1、Designation: D7269/D7269M 11Standard Test Methods forTensile Testing of Aramid Yarns1This standard is issued under the fixed designation D7269/D7269M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year of last revision. A num
2、ber in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the tensile testing of aramidyarns, cords twisted from such yarns, and fabrics woven fromsuch cords. The yarn or
3、cord may be wound on cones, tubes,bobbins, spools, or beams; may be woven into fabric; or maybe in some other form. The methods include testing procedureonly and include no specifications or tolerances.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as stand
4、ard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.3 This standard includes the following test methods:SectionBreaking Strength (Force
5、) 11Breaking Tenacity 12Breaking Toughness 17Elongation at Break 13Force at Specified Elongation (FASE) 14Linear Density 10Modulus 15Work-to-Break 161.4 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 s
6、tandard 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:2D76 Specification for Tensile Testing Machines for TextilesD123 Terminology Relating to TextilesD1776 Practice for Conditio
7、ning and Testing TextilesD1907 Test Method for Linear Density of Yarn (YarnNumber) by the Skein MethodD1909 Standard Table of Commercial Moisture Regains forTextile FibersD2258 Practice for Sampling Yarn for TestingD4848 Terminology Related to Force, Deformation andRelated Properties of TextilesD658
8、7 Test Method for Yarn Number Using AutomaticTester3. Terminology3.1 Definitions:3.1.1 slippage, nwith tensile testing, insufficient quality ofclamping, resulting in movement of the test material throughthe total clamping surface. This can be visualized by themovement of markers at the clamp exit, o
9、r by sudden changesin the strain-modulus curves (1st derivative of the strain-stresscurve).3.1.2 zero twist, ntwistless, devoid of twist.3.2 The following terms are relevant to this standard:industrial yarn, moisture equilibrium for testing, aramid, zerotwist, standard atmosphere for testing textile
10、s.3.3 For definitions of terms related to force and deformationin textiles, refer to Terminology D4848.3.4 The following terms are relevant to this standard:breaking force, breaking strength, breaking tenacity, breakingtoughness, chord modulus in a stress-strain curve, elongation,force at specified
11、elongation (FASE), initial modulus, tensilestrength, and work-to-break.3.5 For definitions of other terms related to textiles, refer toTerminology D123.4. Summary of Test Method4.1 These test methods are used to determine the tensileproperties of aramid yarns or cords.4.2 A conditioned or oven-dried
12、 specimen of aramid yarn orcord is clamped in a tensile testing machine and then stretchedor loaded until broken. Breaking force, elongation, and force atspecified elongation (FASE) are determined directly. Modulusand work-to-break are calculated from the force-elongationcurve. The output of a const
13、ant-rate-of-extension (CRE) tensiletesting machine can be connected with electronic recording and1These test methods are under the jurisdiction of ASTM Committee D13 onTextiles and are the direct responsibility of Subcommittee D13.19 on IndustrialFibers and Metallic Reinforcements.Current edition ap
14、proved May 1, 2011. Published June 2011. Originallyapproved in 2006. Last previous edition approved in 2010 as D7269/D7269M10.DOI: 10.1520/D7269_D7269M-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM
15、Standards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United Sputing equipment, which may be programmed to calculateand print the test results of tensile prope
16、rties of interest.5. Significance and Use5.1 The levels of tensile properties obtained when testingaramid yarns and cords are dependent on the age and history ofthe specimen and on the specific conditions used during thetest. Among these conditions are rate of stretching, type ofclamps, gage length
17、of specimen, temperature and humidity ofthe atmosphere, rate of airflow across the specimen, andtemperature and moisture content of the specimen. Testingconditions accordingly are specified precisely to obtain repro-ducible test results on a specific sample.5.2 Because the force-bearing ability of a
18、 reinforced productis related to the strength of the yarn or cord used as areinforcing material, breaking strength is used in engineeringcalculations when designing various types of textile reinforcedproducts. When needed to compare intrinsic strength charac-teristics of yarns or cords of different
19、sizes or different types offiber, breaking tenacity is very useful because, for a given typeof fiber, breaking force is approximately proportional to lineardensity.5.3 Elongation of yarn or cord is taken into consideration inthe design and engineering of reinforced products because ofits effect on u
20、niformity of the finished product and its dimen-sional stability during service.5.4 The FASE is used to monitor changes in characteristicsof the textile material during the various stages involved in theprocessing and incorporation of yarn or cord into a product.5.5 Modulus is a measure of the resis
21、tance of yarn or cord toextension as a force is applied. It is useful for estimating theresponse of a textile reinforced structure to the application ofvarying forces and rates of stretching. Although modulus maybe determined at any specified force, initial modulus is thevalue most commonly used.5.6
22、 Work-to-break is dependent on the relationship of forceto elongation. It is a measure of the ability of a textile structureto absorb mechanical energy. Breaking toughness is work-to-break per unit mass.5.7 It should be emphasized that, although the precedingparameters are related to the performance
23、 of a textile-reinforced product, the actual configuration of the product issignificant. Shape, size, and internal construction also can haveappreciable effect on product performance. It is not possible,therefore, to evaluate the performance of a textile reinforcedproduct in terms of the reinforcing
24、 material alone.5.8 If there are differences of practical significance betweenreported test results for two laboratories (or more), compara-tive tests should be performed to determine if there is astatistical bias between them, using competent statistical assis-tance. As a minimum, test samples shou
25、ld be used that are ashomogeneous as possible, that are drawn from the materialfrom which the disparate test results were obtained, and thatare randomly assigned in equal numbers to each laboratory fortesting. Other materials with established test values may beused for this purpose. The test results
26、 from the two laboratoriesshould be compared using a statistical test for unpaired data, ata probability level chosen prior to the testing series. If a bias isfound, either its cause must be found and corrected, or futuretest results must be adjusted in consideration of the knownbias.6. Apparatus6.1
27、 Tensile Testing MachineA single-strand tensile testingmachine of the constant rate of extension (CRE) type. Thespecifications and methods of calibration and verification ofthese machines shall conform to Specification D76. The testingmachine shall be equipped with an autographic recorder(rectilinea
28、r coordinates preferred). It is permissible to usetensile testing machines that have a means for calculating anddisplaying the required results without the use of an auto-graphic recorder. It is also permissible to use automated tensiletesting equipment.6.1.1 ClampsBollard type clamps, in which the
29、specimenis gripped between plane-faced jaws and then makes a partialturn (wrap angle) around a curved extension (or other type ofsnubbing device) of one jaw before passing to the other similarclamp (see Fig. 1). Clamps with a wrap angle of 3.14 rad180 are recommended for yarns with a linear density
30、up to10 000 decitex 9000 denier. For linear densities above 10 000decitex 9000 denier, clamps with a wrap angle of 4.71 rad270 are required to prevent slippage.6.1.1.1 Clamps shall grip the test specimen without spuriousslippage or damage to the test specimen which can result in jawbreaks. The clamp
31、s shall maintain constant gripping conditionsduring the test by means of pneumatic or hydraulic clamps. Thesurface of the jaws in contact with the specimen shall be of amaterial and configuration that minimizes slippage and/orspecimen failure in the clamping zone.6.1.2 Gauge LengthThe gauge length s
32、hall be the totallength of yarn measured between the clamping point A of thefirst clamp and the point B of the second clamp in the startingposition (see Fig. 2).6.1.3 Use a crosshead travel rate in mm/min in./min of50 % of the nominal gauge length in millimeters inches of thespecimen for para-aramid
33、s; 100 % of the nominal gauge lengthin millimeters inches of the specimen for meta-aramids.7. Sampling7.1 Remove and discard a minimum of 25 m 75 yd fromthe outside of the package before taking the sample or anyspecimens.7.2 Yarn:FIG. 1 Principle of Bollard Type ClampsD7269/D7269M 1127.2.1 PackagesF
34、or acceptance testing, sample each lot asdirected in Practice D2258. Place each laboratory samplingunit in a moisture-proof polyethylene bag or other moisture-proof container to protect the samples from atmosphericchanges until ready to condition the samples in the atmospherefor testing aramids. Tak
35、e the number of specimens for testingspecified for the specific property measurement to be made.7.2.2 BeamsFor acceptance testing, sample by windingyarns on a tube or spool by means of a winder using a tensionof 5 6 1 mN/tex 0.05 6 0.01 gf/den. Take the yarn from theoutside beam layers unless there
36、is a question or disagreementregarding the shipment; in this case, take the sample only afterremoving yarn from the beam to a radial depth of 6 mm 14 in.or more to minimize the effects of handling and atmosphericchanges that may have occurred during shipment or storage.Place each laboratory sampling
37、 unit in a moisture-proofpolyethylene bag or other moisture-proof container to protectthe samples from atmospheric changes until ready to conditionthe samples in the atmosphere for testing aramids. Take thenumber of specimens for testing specified for the specificproperty measurement to be made.7.3
38、Cord:7.3.1 Number of Samples and SpecimensThe size of anacceptance sampling lot of tire cord shall be not more than onetruck or rail car load or as determined by agreement betweenthe purchaser and the supplier. Take samples at random fromeach of a number of cones, tubes, bobbins, or spools within al
39、ot to be as representative as possible within practical limita-tions. Make only one observation on an individual package foreach physical property determination. Take the number ofsamples, therefore, that will be sufficient to cover the totalnumber of specimens required for the determination of allp
40、hysical properties of the tire cord. The recommended numberof specimens is included in the appropriate sections of specifictest methods covered in this standard. Where such is notspecified, the number of specimens is as agreed upon betweenbuyer and supplier.7.3.2 Preparation of SamplesIf specimens a
41、re not takendirectly from the original package, preferably wind the sampleon a tube or spool by means of a winder using a tension of 56 1 mN/tex 0.05 6 0.01 gf/den. If the sample is collected asa loosely wound package, or in the form of a skein, someshrinkage invariably will occur, in which case, re
42、port that theobserved results were determined on a relaxed sample. Usecare in handling the sample. Discard any sample subjected toany change of twist, kinking, or making any bend with adiameter less than 10 times the yarn/cord thickness (or diam-eter). Place the sample in a moisture-proof polyethyle
43、ne bag orother moisture-proof container to protect it from atmosphericchanges until ready to condition the sample in the testatmosphere for aramids.8. Conditioning8.1 Bring all specimens of yarn, cord, and fabric to moistureequilibrium for testing in the atmosphere for testing industrialyarns for at
44、 least 14 h as directed in Practice D1776.8.1.1 Standard aramid yarn shall be pre-conditioned at 45 65C 113 6 40F for 3 to 6 h, then condition per 8.1.8.1.2 The moisture equilibrium of conditioned aramid yarnsand tire cords made from such yarns can be affected by heatand humidity conditions to which
45、 the samples have beenpreviously exposed.9. Sample Preparation9.1 Because of the difficulty of securing the same tension inall the filaments and because of slippage in the clamps, variableresults may be obtained when testing zero-twist multifilamentyarns unless a small amount of twist is inserted pr
46、ior to testing.Machine twisting by means of a ring twister using steel inserttravelers is recommended. The twist tension should be approxi-mately 10 mN/tex 0.10 gf/den. If used, anti-balloon ringsmust be chromium plated. For aramid yarns the amount oftwist to be inserted depends upon the linear dens
47、ity and shall beapproximately:Linear density Twistdtex tpm180-240 230240-380 190380-500 160500-650 140650-775 125775-1050 1101050-1400 951400-2100 802100-4500 604500-7000 457000-9500 359500- 309.2 Inserting some twist in zero-twist yarns for tensiletesting has the following effects on the test resul
48、ts:9.2.1 Modestly increases breaking force; too much twistreduces breaking force,FIG. 2 Principle of Specimen Fixing in Bollard Type JawsD7269/D7269M 1139.2.2 Increases elongation at break, and9.2.3 Reduces modulus (the slope of the force-elongationcurve).9.3 Manner of inserting the twist into the y
49、arn, manually orwith a twisting machine, can influence the test results.10. Linear Density10.1 ScopeThis test method is used to determine thelinear density of yarn or cord for use in the calculation oftensile properties such as modulus and tenacity.10.2 Number of SpecimensTest five specimens of yarn orcord. This number is based on the assumption that theapplicable coefficient of variation is 1.0 % and the allowablevariation is 0.8 % of average with a probability level of 95 %.10.3 ProcedureDetermine linear density as directed inOp
