstability 1 Duotoabovecharacteristics thelaminatelaminated fiber reinforcedcompositematerialssuchascarbor epoxyglass polyesterarewidelyappliedinaircraft military automotive marine andandstructures 1 2 Thebicyclesarepopularsportsequipmentsortraffictools Theframeofthebicycleisthemainstructuretosupporttheexternalloads Traditionalmaterialsofthebicycleframearethesteeloraluminumalloy Forthepurposeofreducingweight thecarbon epoxycompositematerialsarenowwidelyusedtomakethebicycleframes Anexampleofthecarbon epoxybicycleframe 1 onlyweights1 36kg whichismuchlessthanthe5kgweightofthecorrespondingsteelframe Inthedesignprocessofthebicycle thestructuralanalysisoftheframeorotherpartsisaveryimportantstage Withtheaidoftheoreticalornumericalcalculations thestrengthandstiffnessofthebicyclestructurescanbepredictedandmodifiedtotheoptimaldesignbeforethemanufactureoftheprototypeandcommercialproducts Thefiniteelementmethodisoneofthenumericalcalculationsappliedinvariousphysicalproblems Itusuallyplaysamajorroletocalculatethestressanddeformationofthestructures In1986 thefiniteelementmethodwasappliedinthedesignofthesteelandaluminumbicycleframes 3 TheEulerbeamelements orframeelements wereadoptedinthesimplifiedmodelofthewholebicycleframe Thedeflection vonMisesstressandstrainenergyoftheframeundervariousloadingconditionswereobtained Thedesignstrength ridingperformanceandweightreductionofthebicyclehavebeenconsideredanddiscussed 3 Thefiniteelementmethodwasalsoadoptedtoanalyzethestructuralbehaviorsofthecompositebicycleframes 4 5 Theshellelementswereusedtomodelthecompositebicycleframe 4 Inthatstudy twotypesofshapesofthegraphite epoxycompositeframewereanalyzedunderthreeloadingconditions The0 fiberdirectioncorrespondsroughlytoalinewhichfollowstheshapeofthebicyclefromthefronttubetothereardropouts Thestackingsequences 02 90 sand 02 902 0 swereused respectively inthelowandhighloadedregionsoftheframe 4 Thesingle layerequivalentmodelwasadoptedtosimulatethemulti plycompositelaminateofthebicycleframe 5 Theeffectivematerialconstantsofthe8 plycarbon epoxylaminatewereobtainedbythemathematicaltransformation Underthetorsionalloading theresultsshowedthatthestacking 0 45 45 0 scancausethehigheststiffness 5 Inaddition higherstresseshappenedontheconnectedregionsandfilletsoftheframetubes Inthispaper thefiberdirectionandstackingsequencedesignforthebicycleframemadeofthecarbon epoxycompositelaminateswillbediscussed Undertorsional frontal andverticalloadings thenormalandshearstresseswithrespecttotheprincipalmaterialcoordinatesystemofeachplywillbeobtainedfromthefiniteelementanalyses Themaximumstresstheory 1 9 isusedtobethefailurecriterion Thestrength to stressratioRisdefinedasthedesignparameterfortheoptimalselectionfrom33stackingsequencesoflaminates ThelargervalueofRimpliesthehighersafetyfactoroftheframestructure ThefiniteelementsoftwareANSYS 11 willbeusedtoanalyzethestressfieldandstructuralbehaviors Flg1 CADmoldofbicycleframe Flg2 maindimensionsofbicycleframe 2 Problemdefinitions2 1 Bicycleframeandcompositelaminates Table1Maindimensionsofbicycleframe Table2Stackingsequencesoflaminatesinthisstudy Table3Additionalstackingsequencesoflaminatesinthisstudy 2 2 ThreetestingmethodsTheboundaryandloadingconditionsforthefiniteelementanalysesarebasedonthetestingmethodsofthebicycleframe AccordingtopastRefs 5 13 threetestingmethods i e torsional frontalandverticalloadings areconsideredinthispaper Tofindthebetterstackingdesignofeachtest thesethreetestsareanalyzedanddiscussedseparably Fig 4 Torsionalloadingtest Fig 5 Frontalloadingtest Inthisstudy thestaticfrontalloadFf 490Nisappliedoneachsideofthefronttube Theframeisfixedatbothreardropouts thestaticverticalloadsareFv1 6kgf 58 8N Fv2 67kgf 656 6N andFv3 13 5kgf 132 3N Thetotalverticalloadis100kgf Theframeisfixedatreardropoutsandfronttubeends Fig6Verticalloadingtest 3 Methodsofanalyses3 1 OrthotropicmaterialpropertyUndertheCartesiancoordinate1 2 3 theconstitutiveequationoftheorthotropicmaterialsuchasthecarbon epoxycompositeis 1 Table4Materialconstantsofcarbon epoxycomposite 5 thesubscript1isthefiberaxis 3 2 Finiteelementmodels Fig 7 Finiteelementmodelfortorsionalloadingtest Fig 8 Finiteelementmodelforfrontalorverticalloadingtest Fig 9 Directionsofx axesofRCSforeachtube Fig 10 Directionsofx axesofRCSonlocalfillets 3 3 FailurecriterionThemaximumstresstheory 1 9 isusedtobethefailurecriterioninthisstudy Themaximumstresstheoryisexpressedasfollows 1 Strengthvaluesofcarbon epoxycomposite 14 Inthispaper thestrength to stressratioRisdefinedasfollows 3 4 Designparameter 4 Resultsanddiscussion 4 1 Resultsoftorsionalloadingtest Table6StressesofCase1with 0 90 45 45 sundertorsionalloading Table8ValuesofRitm Ricm RijmandRminfordifferentcasesundertorsionalloading Table7ValuesofRitm Ricm RijmandRminfordifferentcasesundertorsionalloading 4 2 Resultsoffrontalloadingtest Table9ValuesofRitm Ricm Rijm andRminfordifferentcasesunderfrontalloading Table10ValuesofRitm Ricm Rijm andRminfordifferentcasesunderfrontalloading 4 3 Resultsofvertical