ASTM D695-2008 Standard Test Method for Compressive Properties of Rigid Plastics.pdf

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1、Designation: D 695 08Standard Test Method forCompressive Properties of Rigid Plastics1This standard is issued under the fixed designation D 695; 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

2、 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 Department of Defense.1. Scope*1.1 This test method covers the determination of the me-chanical p

3、roperties of unreinforced and reinforced rigid plas-tics, including high-modulus composites, when loaded incompression at relatively low uniform rates of straining orloading. Test specimens of standard shape are employed. Thisprocedure is applicable for a composite modulus up to andincluding 41,370

4、MPa (6,000,000 psi).1.2 The values stated in SI units are to be regarded as thestandard. The values in parentheses are for information only.NOTE 1For compressive properties of resin-matrix composites rein-forced with oriented continuous, discontinuous, or cross-ply reinforce-ments, tests may be made

5、 in accordance with Test Method D 3410/D 3410.1.3 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 regul

6、atory limitations prior to use. A specific precau-tionary statement is given in 13.1.NOTE 2This test method is technically equivalent to ISO 604.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 638 Test Method for Tensile Properties of PlasticsD 883 Te

7、rminology Relating to PlasticsD 3410/D 3410M Test Method for Compressive Propertiesof Polymer Matrix Composite Materials with UnsupportedGage Section by Shear LoadingD 4000 Classification System for Specifying Plastic Mate-rialsD 4066 Classification System for Nylon Injection and Ex-trusion Material

8、s (PA)D 5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensE4 Practices for Force Verification of Testing MachinesE83 Practice for Verification and Classification of Exten-someter SystemsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Metho

9、d3. Terminology3.1 General The definitions of plastics used in this testmethod are in accordance with Terminology D 883 unlessotherwise indicated.3.2 Definitions:3.2.1 compressive deformationthe decrease in length pro-duced in the gage length of the test specimen by a compressiveload. It is expresse

10、d in units of length.3.2.2 compressive strainthe ratio of compressive defor-mation to the gage length of the test specimen, that is, thechange in length per unit of original length along the longitu-dinal axis. It is expressed as a dimensionless ratio.3.2.3 compressive strengththe maximum compressiv

11、estress (nominal) carried by a test specimen during a compres-sion test. It may or may not be the compressive stress(nominal) carried by the specimen at the moment of rupture.3.2.4 compressive strength at failure (nominal)the com-pressive stress (nominal) sustained at the moment of failure ofthe tes

12、t specimen if shattering occurs.3.2.5 compressive stress (nominal)the compressive loadper unit area of minimum original cross section within the gageboundaries, carried by the test specimen at any given moment.It is expressed in force per unit area.3.2.5.1 DiscussionThe expression of compressive pro

13、per-ties in terms of the minimum original cross section is almostuniversally used. Under some circumstances the compressive1This 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 app

14、roved Aug. 1, 2008. Published September 2008. Originallyapproved in 1942. Last previous edition approved in 2002 as D 695 - 02a.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informatio

15、n, refer to the standards Document Summary page onthe ASTM website.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 States.properties have been expressed per unit of prevailin

16、g crosssection. These properties are called “true” compressive prop-erties.3.2.6 compressive stress-strain diagrama diagram inwhich values of compressive stress are plotted as ordinatesagainst corresponding values of compressive strain as abscis-sas.3.2.7 compressive yield pointthe first point on th

17、e stress-strain diagram at which an increase in strain occurs without anincrease in stress.3.2.8 compressive yield strengthnormally the stress at theyield point (see also section 3.2.11).3.2.9 crushing loadthe maximum compressive force ap-plied to the specimen, under the conditions of testing, thatp

18、roduces a designated degree of failure.3.2.10 modulus of elasticitythe ratio of stress (nominal) tocorresponding strain below the proportional limit of a material.It is expressed in force per unit area based on the average initialcross-sectional area.3.2.11 offset compressive yield strengththe stres

19、s at whichthe stress-strain curve departs from linearity by a specifiedpercent of deformation (offset).3.2.12 percent compressive strainthe compressive defor-mation of a test specimen expressed as a percent of the originalgage length.3.2.13 proportional limitthe greatest stress that a materialis cap

20、able of sustaining without any deviation from propor-tionality of stress to strain (Hookes law). It is expressed inforce per unit area.3.2.14 slenderness ratiothe ratio of the length of a col-umn of uniform cross section to its least radius of gyration. Forspecimens of uniform rectangular cross sect

21、ion, the radius ofgyration is 0.289 times the smaller cross-sectional dimension.For specimens of uniform circular cross section, the radius ofgyration is 0.250 times the diameter.4. Significance and Use4.1 Compression tests provide information about the com-pressive properties of plastics when emplo

22、yed under conditionsapproximating those under which the tests are made.4.2 Compressive properties include modulus of elasticity,yield stress, deformation beyond yield point, and compressivestrength (unless the material merely flattens but does notfracture). Materials possessing a low order of ductil

23、ity may notexhibit a yield point. In the case of a material that fails incompression by a shattering fracture, the compressive strengthhas a very definite value. In the case of a material that does notfail in compression by a shattering fracture, the compressivestrength is an arbitrary one depending

24、 upon the degree ofdistortion that is regarded as indicating complete failure of thematerial. Many plastic materials will continue to deform incompression until a flat disk is produced, the compressivestress (nominal) rising steadily in the process, without anywell-defined fracture occurring. Compre

25、ssive strength canhave no real meaning in such cases.4.3 Compression tests provide a standard method of obtain-ing data for research and development, quality control, accep-tance or rejection under specifications, and special purposes.The tests cannot be considered significant for engineeringdesign

26、in applications differing widely from the load-time scaleof the standard test. Such applications require additional testssuch as impact, creep, and fatigue.4.4 Before proceeding with this test method, referenceshould be made to the ASTM specification for the materialbeing tested. Any test specimen p

27、reparation, conditioning,dimensions, and testing parameters covered in the materialsspecification shall take precedence over those mentioned in thistest method. If there is no material specification, then thedefault conditions apply. Table 1 in Classification D 4000 liststhe ASTM materials standards

28、 that currently exist.5. Apparatus5.1 Testing MachineAny suitable testing machine capableof control of constant-rate-of-crosshead movement and com-prising essentially the following:5.1.1 Drive MechanismA drive mechanism for impartingto the movable cross-head member, a uniform, controlledvelocity wit

29、h respect to the base (fixed member), with thisvelocity to be regulated as specified in Section 9.5.1.2 Load IndicatorA load-indicating mechanism ca-pable of showing the total compressive load carried by the testspecimen. The mechanism shall be essentially free frominertia-lag at the specified rate

30、of testing and shall indicate theload with an accuracy of 61 % of the maximum indicatedvalue of the test (load). The accuracy of the testing machineshall be verified at least once a year in accordance withPractices E4.5.2 CompressometerA suitable instrument for determin-ing the distance between two

31、fixed points on the test specimenat any time during the test. It is desirable that this instrumentautomatically record this distance (or any change in it) as afunction of the load on the test specimen. The instrument shallbe essentially free of inertia-lag at the specified rate of loadingand shall c

32、onform to the requirements for a Class B-2extensometer as defined in Practice E83.NOTE 3The requirements for extensometers cited herein apply tocompressometers as well.5.3 Compression ToolAcompression tool for applying theload to the test specimen. This tool shall be so constructed thatloading is ax

33、ial within 1:1000 and applied through surfaces thatare flat within 0.025 mm (0.001 in.) and parallel to each otherin a plane normal to the vertical loading axis. Examples ofsuitable compression tools are shown in Fig. 1 and Fig. 2.5.4 Supporting JigA supporting jig for thin specimens isshown in Fig.

34、 3 and Fig. 4.5.5 MicrometersSuitable micrometers, reading to 0.01mm or 0.001 in. for measuring the width, thickness, and lengthof the specimens.6. Test Specimens6.1 Unless otherwise specified in the materials specifica-tions, the specimens described in 6.2 and 6.7 shall be used.These specimens may

35、be prepared by machining operationsfrom materials in sheet, plate, rod, tube, or similar form, orthey may be prepared by compression or injection molding ofthe material to be tested. All machining operations shall bedone carefully so that smooth surfaces result. Great care shallD695082be taken in ma

36、chining the ends so that smooth, flat parallelsurfaces and sharp, clean edges, to within 0.025 mm (0.001 in.)perpendicular to the long axis of the specimen, result.6.2 The standard test specimen, except as indicated in6.3-6.7, shall be in the form of a right cylinder or prism whoselength is twice it

37、s principal width or diameter. Preferredspecimen sizes are 12.7 by 12.7 by 25.4 mm (0.50 by 0.50 by1 in.) (prism), or 12.7 mm in diameter by 25.4 mm (cylinder).Where elastic modulus and offset yield-stress data are desired,the test specimen shall be of such dimensions that the slender-ness ratio is

38、in the range from 11 to 16:1. In this case, preferredspecimen sizes are 12.7 by 12.7 by 50.8 mm (0.50 by 0.50 by2 in.) (prism), or 12.7 mm in diameter by 50.8 mm (cylinder).6.3 For rod material, the test specimen shall have a diameterequal to the diameter of the rod and a sufficient length to allowa

39、 specimen slenderness ratio in the range from 11 to 16:1.6.4 When testing tubes, the test specimen shall have adiameter equal to the diameter of the tube and a length of 25.4mm (1 in.) (Note 4). For crushing-load determinations (at rightangles to the longitudinal axis), the specimen size shall be th

40、esame, with the diameter becoming the height.NOTE 4This specimen can be used for tubes with a wall thickness of1 mm (0.039 in.) or over, to inside diameters of 6.4 mm (0.25 in.) or over,and to outside diameters of 50.8 mm (2.0 in.) or less.6.5 Where it is desired to test conventional high-pressurela

41、minates in the form of sheets, the thickness of which is lessthan 25.4 mm (1 in.), a pile-up of sheets 25.4 mm square, witha sufficient number of layers to produce a height of at least 25.4mm, may be used.6.6 When testing material that may be suspected of anisot-ropy, duplicate sets of test specimen

42、s shall be prepared havingtheir long axis respectively parallel with and normal to thesuspected direction of anisotropy.6.7 Reinforced Plastics, Including High-Strength Compos-ites and High-Strength Composites and Highly OrthotropicLaminatesThe following specimens shall be used for rein-forced mater

43、ials, or for other materials when necessary tocomply with the slenderness ratio requirements or to permitattachment of a deformation-measuring device.6.7.1 For materials 3.2 mm (18 in.) and over in thickness, aspecimen shall consist of a prism having a cross section of 12.7mm (12 in.) by the thickne

44、ss of the material and a length suchthat the slenderness ratio is in the range from 11 to 16:1 (Note5).6.7.2 For materials under 3.2 mm (18 in.) thick, or whereelastic modulus testing is required and the slenderness ratiodoes not provide for enough length for attachment of acompressometer or similar

45、 device, a specimen conforming tothat shown in Fig. 5 shall be used. The supporting jig shown inFig. 3 and Fig. 4 shall be used to support the specimen duringtesting (Note 6).NOTE 5If failure for materials in the thickness range of 3.2 mm (18NOTE 1Devices similar to the one illustrated have been suc

46、cessfullyused in a number of different laboratories. Details of the device developedat the National Institute for Standards and Technology are given in thepaper byAitchinson, C. S., and Miller, J.A., “ASubpress for CompressiveTests,” NationalAdvisory Committee forAeronautics, Technical Note No.912,

47、1943.FIG. 1 Subpress for Compression TestsFIG. 2 Compression ToolFIG. 3 Support Jig for Thin SpecimenD695083in.) is by delamination rather than by the desirable shear plane fracture, thematerial may be tested in accordance with 6.7.2.NOTE 6Round-robin tests have established that relatively satisfact

48、orymeasurements of modulus of elasticity may be obtained by applying acompressometer to the edges of the jig-supported specimen.6.8 When testing syntactic foam, the standard test specimenshall be in the form of a right cylinder 25.4 mm (1 in.) indiameter by 50.8 mm (2 in.) in length.7. Conditioning7

49、.1 ConditioningCondition the test specimens at 23 62C (73.4 6 3.6F) and 50 6 10 % relative humidity for notless than 40 h prior to test in accordance with Procedure A ofPractice D 618 unless otherwise specified by contract orrelevant ASTM material specification. Reference pre-test con-ditioning, to settle disagreements, shall apply tolerances of61C (1.8F) and 62 % relative humidity.7.1.1 Note that for some hygroscopic materials, such asnylons, the material specifications (for example, ClassificationSystem D 4066) call for testing “dry as-molded