Designation:C747−16AnAmericanNationalStandardStandardTestMethodforModuliofElasticityandFundamentalFrequenciesofCarbonandGraphiteMaterialsbySonicResonance1ThisstandardisissuedunderthefixeddesignationC747;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope*1.1Thistestmethodcoversdeterminationofthedynamicelasticpropertiesofisotropicandnearisotropiccarbonandgraphitematerialsatambienttemperatures.Specimensofthesematerialspossessspecificmechanicalresonantfrequenciesthataredeterminedbytheelasticmodulus,mass,andgeometryofthetestspecimen.Thedynamicelasticpropertiesofamaterialcanthereforebecomputedifthegeometry,mass,andmechani-calresonantfrequenciesofasuitable(rectangularorcylindri-cal)testspecimenofthatmaterialcanbemeasured.DynamicYoung’smodulusisdeterminedusingtheresonantfrequencyintheflexuralorlongitudinalmodeofvibration.Thedynamicshearmodulus,ormodulusofrigidity,isfoundusingtorsionalresonantvibrations.DynamicYoung’smodulusanddynamicshearmodulusareusedtocomputePoisson’sratio.1.2Thistestmethoddetermineselasticpropertiesbymea-suringthefundamentalresonantfrequencyoftestspecimensofsuitablegeometrybyexcitingthemmechanicallybyasingularelasticstrikewithanimpulsetool.Specimensupports,impulselocations,andsignalpick-uppointsareselectedtoinduceandmeasurespecificmodesofthetransientvibrations.Atrans-ducer(forexample,contactaccelerometerornon-contactingmicrophone)sensestheresultingmechanicalvibrationsofthespecimenandtransformsthemintoelectricsignals.(SeeFig.1.)Thetransientsignalsareanalyzed,andthefundamentalresonantfrequencyisisolatedandmeasuredbythesignalanalyzer,whichprovidesanumericalreadingthatis(orisproportionalto)eitherthefrequencyortheperiodofthespecimenvibration.Theappropriatefundamentalresonantfrequencies,dimensions,andmassofthespecimenareusedtocalculatedynamicY...
