Standard Test Method for Measuring Damage Resistance of Fiber-Reinforced Polymer-Matrix Composite to Concentrated Quasi-Static Indentation Force

con ictbetweenterms,TerminologyD3878shallhaveprece-denceovertheotherstandards.

3.2De nitionsofTermsSpeci ctoThisStandard—Thetermsinthistestmethodmaycon ictwithgeneralusage.Thereisnotyetanestablishedconsensusconcerningtheuseoftheseterms.Thefollowingdescriptionsareintendedonlyforuseinthistestmethod.

NOTE1—Ifthetermrepresentsaphysicalquantity,itsanalyticaldimensionsarestatedimmediatelyfollowingtheterm(orlettersymbol)infundamentaldimensionform,usingthefollowingASTMstandardsym-bologyforfundamentaldimensionsshownwithinsquarebrackets:[M]formass,[L]forlength,[T]fortime,[u]forthermodynamictemperature,and[nd]eofthesesymbolsisrestrictedtoanalyticaldimensionswhenusedwithsquarebrackets,asthesymbolsmayhaveotherde nitionswhenusedwithoutthebrackets.

3.2.1contactforce,F[MLT 2],n—thetotalforceappliednormaltothefaceofthespecimenbytheindenter.

3.2.2damage,n—instructuresandstructuralmaterials,astructuralanomalyinamaterialorstructurecreatedbymanufacturingorserviceusage.

3.2.3damageresistance,n—instructuresandstructuralmaterials,ameasureoftherelationshipbetweentheforce,energy,orotherparameter(s)associatedwithaneventorsequenceofeventsandtheresultingdamagesizeandtype.3.2.4dentdepth,d[L],n—residualdepthofthedepressionformedbyanindenterafterremovalofload.Thedentdepthshallbede nedasthemaximumdistanceinadirectionnormaltothefaceofthespecimenfromthelowestpointinthedenttotheplaneoftheindentedsurfacethatisundisturbedbythedent.

3.2.5F1force,F1[MLT 2],n—contactforceatwhichtheforce/indenterdisplacementcurvehasadiscontinuityinforceorslope.

3.2.6indenterdisplacement,d[L],n—thedisplacementoftheindenterrelativetothespecimensupport.

3.2.7maximumforce,Fcontactforcealaminatewillmax[MLT 2],n—themaximumresist.ThisforceisobtainedfromtheF/dcurveafterapointisreachedwherethecontactforcedoesnotincreasewithincreasingindenterdisplacement.3.3Symbols:d=dentdepth(see3.2.4).F=contactforce(see3.2.1).F=FF1=1force(see3.2.5).

maximumforce(see3.2.7).

Nmax=

numberofplygroupsinalaminate’sstackingd

=sequence.

indenterdisplacement(see3.2.6).

4.SummaryofTestMethod

4.1Thequasi-staticindentation(QSI)testisusedtomea-surethedamageresistanceofauniform-thicknesslaminatedcompositespecimen.Anindentationforceisappliedslowlybypressingadisplacement-controlledhemisphericalindenterintothefaceofthespecimen.Thedisplacementisincreaseduntilthedesireddamagestateisreached.Proceduresarespeci edfordeterminingthedamageresistanceforasimplysupportedtestspecimenandforarigidlybackedtestspecimen.Thedamageresponseisafunctionofthetestcon guration.

4.2Arecordoftheappliedcontactforce/indenterdisplace-ment(F/d)isrecordedoneitheranX-Yrecorder,anequivalentreal-timeplottingdevice,orstoreddigitallyandpostprocessed.5.Signi canceandUse

5.1Susceptibilitytodamagefromconcentratedindentationforcesisoneofthemajorweaknessesofmanystructuresmadeofadvancedlaminatedcomposites.Knowledgeofthedamageresistanceofalaminatedcompositematerialsubjectedtoaconcentratedindentationforceisusefulforproductdevelop-mentandmaterialselection.

5.2TheQSItestmethodcanservethefollowingpurposes:5.2.1Toestablishquantitativelytheeffectsofstackingsequence, bersurfacetreatment,variationsin bervolumefraction,andprocessingandenvironmentalvariablesonthedamageresistanceofaparticularcompositelaminatetoaconcentratedquasi-staticindentationforce.

5.2.2Tocomparequantitativelytherelativevaluesofthedamageresistanceparametersforcompositematerialswithdifferentconstituents.Thedamageresponseparametersincluded,F1,andFmax,aswellastheF/dcurve.

5.2.3Toplaceacontrolledamountofdamageinaspecimenforsubsequentdamagetolerancetests.

5.2.4Toisolateandmeasuretheindentationresponseofthespecimenwithoutbending(rigidlybackedcon guration).6.Interferences

6.1TheQSItestsimulatestheforce/displacementrelation-shipsofmanyimpactsgovernedbyboundaryconditions(1-7).3Thesearetypicallyrelativelylarge-masslow-velocityhard-bodyimpactsonplateswitharelativelysmallunsup-portedregion.Thistestmethoddoesnotaddresswavepropa-gationandvibrationsinthespecimen,time-dependentmaterialbehavior,orinertia-dominatedimpactevents.

6.2Thedamageresponseofaspecimenisdependentonmanyfactors,includingtheindentergeometryandspecimensupportconditions.Consequently,comparisonscannotbemadebetweenmaterialsunlessidenticaltestcon gurations,identicaltestconditions,andidenticallaminatesareused.Therefore,alldeviationsfromthestandardtestcon gurationshouldbereportedintheresults.

6.3ForceF1doesnotrepresenttheinitiationofdamage,butgenerallyrepresentswhenthedisplacementoftheindenterisaffectedbylarge-scaledamageformation.Typically,matrixcracksandsmalldelaminationsformbeforethisforce.

6.4Thedentdepthmay“relax”orreducewithtimeoruponexposuretodifferentenvironmentalconditions.

6.5Treatmentandinterpretationofdelaminationgrowtharebeyondthescopeofthistestmethod.

6.6MaterialandSpecimenPreparation—Poormaterialfabricationpractices,lackofcontrolof beralignment,anddamageinducedbyimpropercouponmachiningareknowncausesofhighmaterialdatascatterincomposites.

6.7ApplicationtoOtherMaterials,Lay-Ups,andArchitec-tures:

3

Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendofthis

standard.