ASTM D6641 D6641M-2001e1 Standard Test Method for Determining the Compressive Properties of Polymer Matrix Composite Laminates Using a Combined Loading Compression (CLC) Test Fixtu.pdf

1、Designation: D 6641/D 6641M 01e1Standard Test Method forDetermining the Compressive Properties of Polymer MatrixComposite Laminates Using a Combined LoadingCompression (CLC) Test Fixture1This standard is issued under the fixed designation D 6641/D 6641M; the number immediately following the designat

2、ion indicates theyear of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEThe designation, D 6641/D 6641M, was ed

3、itorially corrected to be a dual standard in December 2001.1. Scope1.1 This test method establishes a procedure for determiningthe compressive strength and stiffness properties of polymermatrix composite materials using a combined loading compres-sion (CLC) (1)2or comparable test fixture. This test

4、method isapplicable to general flat laminates that are balanced andsymmetric and contain at least one 0 ply. The standardspecimen is untabbed, and, thus, for strength determination, thelaminate is limited to a maximum of 50 % 0 plies, orequivalent (see 6.4).1.2 The compressive force is introduced in

5、to the specimenby combined end- and shear-loading. In comparison, TestMethod D 3410/D 3410M is a pure shear-loading compressiontest method and Test Method D 695 is a pure end-loading testmethod.1.3 Unidirectional (0 ply orientation) composites can betested to determine unidirectional composite modul

6、us andPoissons ratio, but not compressive strength.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. Within the test theinch-pound units are shown in brackets. The values stated ineach system are not exact equivalents; therefore, each systemmust b

7、e used independently of the other. Combining valuesfrom the two systems may result in nonconformance with thestandard.NOTE 1Additional procedures for determining the compressive prop-erties of polymer matrix composites may be found in Test MethodsD 3410/D 3410M, D 5467, and D 695.1.5 This standard d

8、oes 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM St

9、andards:D 695 Test Method for Compressive Properties of RigidPlastics3D 883 Terminology Relating to Plastics3D 3410/D 3410M Test Method for Compressive Propertiesof Polymer Matrix Composite Materials with UnsupportedGage Section by Shear Loading4D 3878 Terminology for Composite Materials4D 5467 Test

10、 Method for Compressive Properties of Unidi-rectional Polymer Matrix Composites Using a SandwichBeam4D 5687/D 5687M Guide for Preparation of Flat CompositePanels with Processing Guidelines for Specimen Prepara-tion4E4 Practices for Force Verification of Testing Machines5E6 Terminology Relating to Me

11、thods of Mechanical Test-ing5E 122 Practice for Calculating Sample Size to Estimate,with a Specified Tolerable Error, the Average for a Char-acteristic of a Lot or Process6E 132 Test Method for Poissons Ratio at Room Tempera-ture5E 177 Practice for Use of the Terms Precision and Bias inASTM Test Met

12、hods6E 456 Terminology Relating to Quality and Statistics6E 1309 Guide for Identification of Fiber-Reinforced Poly-mer Matrix Composite Materials in Databases4E 1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases41This test method is under the jurisdict

13、ion of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.04 onLamina and Laminate Test Methods.Current edition approved March 10, 2001. Published May 2001.2Boldface numbers in parentheses refer to the list of references at the end of thistest method.3Annua

14、l Book of ASTM Standards, Vol 08.01.4Annual Book of ASTM Standards, Vol 15.03.5Annual Book of ASTM Standards, Vol 03.01.6Annual Book of ASTM Standards, Vol 14.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.E 1471 Guide for Identi

15、fication of Fibers, Fillers, and CoreMaterials in Computerized Material Property Databases42.2 ASTM Adjunct:Combined Loading Compression (CLC) Test Fix-ture, D 664172.3 Other Documents:8ANSI Y14.5-1999, “Dimensioning and TolerancingIncludes Inch and Metric”ANSI B46.1-1995, “Surface Texture (Surface

16、Roughness,Waviness and Lay)”3. Terminology3.1 DefinitionsTerminology D 3878 defines terms relatingto high-modulus fibers and their composites. TerminologyD 883 defines terms relating to plastics. Terminology E6defines terms relating to mechanical testing. TerminologyE 456 and Practice E 177 define t

17、erms relating to statistics. Inthe event of a conflict between terms, Terminology D 3878shall have precedence over the other Terminology standards.3.2 Symbols:Across-sectional area of specimen in gage sectionByface-to-face percent bending in specimenBFback-out factorCVsample coefficient of variation

18、 in percentEclaminate compressive modulusFculaminate ultimate compressive strengthFcu0pliescompressive stress in 0 plies at laminate failureFcrEuler buckling stressGxzthrough-thickness shear modulus of laminateG12in-plane shear modulus of the 0 pliesG13,G23through-thickness shear moduli of the 0 pl

19、ieshspecimen thicknessImoment of inertia of specimen cross sectionlgspecimen gage lengthnnumber of specimensPload carried by test specimenPfload carried by test specimen at failuresas used in a lay-up code, denotes that the preceding plydescription for the laminate is repeated symmetrically aboutits

20、 midplanesn-1sample standard deviationV0volume fraction of 0 plies in laminateV90volume fraction of 90 plies in laminatewspecimen gage widthxsample mean (average)ximeasured or derived propertyeindicated normal strain from strain transducerexlaminate axial straineylaminate in-plane transverse straine

21、1,e2strain gage readingsvxyccompressive Poissons ratio4. Summary of Test Method4.1 A test fixture such as that shown in Figs. 1 and 2,oranycomparable fixture, can be used to test the untabbed, straight-sided composite specimen of rectangular cross section shownschematically in Fig. 3. A typical spec

22、imen is 140 mm 5.5 in.long and 12 mm 0.5 in. wide, having an unsupported (gage)length of 12 mm 0.5 in. when installed in the fixture. A gagelength between 12 mm and 25 mm 1.0 in. is acceptable,subject to specimen buckling considerations (see 8.2). This12-mm gage length provides sufficient space to i

23、nstall bondedstrain gages when they are required. The fixture, whichsubjects the specimen to combined end- and shear-loading, isitself loaded in compression between flat platens in a universaltesting machine. Load-strain data are collected until failureoccurs (or until a specified strain level is ac

24、hieved if onlycompressive modulus or Poissons ratio, or both, is to bedetermined, and not the complete stress-strain curve to failure).7A detailed drawing for the fabrication of the test fixture shown in Figs. 1 and2 is available from ASTM Headquarters. Order Adjunct No. ADJD6641.8Available from Ame

25、rican National Standards Institute, 25 W. 43rd St., 4thFloor, New York, NY 10036.FIG. 1 Photograph of a Typical Combined Loading Compression (CLC) Test FixtureD 6641/D 6641M 01e125. Significance and Use5.1 This test method is designed to produce compressiveproperty data for material specifications,

26、research and devel-opment, quality assurance, and structural design and analysis.When specific laminates are tested (primarily of the 90/0nsfamily, although other laminates containing a maximum of50 % 0 plies can be used), the data are frequently used to“back out” 0 ply strength, using laminate theo

27、ry to calculate a0 unidirectional lamina strength (1, 2). Factors that influencethe compressive response include: type of material, methods ofmaterial preparation and lay-up, specimen stacking sequence,specimen preparation, specimen conditioning, environment oftesting, speed of testing, time at temp

28、erature, void content, andvolume percent reinforcement. Laminate properties, in the testdirection, that may be obtained from this test method include:5.1.1 Ultimate compressive strength,5.1.2 Ultimate compressive strain,5.1.3 Compressive (linear or chord) modulus of elasticity,and5.1.4 Poissons rati

29、o in compression.6. Interferences6.1 Because of partial end loading of the specimen in thistest method, it is important that the ends of the specimen bemachined parallel to each other and perpendicular to the longaxis of the coupon (see Fig. 3). Improper preparation mayresult in premature end crushi

30、ng of the specimen duringloading, excessive induced bending, or buckling, potentiallyinvalidating the test.6.2 Erroneously low laminate compressive strengths will beproduced as a result of Euler column buckling if the specimenis too thin in relation to the gage length (see 8.2). In such cases,the sp

31、ecimen thickness must be increased or the gage lengthreduced below the minimum gage length required. A practicallimit on reducing gage length is maintaining adequate space inwhich to attach strain gages. Bending or buckling, or both, canusually only be detected by the use of back-to-back straingages

32、 mounted on the faces of the specimen or by examiningthe specimen failure mode (3). Bending and buckling are notvisually obvious during the test.Note: Using standard14-in. 28 UNF screws, the bolt torque required to test most composite material specimens successfully is typically between 2.5 and 3.0

33、N-m 20and 25 in.-lb.FIG. 2 Dimensioned Sketch of a Typical Combined Loading Compression (CLC) Test FixtureD 6641/D 6641M 01e136.3 For a valid test, final failure of the specimen must occurwithin the gage section. Which failure modes are deemedacceptable will be governed by the particular material, l

34、ami-nate configuration, and application (see 10.1).6.4 Continuous-fiber-reinforced laminates having more than50 % axially oriented (0) plies may require higher thanacceptable fixture clamping forces to prevent end crushing.Therefore, such specimens are considered nonstandard. Exces-sive clamping for

35、ces induce at the ends of the gage sectionlocal stress concentrations that may produce erroneously lowstrength results (see 9.2.7).6.5 If the outermost plies of the laminate are oriented at 0,the local stress concentrations at the ends of the specimen gagesection may lead to premature failure of the

36、se primary load-bearing plies, producing erroneously low laminate strengthresults. This is particularly true for specimens with lownumbers of plies, since then the outer plies represent asignificant fraction of the total number of plies (1).6.6 The compressive strength and stiffness properties ofoth

37、er laminate configurations may also be determined usingthis same untabbed specimen test method, subject to somelimitations (1). One limitation is that the fixture clampingforces induced by the applied bolt torques required to success-fully fail the composite before specimen end crushing must notindu

38、ce significant stress concentrations at the ends of the gagesection (4). Such stress concentrations will degrade the mea-sured compressive strength. For example, testing an untabbedhigh-strength unidirectional composite is likely to be unsuc-cessful because of the excessive clamping forces required

39、toprevent specimen end crushing, whereas a lower strengthunidirectional composite may be successfully tested usingacceptable clamping forces. The use of a tabbed specimen toincrease the bearing area at the specimen ends is possible,although nonstandard, and not desirable as tabs also inducestress co

40、ncentrations at the ends of the gage section (1, 5).Anuntabbed thickness-tapered specimen, although nonstandard,has also been used to test successfully high-strength unidirec-tional composites (5).6.7 In multidirectional laminates, edge effects can affect themeasured strength and modulus of the lami

41、nate.7. Apparatus and Supplies7.1 Micrometers and CalipersA micrometer having asuitable-size diameter ball-interface on irregular surfaces suchas the bag-side of a laminate, and a flat anvil interface onmachined edges or very smooth tooled surfaces, shall be used.Notes:(1) The specimen ends must be

42、parallel to each other within 0.03 mm 0.001 in. and also perpendicular to the longitudinal axis of the specimen within 0.03 0.001 in.(2) Nominal specimen thickness can be varied, but must be uniform. Thickness irregularities (for example, thickness taper or surface imperfections) shall not exceed0.0

43、3 mm 0.001 in. across the specimen width or 0.06 mm 0.002 in. along the specimen length.(3) The faces of the specimen may be lapped slightly to remove any local surface imperfections and irregularities, thus providing flatter surfaces for more uniformgripping by the fixture.FIG. 3 Typical Test Speci

44、men ConfigurationD 6641/D 6641M 01e14A caliper of suitable size can also be used on machined edgesor very smooth tooled surfaces. The accuracy of these instru-ments shall be suitable for reading to within 1 % of the samplelength, width and thickness. For typical specimen geometries,an instrument wit

45、h an accuracy of 62.5 m 60.0001 in. isdesirable for thickness and width measurement, while aninstrument with an accuracy of 625 m 60.001 in. isdesirable for length measurements.7.2 Torque WrenchCalibrated within the torque rangerequired.7.3 Testing MachineA calibrated testing machine shall beused wh

46、ich can be operated at constant crosshead speed overthe specified range. The test machine mechanism shall beessentially free from inertial lag at the crosshead speedsspecified. The machine shall be equipped with an appropriateload-measuring device (for example, a load cell). The accuracyof the test

47、machine shall be in accordance with Practices E4.7.4 Environmental ChamberA chamber capable of en-closing the test fixture and specimen while they are mounted inthe testing machine, and capable of achieving the specifiedheating/cooling rates, test temperatures, and environments,shall be used when no

48、nambient conditions are required duringtesting.7.5 Compression FixtureA test fixture such as that shownin Figs. 1 and 2, or a comparable fixture, shall be used. Thefixture shown introduces a controllable ratio of end loading toshear loading into the specimen, by controlling the torqueapplied to the

49、clamping screws.7.6 Strain-Indicating DeviceLongitudinal strain shall besimultaneously measured on opposite faces of the specimen toallow for a correction as a result of any bending of thespecimen, and to enable detection of Euler (column) buckling.Back-to-back strain measurement shall be made for all fivespecimens when the minimum number of specimens allowedby this test method are tested. If more than five specimens areto be tested, then a single strain-indicating device may be usedfor the number