ASTM_C_651_-_15.pdf

Designation:C65115An American National StandardStandard Test Method forFlexural Strength of Manufactured Carbon and GraphiteArticles Using Four-Point Loading at Room Temperature1This standard is issued under the fixed designation C651;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 U.S.Department of Defense.1.Scope*1.1 This test method covers determination of the flexuralstrength of manufactured carbon and graphite articles using asimple beam in four-point loading at room temperature.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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:2C78 Test Method for Flexural Strength of Concrete(UsingSimple Beam with Third-Point Loading)C1161 Test Method for Flexural Strength of AdvancedCeramics at Ambient TemperatureE4 Practices for Force Verification of Testing MachinesE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Definitions:3.1.1 flexural strength,nproperty of a solid material thatindicates its ability to withstand a flexural or transverse load,obtained through a measurement of the ultimate load-carryingcapacity of a specified beam in bending.4.Significance and Use4.1 This test method may be used for material development,quality control,characterization,and design data generationpurposes.4.2 This test method determines the maximum loading on agraphite specimen with simple beam geometry in 4-pointbending,and it provides a means for the calculation of flexuralstrength at ambient temperature and environmental conditions.5.Apparatus5.1 The testing machine shall conform to the requirementsof Practices E4.5.2 The four-point loading fixture shall consist of bearingblocks or cylindrical bearings spaced in a third-point loadingconfiguration(see Test Method C78).5.3 The fixture shall ensure that forces applied to the beamare normal only and without eccentricity through the use ofspherical bearing blocks(see Test Method C78)or articulatingroller bearing assemblies(see Test Method C1161).5.3.1 The bearing block or roller bearing diameter shall bebetween110and120of the specimen support span.A hardenedsteel bearing block or its equivalent is necessary to preventdistortion of the loading member.Support surfaces must befree to pivot or rotate to relieve frictional constraints.5.4 The directions of loads and reactions may be maintainedparallel by judicious use of linkages,rocker bearings,andflexure plates.Eccentricity of loading can be avoided by theuse of spherical bearing blocks or articulating roller bearings.Provision must be made in fixture design for the relief oftorsional loading to less than 5%of the nominal specimenstrength.Refer to the attached figure for a suggested four-pointloading fixture.6.Test Specimen6.1 PreparationThe test specimen shall be prepared toyield a parallelepiped of rectangular cross section.The facesshall be parallel and flat within 0.025 mm mm of length.Inaddition,the samples having a maximum particle size less than0.150 mm in diameter must be finished so that the surface1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.F0 on Manufactured Carbon and Graphite Products.Current edition approved Oct.1,2015.Published November 2015.Originallyapproved in 1970.Last previous edition approved in 2013 as C651 13.DOI:10.1520/C0651-15.2For 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.*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 roughness is less than 3 m Ra.Sample edges should be freefrom visible flaws and chips.NOTE1For ease of machining to conventional standards,3 m Ra isequivalent to 125 in.AA.For finishing of specimens with maximumparticle sizes of greater than 0.150 mm,grain structure and porosity canlimit the accurate measurement of roughness.In these cases,the surfaceroughness should be visually equivalent to 3 m Ra as estimated based onthe visible surface of th