ASTM_F_2977_-_13.pdf

Designation:F297713Standard Test Method forSmall Punch Testing of Polymeric Biomaterials Used inSurgical Implants1This standard is issued under the fixed designation F2977;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of mechanicalbehavior of polymeric biomaterials by small punch testing ofminiature disk specimens(0.5 mm in thickness and 6.4 mm indiameter).The test method has been established for character-izing surgical materials after ram extrusion or compressionmolding(1-3)2;for evaluating as-manufactured implants andsterilization method effects(4,5);as well as for testing ofimplants that have been retrieved(explanted)from the humanbody(6,7).1.2 The results of the small punch test,namely the peakload,ultimate displacement,ultimate load,and work to failure,provide metrics of the yielding,ultimate strength,ductility,andtoughness under multiaxial loading conditions.Because themechanical behavior can be different when loaded underuniaxial and multiaxial loading conditions(8),the small punchtest provides a complementary mechanical testing technique tothe uniaxial tensile test.However,it should be noted that thesmall punch test results may not correlate with uniaxial tensiletest results.1.3 In addition to its use as a research tool in implantretrieval analysis,the small punch test can be used as alaboratory screening test to evaluate new materials withminimal material waste(1).1.4 The small punch test has been applied to other polymers,including polymethyl methacrylate(PMMA)bone cement,polyacetal,and high density polyethylene(HDPE),ultra highmolecular weight polyethylene(UHMWPE),and polyethere-therketone(PEEK)(2,3,5,9,10).This standard outlinesgeneral guidelines for the small punch testing of implantablepolymers.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:3D695 Test Method for Compressive Properties of RigidPlasticsD883 Terminology Relating to PlasticsE4 Practices for Force Verification of Testing MachinesE83 Practice for Verification and Classification of Exten-someter SystemsF1714 Guide for Gravimetric WearAssessment of ProstheticHip Designs in Simulator DevicesF1715 Guide for Wear Assessment of Prosthetic Knee De-signs in Simulator Devices(Withdrawn 2006)4F2003 Practice for Accelerated Aging of Ultra-High Mo-lecular Weight Polyethylene after Gamma Irradiation inAirF2102 Guide for Evaluating the Extent of Oxidation inPolyethylene Fabricated Forms Intended for SurgicalImplants3.Terminology3.1 Definitions:3.1.1 small punch test,na test wherein the specimen is ofminiature size relative to conventional mechanical testspecimens,is disk-shaped,and is loaded axisymmetrically inbending by a hemispherical-head punch.NOTE1The features of a typical small punch test load versusdisplacement curve for PEEK,UHMWPE,and PMMA bone cement areillustrated in Fig.1(a-c)and Fig.2.3.2 Definitions of Terms Specific to This Standard:3.2.1 peak load,nan initial local maximum in the loadversus displacement curve(Fig.2).In certain polymer formu-lations such as radiation crosslinked UHMWPE materials,theload versus displacement curve increases monotonically and a1This test method is under the jurisdiction ofASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved June 1,2013.Published August 2013.DOI:10.1520/F2977-13.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.4The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 shoulder,rather than an initial peak load,may be observed.Forbrittle materials,the load versus displacement behavior may becompletely linear,in which case no peak load would beobserved.3.2.2 ultimate load,nthe load at rupture(failure)of thespecimen that is calculated at the first point before the breakingpoint in the curve where the root of the first derivative is equalto zero(Fig.2).3.2.3 ultimate displacement,nthe displacement at rupture(failure)of the specimen(Fig.2).3.2.4 work to failure,nthe area under the load versusdisplacement