ASTM D7269-2008 781 Standard Test Methods for Tensile Testing of Aramid Yarns.pdf

1、Designation: D 7269 08Standard Test Methods forTensile Testing of Aramid Yarns1This standard is issued under the fixed designation D 7269; 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 paren

2、theses indicates the year of last reapproval. Asuperscript 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 cord may be

3、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 These test methods show the values in both SI andinch-pound units. SI units is the technically correct nam

4、e forthe system of metric units known as the International System ofUnits. Inch-pound units is the technically correct name for thecustomary units used in the United States. The values stated ineither acceptable metric units or other units shall be regardedseparately as standard. The values expresse

5、d in each systemmay not be exact equivalents; therefore, each system must beused independently of each other, without combining values inany way.1.3 This standard includes the following test methods:SectionBreaking Strength (Force) 11Breaking Tenacity 12Breaking Toughness 17Elongation at Break 13For

6、ce 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 standard to establish appro-priate safety and health practices and dete

7、rmine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D76 Specification for Tensile Testing Machines for TextilesD 123 Terminology Relating to TextilesD 885 Test Methods for Tire Cords, Tire Cord Fabrics, andIndustrial Filament Yarns Made from Man

8、ufacturedOrganic-Base FibersD 1776 Practice for Conditioning and Testing TextilesD 1907 Test Method for Linear Density of Yarn (YarnNumber) by the Skein MethodD 1909 Standard Table of Commercial Moisture Regainsfor Textile FibersD 2258 Practice for Sampling Yarn for TestingD 4848 Terminology Related

9、 to Force, Deformation andRelated Properties of TextilesD 6477 Terminology Relating to Tire Cord, Bead Wire,Hose Reinforcing Wire, and Fabrics3. Terminology3.1 Definitions:3.1.1 For definitions of terms relating to tire cord and tirecord fabrics, refer to Terminology D 6477.3.1.1.1 The following ter

10、ms are relevant to this standard:cord, cord twist, dip, dip pickup, in a textile cord or fabric,industrial yarn, moisture equilibrium for testing, for industrialyarns and tire cords, pneumatic tire, single twist, standardatmosphere for testing textiles, tabby sample, tire, and tire cordfabric.3.1.2

11、For definitions of terms related to force and deforma-tion in textiles, refer to Terminology D 4848.3.1.2.1 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 specifie

12、d elongation (FASE), initial modulus, tensilestrength, and work-to-break.3.1.3 For definitions of other terms related to textiles, referto Terminology D 123.3.1.3.1 The following terms are relevant to this standard:fabric and growth.4. Summary of Test Method4.1 These test methods are used to determi

13、ne the tensileproperties of aramid yarns or cords.4.2 Aconditioned or oven-dried 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 wo

14、rk-to-break are calculated from the force-elongation1These test methods are under the jurisdiction of ASTM Committee D13 onTextiles and are the direct responsibility of Subcommittee D13.19 on Tire Cord andFabrics.Current edition approved Aug. 1, 2008. Published October 2008. Originallyapproved in 20

15、06. Last previous edition approved in 2007 as D 726907.2For 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.1Copyr

16、ight ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.curve. The output of a constant-rate-of-extension (CRE) tensiletesting machine can be connected with electronic recording andcomputing equipment, which may be programmed to calculateand print

17、 the test results of tensile properties of interest.5. Significance and Use5.1 The levels of tensile properties obtained when testingaramid yarns and tire cords are dependent on the age andhistory of the specimen and on the specific conditions usedduring the test. Among these conditions are rate of

18、stretching,type of clamps, gage length of specimen, temperature andhumidity of the atmosphere, rate of airflow across the speci-men, and temperature and moisture content of the specimen.Testing conditions accordingly are specified precisely to obtainreproducible test results on a specific sample.5.2

19、 Because the force-bearing ability of a reinforced rubberproduct is 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 reinforcedrubber products. When needed to compare intrinsic stre

20、ngthcharacteristics of yarns or cords of different sizes or differenttypes of fiber, breaking tenacity is very useful because, for agiven type of fiber, breaking force is approximately propor-tional to linear density.5.3 Elongation of yarn or cord is taken into consideration inthe design and enginee

21、ring of reinforced rubber productsbecause of its effect on uniformity of the finished product andits dimensional 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

22、 cord into a rubberproduct.5.5 Modulus is a measure of the resistance 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 spe

23、cified force, initial modulus is thevalue most commonly used.5.6 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,

24、 although the precedingparameters are related to the performance 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 perfor

25、mance of a textile reinforcedproduct in terms of the reinforcing 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 co

26、mpetent statistical assis-tance. As a minimum, test samples should 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 estab

27、lished test values may beused for this purpose. The test results 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 mu

28、st be adjusted in consideration of the knownbias.6. Apparatus6.1 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. Thetesting m

29、achine shall be equipped with an autographic recorder(rectilinear 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 tensile

30、testing equipment.6.1.1 ClampsBollard type clamps, in which the 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

31、 of 3.14 rad(180) is recommended for yarns with a linear density up to10 000 decitex (9000 denier). For linear densities above 10 000decitex (9000 denier), clamps with a wrap angle of 4.71 rad(270) is required to prevent slippage.6.1.1.1 Clamps shall grip the test specimen without spuriousslippage o

32、r damage to the test specimen which can result in jawbreaks. The clamps 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/orspec

33、imen failure in the clamping zone.FIG. 1 Principle of Bollard Type ClampsD72690826.1.2 Gauge LengthThe gauge length shall 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

34、travel rate in mm/min (in./min) of50 % of the nominal gauge length in millimeters (inches) of thespecimen for para-aramids; 100 % of the nominal gauge lengthin millimeters (inches) of the specimen for meta-aramids.7. Sampling7.1 Yarn:7.1.1 PackagesFor acceptance testing, sample each lot asdirected i

35、n Practice D 2258. 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 industrial yarns and tire cords. Take the number ofspecimens f

36、or testing specified for the specific property mea-surement to be made.7.1.2 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 is a question or disagr

37、eementregarding 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 unit in a moisture-p

38、roofpolyethylene bag or other moisture-proof container to protectthe samples from atmospheric changes until ready to conditionthe samples in the atmosphere for testing industrial yarns andtire cords. Take the number of specimens for testing specifiedfor the specific property measurement to be made.7

39、.2 Cord:7.2.1 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

40、 alot 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 a

41、llphysical 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.7.2.2 Preparation of SamplesRemove and

42、discard a mini-mum of 25 m (25 yd) from the outside of the package beforetaking the sample or any specimens. If specimens are 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 sam

43、ple is collected asa loosely wound package, or in the form of a skein, someshrinkage invariably will occur, in which case, report 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 b

44、end with adiameter less than 10 times the yarn/cord thickness (or diam-eter). Place the sample in a moisture-proof polyethylene bag orother moisture-proof container to protect it from atmosphericchanges until ready to condition the sample in the testatmosphere for industrial yarns and tire cords.FIG

45、. 2 Principle of Specimen Fixing in Bollard Type JawsD72690837.3 Tire Cord Fabric:7.3.1 Number of Samples and SpecimensThe sizes of anacceptance sampling lot of tire cord fabric shall be one loomcreel of cord. Take a sample from at least one roll of fabric perlot. From each roll of tire cord fabric,

46、 take the number ofspecimens as specified in the test method for each property tobe measured.7.3.2 Size of SampleTake a sample equal to the length ofcord between the regular tabby woven at the end of the roll anda special tabby woven a short distance from the end when theroll of fabric is manufactur

47、ed. For rolls that do not have aspecial woven tabby, improvise a tabby by the use of gummedtape or strips of cemented fabric applied across a section of thecord fabric to give a tabby sample length at least 0.5-m (18-in.)long and at least one tenth of the roll width wide.7.3.3 Preparation of Samples

48、Cut the warp cords of thefabric along the center line of the special tabby for a distanceequal to the width of the sample. If this distance is less than thefull width of the fabric, cut the filling yarns of the sample andof the special and regular tabbies in the direction parallel withthe warp cords

49、. The resulting section of cord fabric is the tabbysample. Attach the tabby sample to a piece of cardboard orfiberboard, the length of which shall be equal to at least thelength of the cord warp between tabbies. Fold the tabbyportions of the sample over each end of the board, and securethe sample to the board with pressure-sensitive tape or staples.Use care to avoid contact of tape or staples with the area to betested. Handle the sample carefully, and hold it under sufficienttension in the warp direction to prevent the cords from kinking.Discard any specimen subjected to