ASTM_D_790_-_10.pdf

Designation:D79010Standard Test Methods forFlexural Properties of Unreinforced and Reinforced Plasticsand Electrical Insulating Materials1This standard is issued under the fixed designation D790;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.This standard has been approved for use by agencies of the Department of Defense.1.Scope*1.1 These test methods cover the determination of flexuralproperties of unreinforced and reinforced plastics,includinghigh-modulus composites and electrical insulating materials inthe form of rectangular bars molded directly or cut from sheets,plates,or molded shapes.These test methods are generallyapplicable to both rigid and semirigid materials.However,flexural strength cannot be determined for those materials thatdo not break or that do not fail in the outer surface of the testspecimen within the 5.0%strain limit of these test methods.These test methods utilize a three-point loading system appliedto a simply supported beam.A four-point loading systemmethod can be found in Test Method D6272.1.1.1 Procedure A,designed principally for materials thatbreak at comparatively small deflections.1.1.2 Procedure B,designed particularly for those materialsthat undergo large deflections during testing.1.1.3 ProcedureAshall be used for measurement of flexuralproperties,particularly flexural modulus,unless the materialspecification states otherwise.Procedure B may be used formeasurement of flexural strength only.Tangent modulus dataobtained by Procedure A tends to exhibit lower standarddeviations than comparable data obtained by means of Proce-dure B.1.2 Comparative tests may be run in accordance with eitherprocedure,provided that the procedure is found satisfactory forthe material being tested.1.3 The values stated in SI units are to be regarded as thestandard.The values provided in parentheses are for informa-tion only.1.4 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.NOTE1These test methods are not technically equivalent to ISO 178.2.Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD638 Test Method for Tensile Properties of PlasticsD883 Terminology Relating to PlasticsD4000 Classification System for Specifying Plastic Materi-alsD4101 Specification for Polypropylene Injection and Extru-sion MaterialsD5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensD6272 Test Method for Flexural Properties of Unreinforcedand Reinforced Plastics and Electrical Insulating Materi-als by Four-Point BendingE4 Practices for Force Verification of Testing MachinesE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:3ISO 178 PlasticsDetermination of Flexural Properties3.Terminology3.1 DefinitionsDefinitions of terms applying to these testmethods appear in Terminology D883 and Annex A1 of TestMethod D638.4.Summary of Test Method4.1 A bar of rectangular cross section rests on two supportsand is loaded by means of a loading nose midway between thesupports.A support span-to-depth ratio of 16:1 shall be usedunless there is reason to suspect that a larger span-to-depth1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.10 on MechanicalProperties.Current edition approved April 1,2010.Published April 2010.Originallyapproved in 1970.Last previous edition approved in 2007 as D790 071.DOI:10.1520/D0790-10.2For 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.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 ratio may be required,as may be the case for certain laminatedmaterials(see Section 7 and Note 7 for guidance).4.2 The specimen is deflected until rupture occurs in theouter surface of the test specimen or until a maximum strain(see 12.7)of 5.0%is reached,whichever occurs first.4.3 Procedure A employs a strain rate of 0.01 mm/mm/min(0.01 in./in./min)and is the preferred procedure for this testmethod,while Procedure B employs a strain rate of 0.10mm/mm/min(0.10 in./in./min).5.Significance and Use5.1 Flexural properties as determined by these