polymer‐to‐ceramic technology for friction …

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POLYMER-TO-CERAMIC™ TECHNOLOGY

POLYMER‐TO‐CERAMICTMTECHNOLOGYFORFRICTIONAPPLICATIONSStarfirePolymer‐to‐CeramicComposite(PTCC)materialsarecarbonfiberreinforcedceramiccompositeswhichutilizeStarfirePolymer‐to‐CeramicTMtechnologyandproducetough,highthermallystablecomposites.ThesePTCCscanbedesignedandusedforfrictional,structural,andthermalapplications.ManufactureofStarfirePTCCsissimpleanddoesnotrequireexpensiveequipment,iseasilymachinable,andisenvironmentallyfriendly.TheprocessingofPTCCsreliesexclusivelyonpyrolysisofthethermosetresintoformaceramic—nohazardousprecursorsarerequired,andnoconversionreactiontakesplacewhichcancompromisefibers,interfacecoatings,andnegativelyimpactproductionyields.

WhyCeramicComposites?Carbonfiberreinforcedceramiccompositesareespeciallyimportantbecausewhencomparedwithmetal,theyoffersuchadvantagesassignificantheatandcorrosionresistance,highstrengthsatelevatedtemperatures,andreducedweightforahostofuses.However,oneweaknessofthematerialsystemisbrittlenesswhichissignificantlyimprovedbyreinforcingtheceramicwithtough,carbonfibers.Dependingonthecosttargetandapplication,differentreinforcementsareavailabletoaddressbrittlenessandencouragetoughbehavior.Forhighstressapplications,continuousfiberreinforcementisavailable,andforlowerstressandcostsensitiveapplications,short,choppedfiberreinforcementisavailable.Table1belowdescribessometypicalpropertiesforcompositesproducedwithStarfirePTCCs.BecauseStarfireSystemsdevelopsanddesignscustompolymers,thepossibilitiesareendlessforaPTCCtoperformtoacustomerrequirement.

Inafrictionapplicationforautomobilesandmotorcycles,usingaPTCCrotor,witha70%reductioninmasscomparedtoanironrotor,canreducetotalvehicleandrotatingmasswhichimprovesgasmileage,andimprovesaccelerationandvehiclehandling.Inaircraftfriction,usingPTCCrotorstoreplacecarbon‐carbonisenvisionedtoyieldreducedwearandincreasedbrakelife,reducedbrakestackheights,andimprovedstaticcoefficients,allatcomparablecostofmanufacture.

Otherceramiccompositetechnologiesdoexistinproduction.Eachoffersdistinctadvantagesanddisadvantages,andeachhasaplaceinthemarket.Table2belowsummarizesthree(3)competingtechnologiesandsomedetailsrelatedtotheirrelativecosttomanufacture,temperaturecapability,andstrengths.StarfirePTCCmaterialsutilizeLPItechnologyandareconsideredthemostcosteffectiveandsafestmeanstocreateceramiccompositesavailable.

Table1:SummaryofTypicalDatautilizingStarfirePolymer‐to‐CeramicTMTechnology

ReinforcementType–StarfirePTCC Cost Flexural

Strength(ksi)TensileStrength

(ksi)ThermalConductivity(W/m*°K)Z‐direction X‐Y‐direction

Non‐Woven $$ 20‐24 15‐18 4 ‐‐‐2‐DLaminate $$$ 35‐42 35‐40 2 10ChoppedFiber $ 15‐25 3‐6 4 8

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ApplicationsinFrictionMotorcycle,automobileandaircraftbrakesmadefromStarfirePTCCmaterialsareonelogicalselectionofthematerialsystemduetoitshighthermalcapability,highstrengthandtoughness,andlowweightcomparedtometalalternatives.

Inlimitedproductionvolume,StarfirePTCCmaterialswereutilizedasmotorcyclebrakerotorsunderthetradename,STARBlade®asshowninFigure1.Thesesingle‐blade,non‐ventilatedC/SiCrotorswerewellreceivedbythestreetdriverandtrackraceralikeastheyofferedamazingbrakingcapacitywithnofade.Structurally,itwasshowntheseSTARBlade®rotorswerestrong,tough,anddurableenoughtolast>100,000mileswithvirtuallynorotorwear.Duetotheirreducedweightcomparedtometalbrakerotors,handlingwassignificantlyimprovedfor

thebikerider.Inadditiontothemotorcyclebrakerotor,StarfirehasdemonstratedthatPTCCmaterialshavemorethanadequatestrength,toughness,anddurabilitytoprovideabrakingsolutionforhighperformanceautomobiles.Figure2demonstratesthataSTARBlade®PTCCautomotiverotorcanbemoldednearlynetinshape,includingattachmentlugs,crossdrillholesandventilation,andiscomprisedofaStarfirebasedchoppedfiberreinforcedmoldingcompound.StarfirehasalsodemonstratedinFigure3thesecompositerotorscanbemadeinvolume.

Ifmoldednetshape,themoldedpartrequiresonlyminimalfinishgrindingoftherotorsurfaces,significantlyreducingrawmaterialandmachiningcosts.TheexpectedproductioncostofthisStarfirePTCCrotorislowerthanEuropeancarbon‐ceramicbrakesnowofferedonlyonhighendperformancecars,likePorscheandFerrari.

FrictionalperformanceandwearofStarfirePTCCautorotorsisoutstanding.Withanaveragecoefficientoffrictionofabout0.46,stablefrictionandlowweararealreadypossibleusingcommerciallyavailablesemi‐metallicpads,andwearisexpectedtoimprovewithspeciallyformulatedpadliningmaterials.Forthistest,highspeed,lowvehiclemasssuper‐carconditionswereselectedtoillustrateperformancecapability.Figure4showsafadeandhotperformancesectionofadynotest,andillustratesthestabilityofthefrictioncoefficientwithincreasingtemperature,butalsoshowssomepressuresensitivity.Inadditiontooutstandingperformance,othertestinghasshownthisSTARBlade®PTCCformulationtowithstand

MaterialType

ReinforcementType Cost Technical

Maturity

TemperatureCapability

(°C)

ThermalConductivity–Z‐direction

Toughness Strength

LPI–LiquidPolymerInfiltrationTechnology(PTCC)

•ContinuousFiber/Fabric•ChoppedFiber•Non‐Woven

$ Moderate >1,400°C Low High High

LSI–LiquidSiliconizationTechnology

•ChoppedFiber•Non‐Woven $$ High 1,400°CMax Medium/

High Low Moderate

CVI–ChemicalVaporInfiltrationTechnology

•Continuous•Fiber/Fabric•Non‐Woven

$$$$ Moderate >1,600°C Medium High High

Figure1:STARBlade®PTCCMotorcycleRotor

Figure3:394mmand380mmPTCCSTARBlade®rotorsin‐processforqualificationtesting

Figure2:SingleoperationmoldedautoPTCCSTARBlade®rotorwithfeatures

Figure4:ISO26867PerformanceTest;3609024;Fade,HotPerformance

Table2:Assessmentofvariousleadingfiberreinforced,ceramiccompositetechnology

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torquesgreaterthan4,800N*m—4xgreaterthanthemaximumdesignallowableforthiscomponent.ExceptionalperformancewasachieveddespiteutilizingcommerciallyavailablepadliningswhichwerenotspecificallydesignedfortheStarfirePTCCceramicrotortechnology.PerformancecanonlybeimprovedonceapadliningmaterialisspecificallydesignedtomatchtheuniquepropertiesoftheStarfirePTCCrotormaterialsystem.

PerformanceofPTCCRotorsComparedtoIronRotorsWhilePTCCrotorsare1/3thedensityofironrotors,theyarealsolowerinthermalmassandthermalheatcapacity(Cp),thecapacitytostoreheatwhichcomesaboutfromtheconversionofkineticenergytothermalenergyduringbraking.Thecurrentstateoftheartpadliningslimittheoverallcapabilityoftheceramicbrakesystemandstarttoexhibitfadecharacteristicswhenthepadliningsreachtheiruppertemperatureandpressurelimitations.Thispadfadebehaviorisevidentforbothironrotors,aswellasceramicrotorsofanyformulation.Starfirehasevaluated,atnearlyidenticaltestconditions,aStarfirePTCCrotor(A)andastandardironrotor(B)usingpadsdesignedforagenericceramicrotor,andaniron

rotorrespectivelyasshowninFigure5.Thetestsimulatedalarge,fullsizedSUVvehicleoperatingathighspeeds,startedthetestatrotortemperaturesof150°Cand500°C,andincreasedthebrakecaliperpressuretonearitsdesignmaximum.Inbothcases,thesystemsdemonstrateacceptableperformance,withsomevariation,butshowednoticeablepadfade.Thisperformancefadeisapaddominatedcharacteristicanditisclearperformancedegradesasthepadsarepushedbeyondtheirdesignlimitandultimatelyreducestheperformancepotentialofthesystem.

TheStarfirePTCCrotorformulationismorethancapableofhandlingtheenergyrequiredtofunctionasabrake,however,eventhecurrenthigh‐performancesemi‐metallicliningsstruggletokeepup.Starfirehasthecapabilitytoformulatespecializedpolymersaspadadditivesandcan,withtheassistanceofapadliningformulator,co‐developapaddesignedfortheuniquecharacteristicsofthePTCCrotortechnology.WithapadliningspecificallyformulatedandmodifiedforStarfirePTCCs,itispossibletohaveaceramicbrakingsolutionwhichoffersequivalentperformancetothatofanironrotor,butwiththereducedweightandimprovedwearconsistentwithaceramiccomposite.

AlternateFrictionMaterialsforRotorsandPadLiningsWhenselectingarotorandpadliningpair,itisclearthereisnoone‘best’materialforallapplicationsandconditions.Whatmustbeconsideredarefactorssuchas:maturityofthetechnology,cost,size,performance,andthermalmanagement.Whilesomeformulationsshowexceptionalpropertiesinonearea,theymaystumbleinothers.Asceramiccompositetechnologyisfurthermatured,itsreliabilitywillcontinuetoimprove,ceramicmanufacturingtechniqueswillbemoreaccepted,andcostwillcontinuetogodown.Thesebenefitswillcontinuetomakeceramictechnologymoreattractiveforlargevolumemanufacturing.SomerelativecharacteristicsofeachfrictiontechnologyareshowninTable3below.

Material Densityg/cc ThermalConductivity CTE Cost

Iron 7‐8 High High $StarfirePTCCC/SiCorC/SiOC 2.2‐2.3 Low Low $$$Carbon‐CeramicLSI 2.2‐2.4 Medium Low $$IronCladAluminum 6.0 Medium Medium $$AluminumMMC 2.5‐3.5 High High $$Titanium 4.5 Low Medium $$$

Figure5:ISO26867PerformanceTest;PTCCSTARBlade®Rotor,andIronRotor;HotPerformanceandPressureLine

Table3:ComparativeTypicalPropertiesofVariousCommonFrictionMaterials

RiversideTechnologyPark‐2165TechnologyDrive Schenectady,NY12308‐1143 Copyright®2010‐2011StarfireSystems,Inc.Allrightsreserved.Revdate:03/12

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AircraftBrakeFrictionStarfireparticipatedintheCeramicCompositeAircraftBrake(CCAB)programwhichwasfundedbytheAirForceResearchLab(AFRL)andtheOhioAerospaceInstitute(OAI)todevelopaceramicbrakingsystemforcommercialaircraftwithgreatsuccess.StarfirewonthePhaseIsub‐scaleportionwithoutstandingpropertiesandthelowestwearofallparticipants.Propertiesgeneratedfromthisprogramaresummarizedinthetable4below.

PhaseIIfullsizedtestingyieldedopportunitiestooptimizethedesignasStarfireC/SiCmaterialexperiencedhighwear.Althoughlittletestingofthefullsizedpartstookplace,StarfirefeelsthePTCCmaterialsystemcanbecommercializedasafunctionalaircraftbrakesystemandcanyieldthepromiseofalowwearingceramicbrake,onewithsimilarmasstocarbon‐carbonbutwithbetteroverallperformance.

HeavyVehicle,IndustrialBrakeStarfirehastestedPTCCrotortechnologyonheavy,industrialvehicleapplicationswithmixedresults.Initialtestswereconductedusingoriginalequipment(OE)liningsdesignedspecificallyformetallicrotors,insteadofliningsspecificallydesignedforceramicrotors,whichwouldalsoincludegreatersweptpadcontactarea.Figure6illustratesoneofthetwo(2)testedsystems,bothyieldedlowwear,loweffectivenessvalues.Astested,thesystemswerepressurelimitedduetothecapabilityoftheexistingbrakingcalipersusedinthefieldtoday.Encouragingly,therotorswerecapableofhandlingsufficienttorque(>1,350N*m),generatedfrictionandyieldedlowwear,butfellshortofasuccessduetoanon‐optimizedpadlining.Toimproveperformanceonthisandsimilartests,Starfirehasthecapabilitytodevelopspecializedpolymerpadadditives.Withtheseadditives,andwiththeassistanceofapadliningformulator,Starfirecanco‐developapaddesignedfortheuniquecharacteristicsofthePTCCrotortechnology.Additionally,thistestingindicatesadrop‐in‐replacementceramicrotorispossibleandcanpotentiallyofferareduced‐massceramicbrakerotoroptiontoexistingvehiclesinthefield,providedanimprovedliningcanbeoffered.

VersatileHybridRotorDesign–PTCC+MMC=HighPerformanceUtilizingStarfireSystems’proprietaryPTCCfrictionmaterialandametalmatrixcomposite(MMC)core,TurbineRotorshasdevelopedapatentedhybridautorotorconceptwhichoffersthebenefitofreducedweightcomparedtoironandsteel,thehighperformanceofanexoticceramiccompositefrictionmaterial,allatalowprice.Atbrakingtemperatureswherenormalmetallicfrictionsolutionssoften,oxidize,warpanddistort,orexhibitfade,theTurbineRotorshybridconceptshines.Thisdesign,showninfigure7,combinesprovenmetalmatrixcompositecastingtechnologytocreateastructuralcore,withtheestablishedtechnologyofaStarfirePTCCfrictionalsurfacetoofferafrictionalsystemcapableofgettingnoticed.WithmultiplePTCCfrictionsurfacestochosefrom,rangingfromaggressivetolowimpact,theTurbineRotorsconceptisgame‐changingtechnologyfortheracingcommunity.

Property UnitofMeasure Value

CarbonPreformType ‐‐‐ Non‐WovenDensity g/cc 2.0‐2.3FlexuralStrength,20°C ksi 24‐25CompressiveStrength ksi 63InterlaminarShear ksi 12‐13ThermalConductivity,800C‐1000°C W/m*°K 5.0‐5.5

Toughness mPa*m(1/2) 7

Table4:ThermalandMechanicalDataofStarfireC/SiCPTCCmanufacturedfortheCCABAirCraftBrakeDevelopmentProgram

Figure6:STARBlade®PTCCRotorPostTest

Figure7:TurbineRotors'HybridRotor