ASTM D638-2008 Standard Test Method for Tensile Properties of Plastics.pdf

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1、Designation: D 638 08Standard Test Method forTensile Properties of Plastics1This standard is issued under the fixed designation D 638; 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 parenthes

2、es indicates the year of last reapproval. Asuperscript epsilon (e) 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 This test method covers the determination of the tensileproperties of u

3、nreinforced and reinforced plastics in the formof standard dumbbell-shaped test specimens when tested underdefined conditions of pretreatment, temperature, humidity, andtesting machine speed.1.2 This test method can be used for testing materials of anythickness up to 14 mm (0.55 in.). However, for t

4、estingspecimens in the form of thin sheeting, including film less than1.0 mm (0.04 in.) in thickness, Test Methods D 882 is thepreferred test method. Materials with a thickness greater than14 mm (0.55 in.) must be reduced by machining.1.3 This test method includes the option of determiningPoissons r

5、atio at room temperature.NOTE 1This test method and ISO 527-1 are technically equivalent.NOTE 2This test method is not intended to cover precise physicalprocedures. It is recognized that the constant rate of crosshead movementtype of test leaves much to be desired from a theoretical standpoint, that

6、wide differences may exist between rate of crosshead movement and rateof strain between gage marks on the specimen, and that the testing speedsspecified disguise important effects characteristic of materials in theplastic state. Further, it is realized that variations in the thicknesses of testspeci

7、mens, which are permitted by these procedures, produce variations inthe surface-volume ratios of such specimens, and that these variations mayinfluence the test results. Hence, where directly comparable results aredesired, all samples should be of equal thickness. Special additional testsshould be u

8、sed where more precise physical data are needed.NOTE 3This test method may be used for testing phenolic moldedresin or laminated materials. However, where these materials are used aselectrical insulation, such materials should be tested in accordance withTest Methods D 229 and Test Method D 651.NOTE

9、 4For tensile properties of resin-matrix composites reinforcedwith oriented continuous or discontinuous high modulus 20-GPa3.0 3 106-psi) fibers, tests shall be made in accordance with TestMethod D 3039/D 3039M.1.4 Test data obtained by this test method are relevant andappropriate for use in enginee

10、ring design.1.5 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationonly.1.6 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 estab

11、lish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 229 Test Methods for Rigid Sheet and Plate MaterialsUsed for Electrical InsulationD 412 Test Methods for Vulcanized Rubber and Thermo-pla

12、stic ElastomersTensionD 618 Practice for Conditioning Plastics for TestingD 651 Method of Test for Tensile Strength of MoldedElectrical Insulating Material3D 882 Test Method for Tensile Properties of Thin PlasticSheetingD 883 Terminology Relating to PlasticsD 1822 Test Method for Tensile-Impact Ener

13、gy to BreakPlastics and Electrical Insulating MaterialsD 3039/D 3039M Test Method for Tensile Properties ofPolymer Matrix Composite MaterialsD 4000 Classification System for Specifying Plastic Mate-rialsD 4066 Classification System for Nylon Injection and Ex-trusion Materials (PA)D 5947 Test Methods

14、 for Physical Dimensions of SolidPlastics SpecimensE4 Practices for Force Verification of Testing MachinesE83 Practice for Verification and Classification of Exten-someter SystemsE 132 Test Method for Poissons Ratio at Room Tempera-tureE 691 Practice for Conducting an Interlaboratory Study toDetermi

15、ne the Precision of a Test Method2.2 ISO Standard:41This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.Current edition approved April 1, 2008. Published May 2008. Originallyapproved in 1941. Las

16、t previous edition approved in 2003 as D 638 - 03.2For 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.3Withdrawn4

17、Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United

18、States.ISO 527-1 Determination of Tensile Properties3. Terminology3.1 DefinitionsDefinitions of terms applying to this testmethod appear in Terminology D 883 and Annex A2.4. Significance and Use4.1 This test method is designed to produce tensile propertydata for the control and specification of plas

19、tic materials. Thesedata are also useful for qualitative characterization and forresearch and development. For many materials, there may be aspecification that requires the use of this test method, but withsome procedural modifications that take precedence whenadhering to the specification. Therefor

20、e, it is advisable to referto that material specification before using this test method.Table 1 in Classification D 4000 lists the ASTM materialsstandards that currently exist.4.2 Tensile properties may vary with specimen preparationand with speed and environment of testing. Consequently,where preci

21、se comparative results are desired, these factorsmust be carefully controlled.4.2.1 It is realized that a material cannot be tested withoutalso testing the method of preparation of that material. Hence,when comparative tests of materials per se are desired, thegreatest care must be exercised to ensu

22、re that all samples areprepared in exactly the same way, unless the test is to includethe effects of sample preparation. Similarly, for referee pur-poses or comparisons within any given series of specimens,care must be taken to secure the maximum degree of unifor-mity in details of preparation, trea

23、tment, and handling.4.3 Tensile properties may provide useful data for plasticsengineering design purposes. However, because of the highdegree of sensitivity exhibited by many plastics to rate ofstraining and environmental conditions, data obtained by thistest method cannot be considered valid for a

24、pplications involv-ing load-time scales or environments widely different fromthose of this test method. In cases of such dissimilarity, noreliable estimation of the limit of usefulness can be made formost plastics. This sensitivity to rate of straining and environ-ment necessitates testing over a br

25、oad load-time scale (includ-ing impact and creep) and range of environmental conditions iftensile properties are to suffice for engineering design pur-poses.NOTE 5Since the existence of a true elastic limit in plastics (as inmany other organic materials and in many metals) is debatable, thepropriety

26、 of applying the term “elastic modulus” in its quoted, generallyaccepted definition to describe the “stiffness” or “rigidity” of a plastic hasbeen seriously questioned. The exact stress-strain characteristics of plasticmaterials are highly dependent on such factors as rate of application ofstress, t

27、emperature, previous history of specimen, etc. However, stress-strain curves for plastics, determined as described in this test method,almost always show a linear region at low stresses, and a straight linedrawn tangent to this portion of the curve permits calculation of an elasticmodulus of the usu

28、ally defined type. Such a constant is useful if itsarbitrary nature and dependence on time, temperature, and similar factorsare realized.5. Apparatus5.1 Testing MachineA testing machine of the constant-rate-of-crosshead-movement type and comprising essentiallythe following:5.1.1 Fixed MemberA fixed

29、or essentially stationarymember carrying one grip.5.1.2 Movable MemberA movable member carrying asecond grip.5.1.3 GripsGrips for holding the test specimen betweenthe fixed member and the movable member of the testingmachine can be either the fixed or self-aligning type.5.1.3.1 Fixed grips are rigid

30、ly attached to the fixed andmovable members of the testing machine. When this type ofgrip is used extreme care should be taken to ensure that the testspecimen is inserted and clamped so that the long axis of thetest specimen coincides with the direction of pull through thecenter line of the grip ass

31、embly.5.1.3.2 Self-aligning grips are attached to the fixed andmovable members of the testing machine in such a manner thatthey will move freely into alignment as soon as any load isapplied so that the long axis of the test specimen will coincidewith the direction of the applied pull through the cen

32、ter line ofthe grip assembly. The specimens should be aligned as per-fectly as possible with the direction of pull so that no rotarymotion that may induce slippage will occur in the grips; thereis a limit to the amount of misalignment self-aligning grips willaccommodate.5.1.3.3 The test specimen sha

33、ll be held in such a way thatslippage relative to the grips is prevented insofar as possible.Grip surfaces that are deeply scored or serrated with a patternsimilar to those of a coarse single-cut file, serrations about 2.4mm (0.09 in.) apart and about 1.6 mm (0.06 in.) deep, havebeen found satisfact

34、ory for most thermoplastics. Finer serra-tions have been found to be more satisfactory for harderplastics, such as the thermosetting materials. The serrationsshould be kept clean and sharp. Breaking in the grips mayoccur at times, even when deep serrations or abraded specimensurfaces are used; other

35、 techniques must be used in these cases.Other techniques that have been found useful, particularly withsmooth-faced grips, are abrading that portion of the surface ofthe specimen that will be in the grips, and interposing thinpieces of abrasive cloth, abrasive paper, or plastic, or rubber-coated fab

36、ric, commonly called hospital sheeting, between thespecimen and the grip surface. No. 80 double-sided abrasivepaper has been found effective in many cases. An open-meshfabric, in which the threads are coated with abrasive, has alsobeen effective. Reducing the cross-sectional area of the speci-men ma

37、y also be effective. The use of special types of grips issometimes necessary to eliminate slippage and breakage in thegrips.5.1.4 Drive MechanismA drive mechanism for impartingto the movable member a uniform, controlled velocity withrespect to the stationary member, with this velocity to beregulated

38、 as specified in Section 8.5.1.5 Load IndicatorA suitable load-indicating mecha-nism capable of showing the total tensile load carried by thetest specimen when held by the grips. This mechanism shall beessentially free of inertia lag at the specified rate of testing andD638082shall indicate the load

39、 with an accuracy of 61 % of theindicated value, or better. The accuracy of the testing machineshall be verified in accordance with Practices E4.NOTE 6Experience has shown that many testing machines now in useare incapable of maintaining accuracy for as long as the periods betweeninspection recommen

40、ded in Practices E4. Hence, it is recommended thateach machine be studied individually and verified as often as may befound necessary. It frequently will be necessary to perform this functiondaily.5.1.6 The fixed member, movable member, drive mecha-nism, and grips shall be constructed of such materi

41、als and insuch proportions that the total elastic longitudinal strain of thesystem constituted by these parts does not exceed 1 % of thetotal longitudinal strain between the two gage marks on the testspecimen at any time during the test and at any load up to therated capacity of the machine.5.1.7 Cr

42、osshead Extension IndicatorA suitable extensionindicating mechanism capable of showing the amount ofchange in the separation of the grips, that is, crossheadmovement. This mechanism shall be essentially free of inertiallag at the specified rate of testing and shall indicate thecrosshead movement wit

43、h an accuracy of 610 % of theindicated value.5.2 Extension Indicator (extensometer)A suitable instru-ment shall be used for determining the distance between twodesignated points within the gage length of the test specimen asthe specimen is stretched. For referee purposes, the extensom-eter must be s

44、et at the full gage length of the specimen, asshown in Fig. 1. It is desirable, but not essential, that thisinstrument automatically record this distance, or any change init, as a function of the load on the test specimen or of theelapsed time from the start of the test, or both. If only the latteri

45、s obtained, load-time data must also be taken. This instrumentshall be essentially free of inertia at the specified speed oftesting. Extensometers shall be classified and their calibrationperiodically verified in accordance with Practice E83.5.2.1 Modulus-of-Elasticity MeasurementsFor modulus-of-ela

46、sticity measurements, an extensometer with a maximumstrain error of 0.0002 mm/mm (in./in.) that automatically andcontinuously records shall be used. An extensometer classifiedby Practice E83 as fulfilling the requirements of a B-2classification within the range of use for modulus measure-ments meets

47、 this requirement.5.2.2 Low-Extension MeasurementsFor elongation-at-yield and low-extension measurements (nominally 20 % orless), the same above extensometer, attenuated to 20 % exten-sion, may be used. In any case, the extensometer system mustmeet at least Class C (Practice E83) requirements, which

48、include a fixed strain error of 0.001 strain or 61.0 % of theindicated strain, whichever is greater.5.2.3 High-Extension MeasurementsFor making mea-surements at elongations greater than 20 %, measuring tech-niques with error no greater than 610 % of the measured valueare acceptable.5.3 MicrometersAp

49、paratus for measuring the width andthickness of the test specimen shall comply with the require-ments of Test Method D 5947.6. Test Specimens6.1 Sheet, Plate, and Molded Plastics:6.1.1 Rigid and Semirigid PlasticsThe test specimen shallconform to the dimensions shown in Fig. 1. The Type Ispecimen is the preferred specimen and shall be used wheresufficient material having a thickness of 7 mm (0.28 in.) or lessis available. The Type II specimen may be used when amaterial does not break in the narrow section with the preferredType I specimen. The Type V specimen sh