ASTM_C_1557_-_14.pdf

Designation:C155714Standard Test Method forTensile Strength and Youngs Modulus of Fibers1This standard is issued under the fixed designation C1557;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 preparation,mounting,andtesting of single fibers(obtained either from a fiber bundle ora spool)for the determination of tensile strength and Youngsmodulus at ambient temperature.Advanced ceramic,glass,carbon and other fibers are covered by this test standard.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 may involve hazardous materials,operations,and equipment.This standard does not purport toaddress all of the safety concerns,if any,associated with itsuse.It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2C1239 Practice for Reporting Uniaxial Strength Data andEstimating Weibull Distribution Parameters for AdvancedCeramicsD3878 Terminology for Composite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE1382 Test Methods for Determining Average Grain SizeUsing Semiautomatic and Automatic Image Analysis3.Terminology3.1 Definitions:3.1.1 bundlea collection of parallel fibers.Synonym,tow.3.1.2 mounting taba thin paper,cardboard,compliantmetal,or plastic strip with a center hole or longitudinal slot offixed gage length.The mounting tab should be appropriatelydesigned to be self-aligning if possible,and as thin as practi-cable to minimize fiber misalignment.3.1.3 system compliancethe contribution by the load trainsystem and specimen-gripping system to the indicated cross-head displacement,by unit of force exerted in the load train.3.2 For definitions of other terms used in this test method,refer to Terminologies D3878 and E6.4.Summary of Test Method4.1 A fiber is extracted randomly from a bundle or from aspool.4.2 The fiber is mounted in the testing machine,and thenstressed to failure at a constant cross-head displacement rate.4.3 A valid test result is considered to be one in which fiberfailure doesnt occur in the gripping region.4.4 Tensile strength is calculated from the ratio of the peakforce and the cross-sectional area of a plane perpendicular tothe fiber axis,at the fracture location or in the vicinity of thefracture location,while Youngs modulus is determined fromthe linear region of the tensile stress versus tensile strain curve.5.Significance and Use5.1 Properties determined by this test method are useful inthe evaluation of new fibers at the research and developmentlevels.Fibers with diameters up to 250 10-6m are covered bythis test method.Very short fibers(including whiskers)call forspecialized test techniques(1)3and are not covered by this testmethod.This test method may also be useful in the initialscreening of candidate fibers for applications in polymer,metalor ceramic matrix composites,and quality control purposes.Because of their nature,ceramic fibers do not have a uniquestrength,but rather,a distribution of strengths.In most caseswhen the strength of the fibers is controlled by one populationof flaws,the distribution of fiber strengths can be describedusing a two-parameter Weibull distribution,although otherdistributions have also been suggested(2,3).This test methodconstitutes a methodology to obtain the strength of a singlefiber.For the purpose of determining the parameters of the1This test method is under the jurisdiction of ASTM Committee C28 onAdvanced Ceramics and is the direct responsibility of Subcommittee C28.07 onCeramic Matrix Composites.Current edition approved Aug.15,2014.Published October 2014.Originallyapproved in 2003.Last previous edition approved in 2013 as C1557 03(2013).DOI:10.1520/C1557-14.2For 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.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 distribution of fiber strengths it is recommended to follow thistest method in conjunction with Practice C1239.6.Interferences6.1 The test environment may have an influence on themeasured tensile strength of fibers.In particular,the behaviorof fibers susceptible to slow crack growth fracture will bestrongly influenced by test environment and testing rate(4).Te