POLYMER‐TO‐CERAMIC TECHNOLOGY FOR FRICTION …
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Riverside Technology Park ‐ 2165 Technology Drive Schenectady, NY 12308‐1143 Copyright ® 2010‐2011 Starfire Systems, Inc. All rights reserved. Rev date: 03/12 Phone: 518.899.9336 Fax: 518.289.2261 www.starfiresystems.com POLYMER-TO-CERAMIC™ TECHNOLOGY POLYMER‐TO‐CERAMIC TM TECHNOLOGY FOR FRICTION APPLICATIONS Starfire Polymer‐to‐Ceramic Composite (PTCC) materials are carbon fiber reinforced ceramic composites which utilize Starfire Polymer‐to‐Ceramic TM technology and produce tough, high thermally stable composites. These PTCCs can be designed and used for frictional, structural, and thermal applications. Manufacture of Starfire PTCCs is simple and does not require expensive equipment, is easily machinable, and is environmentally friendly. The processing of PTCCs relies exclusively on pyrolysis of the thermoset resin to form a ceramic—no hazardous precursors are required, and no conversion reaction takes place which can compromise fibers, interface coatings, and negatively impact production yields. Why Ceramic Composites? Carbon fiber reinforced ceramic composites are especially important because when compared with metal, they offer such advantages as significant heat and corrosion resistance, high strengths at elevated temperatures, and reduced weight for a host of uses. However, one weakness of the material system is brittleness which is significantly improved by reinforcing the ceramic with tough, carbon fibers. Depending on the cost target and application, different reinforcements are available to address brittleness and encourage tough behavior. For high stress applications, continuous fiber reinforcement is available, and for lower stress and cost sensitive applications, short, chopped fiber reinforcement is available. Table 1 below describes some typical properties for composites produced with Starfire PTCCs. Because Starfire Systems develops and designs custom polymers, the possibilities are endless for a PTCC to perform to a customer requirement. In a friction application for automobiles and motorcycles, using a PTCC rotor, with a 70% reduction in mass compared to an iron rotor, can reduce total vehicle and rotating mass which improves gas mileage, and improves acceleration and vehicle handling. In aircraft friction, using PTCC rotors to replace carbon‐carbon is envisioned to yield reduced wear and increased brake life, reduced brake stack heights, and improved static coefficients, all at comparable cost of manufacture. Other ceramic composite technologies do exist in production. Each offers distinct advantages and disadvantages, and each has a place in the market. Table 2 below summarizes three (3) competing technologies and some details related to their relative cost to manufacture, temperature capability, and strengths. Starfire PTCC materials utilize LPI technology and are considered the most cost effective and safest means to create ceramic composites available. Table 1: Summary of Typical Data utilizing Starfire Polymer‐to‐Ceramic TM Technology Reinforcement Type – Starfire PTCC Cost Flexural Strength (ksi) Tensile Strength (ksi) Thermal Conductivity (W/m*°K) Z‐direction X‐Y‐direction Non‐Woven $$ 20‐24 15‐18 4 ‐‐‐ 2‐D Laminate $$$ 35‐42 35‐40 2 10 Chopped Fiber $ 15‐25 3‐6 4 8
Transcript of POLYMER‐TO‐CERAMIC TECHNOLOGY FOR FRICTION …
RiversideTechnologyPark‐2165TechnologyDrive Schenectady,NY12308‐1143 Copyright®2010‐2011StarfireSystems,Inc.Allrightsreserved.Revdate:03/12
Phone:518.899.9336Fax:518.289.2261
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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
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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
