ASTM-D790-2010

Designation:D790–10StandardTestMethodsforFlexuralPropertiesofUnreinforcedandReinforcedPlasticsandElectricalInsulatingMaterials1ThisstandardisissuedunderthefixeddesignationD790;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheDepartmentofDefense.1.Scope*1.1Thesetestmethodscoverthedeterminationofflexuralpropertiesofunreinforcedandreinforcedplastics,includinghigh-moduluscompositesandelectricalinsulatingmaterialsintheformofrectangularbarsmoldeddirectlyorcutfromsheets,plates,ormoldedshapes.Thesetestmethodsaregenerallyapplicabletobothrigidandsemirigidmaterials.However,flexuralstrengthcannotbedeterminedforthosematerialsthatdonotbreakorthatdonotfailintheoutersurfaceofthetestspecimenwithinthe5.0%strainlimitofthesetestmethods.Thesetestmethodsutilizeathree-pointloadingsystemappliedtoasimplysupportedbeam.Afour-pointloadingsystemmethodcanbefoundinTestMethodD6272.1.1.1ProcedureA,designedprincipallyformaterialsthatbreakatcomparativelysmalldeflections.1.1.2ProcedureB,designedparticularlyforthosematerialsthatundergolargedeflectionsduringtesting.1.1.3ProcedureAshallbeusedformeasurementofflexuralproperties,particularlyflexuralmodulus,unlessthematerialspecificationstatesotherwise.ProcedureBmaybeusedformeasurementofflexuralstrengthonly.TangentmodulusdataobtainedbyProcedureAtendstoexhibitlowerstandarddeviationsthancomparabledataobtainedbymeansofProce-dureB.1.2Comparativetestsmayberuninaccordancewitheitherprocedure,providedthattheprocedureisfoundsatisfactoryforthematerialbeingtested.1.3ThevaluesstatedinSIunitsaretoberegardedasthestandard.Thevaluesprovidedinparenthesesareforinforma-tiononly.1.4Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.NOTE1—ThesetestmethodsarenottechnicallyequivalenttoISO178.2.ReferencedDocuments2.1ASTMStandards:2D618PracticeforConditioningPlasticsforTestingD638TestMethodforTensilePropertiesofPlasticsD883TerminologyRelatingtoPlasticsD4000ClassificationSystemforSpecifyingPlasticMateri-alsD4101SpecificationforPolypropyleneInjectionandExtru-sionMaterialsD5947TestMethodsforPhysicalDimensionsofSolidPlasticsSpecimensD6272TestMethodforFlexuralPropertiesofUnreinforcedandReinforcedPlasticsandElectricalInsulatingMaterialsbyFour-PointBendingE4PracticesforForceVerificationofTestingMachinesE691PracticeforConductinganInterlaboratoryStudytoDeterminethePrecisionofaTestMethod2.2ISOStandard:3ISO178Plastics—DeterminationofFlexuralProperties3.Terminology3.1Definitions—DefinitionsoftermsapplyingtothesetestmethodsappearinTerminologyD883andAnnexA1ofTestMethodD638.4.SummaryofTestMethod4.1Abarofrectangularcrosssectionrestsontwosupportsandisloadedbymeansofaloadingnosemidwaybetweenthesupports.Asupportspan-to-depthratioof16:1shallbeusedunlessthereisreasontosuspectthatalargerspan-to-depth1ThesetestmethodsareunderthejurisdictionofASTMCommitteeD20onPlasticsandarethedirectresponsibilityofSubcommitteeD20.10onMechanicalProperties.CurrenteditionapprovedApril1,2010.PublishedApril2010.Originallyapprovedin1970.Lastpreviouseditionapprovedin2007asD790–07´1.DOI:10.1520/D0790-10.2ForreferencedASTMstandards,visittheASTMwebsite,@astm.org.ForAnnualBookofASTMStandardsvolumeinformation,refertothestandard’sDocumentSummarypageontheASTMwebsite.3AvailablefromAmericanNationalStandardsInstitute(ANSI),25W.43rdSt.,4thFloor,NewYork,NY10036,*ASummaryofChangessectionappearsattheendofthisstandard.Copyright©ASTMInternational,100BarrHarborDrive,POBoxC700,WestConshohocken,PA19428-2959,UnitedStates.--`,`,`````,`,,```,,,,,,`,``-`-`,,`,,`,`,,`---ratiomayberequired,asmaybethecaseforcertainlaminatedmaterials(seeSection7andNote7forguidance).4.2Thespecimenisdeflecteduntilruptureoccursintheoutersurfaceofthetestspecimenoruntilamaximumstrain(see12.7)of5.0%isreached,whicheveroccursfirst.4.3ProcedureAemploysastrainrateof0.01mm/mm/min(0.01in./in./min)andisthepreferredprocedureforthistestmethod,whileProcedureBemploysastrainrateof0.10mm/mm/min(0.10in./in./min).5.SignificanceandUse5.1Flexuralpropertiesasdeterminedbythesetestmethodsareespeciallyusefulforqualitycontrolandspecificationpurposes.5.2Materialsthatdonotfailbythemaximumstrainallowedunderthesetestmethods(3-pointbend)maybemoresuitedtoa4-pointbendtest.Thebasicdifferencebetweenthetwotestmethodsisinthelocationofthemaximumbendingmomentandmaximumaxialfiberstresses.Themaximumaxialfiberstressesoccuronalineundertheloadingnosein3-pointbendingandovertheareabetweentheloadingnosesin4-pointbending.5.3Flexuralpropertiesmayvarywithspecimendepth,temperature,atmosphericconditions,andthedifferenceinrateofstrainingasspecifiedinProceduresAandB(seealsoNote7).5.4B