1、Designation: D6641/D6641M 161Standard Test Method forCompressive Properties of Polymer Matrix CompositeMaterials Using a Combined Loading Compression (CLC)Test Fixture1This standard is issued under the fixed designation D6641/D6641M; the number immediately following the designation indicates theyear
2、 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 () indicates an editorial change since the last revision or reapproval.1NOTEA label in Figure 3 was corrected editorially in March 2017.1.
3、 Scope1.1 This test method determines the compressive strengthand stiffness properties of polymer matrix composite materialsusing a combined loading compression (CLC) (1)2test fixture.This test method is applicable to general composites that arebalanced and symmetric. The specimen may be untabbed(Pr
4、ocedure A) or tabbed (Procedure B), as required. Onerequirement for a successful test is that the specimen ends donot crush during the test. Untabbed specimens are usuallysuitable for use with materials of low orthotropy, for example,fabrics, chopped fiber composites, and laminates with a maxi-mum o
5、f 50 % 0 plies, or equivalent (see 6.4). Materials ofhigher orthotropy, including unidirectional composites, typi-cally require tabs.1.2 The compressive force is introduced into the specimenby combined end- and shear-loading. In comparison, TestMethod D3410/D3410M is a pure shear-loading compression
6、test method and Test Method D695 is a pure end-loading testmethod.1.3 Unidirectional (0 ply orientation) composites as well asmulti-directional composite laminates, fabric composites,chopped fiber composites, and similar materials can be tested.1.4 The values stated in either SI units or inch-pound
7、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 be used independently of the other. Combining valuesfrom the two systems may result in nonconformance with
8、thestandard.NOTE 1Additional procedures for determining the compressive prop-erties of polymer matrix composites may be found in Test MethodsD3410/D3410M, D5467/D5467M, and D695.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespons
9、ibility 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 Standards:3D695 Test Method for Compressive Properties of RigidPlasticsD883 Terminology Relating to Plast
10、icsD3410/D3410M Test Method for Compressive Properties ofPolymer Matrix Composite Materials with UnsupportedGage Section by Shear LoadingD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite Materi
11、alsD5379/D5379M Test Method for Shear Properties of Com-posite Materials by the V-Notched Beam MethodD5467/D5467M Test Method for Compressive Properties ofUnidirectional Polymer Matrix Composite Materials Us-ing a Sandwich BeamD5687/D5687M Guide for Preparation of Flat CompositePanels with Processin
12、g Guidelines for Specimen Prepara-tionE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Characteristic of aLot or ProcessE132 Test Method for
13、 Poissons Ratio at Room Temperature1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.04 onLamina and Laminate Test Methods.Current edition approved Nov. 1, 2016. Published November 2016. Originallyapproved in
14、2001. Last previous edition approved in 2014 as D6641/D6641M-14.DOI: 10.1520/D6641_D6641M-16E01.2Boldface numbers in parentheses refer to the list of references at the end of thistest method.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serv
15、iceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance w
16、ith internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1E177 Practice for Use of the Terms Prec
17、ision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in Databases (With-drawn 2015)4E14
18、34 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases (Withdrawn2015)4E1471 Guide for Identification of Fibers, Fillers, and CoreMaterials in Computerized Material Property Databases(Withdrawn 2015)42.2 ASTM Adjunct:Combined Loading Compression (CLC) Test F
19、ix-ture, D 6641 D6641M53. Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and their composites. TerminologyD883 defines terms relating to plastics. Terminology E6 definesterms relating to mechanical testing. Terminology E456 andPractice E177 define terms rela
20、ting to statistics. In the event ofa conflict between terms, Terminology D3878 shall haveprecedence over the other Terminology standards.3.2 Symbols: Across-sectional area of specimen in gagesectionByface-to-face percent bending in specimenCVsample coefficient of variation, in percentEclaminate comp
21、ressive modulusFculaminate ultimate compressive strengthFcrEuler buckling stressGxzthrough-thickness shear modulus of laminatehspecimen thicknessImoment of inertia of specimen cross sectionlgspecimen gage lengthnnumber of specimensPload carried by test specimenPfload carried by test specimen at fail
22、uresas used in a lay-up code, denotes that the preceding plydescription for the laminate is repeated symmetrically aboutits midplanesn-1sample standard deviationwspecimen gage widthxsample mean (average)ximeasured or derived propertyindicated normal strain from strain transducerxlaminate axial strai
23、nylaminate in-plane transverse strain1,2strain 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 (ProcedureA) or tabbed (Procedure B) straight-sided composite specimenof
24、 rectangular cross section shown schematically in Fig. 3.Atypical specimen is 140 mm 5.5 in. long and 13 mm 0.5 in.wide, having an unsupported (gage) length of 13 mm 0.5 in.when installed in the fixture. A gage length greater or less than13 mm is acceptable, subject to specimen buckling consider-ati
25、ons (see 8.2). The 13-mm 0.5 in. gage length providessufficient space to install bonded strain gages when they arerequired. The fixture, which subjects the specimen to combinedend- and shear-loading, is itself loaded in compression betweenflat platens in a universal testing machine. Load-strain data
26、 arecollected until failure occurs (or until a specified strain level is4The last approved version of this historical standard is referenced onwww.astm.org.5A detailed drawing for the fabrication of the test fixture shown in Figs. 1 and2 is available from ASTM Headquarters. Order Adjunct No. ADJD664
27、1.FIG. 1 Photograph of a Typical Combined Loading Compression (CLC) Test FixtureD6641/D6641M 1612achieved if only compressive modulus or Poissons ratio, orboth, are to be determined, and not the complete stress-straincurve to failure).5. Significance and Use5.1 This test method is designed to produc
28、e compressiveproperty data for material specifications, research anddevelopment, quality assurance, and structural design andanalysis. When tabbed (Procedure B) specimens, typicallyunidirectional composites, are tested, the CLC test method(combined shear end loading) has similarities to Test Methods
29、D3410/D3410M (shear loading) and D695 (end loading).When testing lower strength materials such that untabbed CLCspecimens can be used (ProcedureA), the benefits of combinedloading become particularly prominent. It may not be possibleto successfully test untabbed specimens of these same materi-als us
30、ing either of the other two methods. When specificlaminates are tested (primarily of the 90/0nsfamily, althoughother laminates containing at least one 0 ply can be used), theCLC data are frequently used to “back out” 0 ply strength,using lamination theory to calculate a 0 unidirectional laminastreng
31、th (1, 2). Factors that influence the compressive responseinclude: type of material, methods of material preparation andlay-up, specimen stacking sequence, specimen preparation,specimen conditioning, environment of testing, speed oftesting, time at temperature, void content, and volume percentreinfo
32、rcement. Composite properties in the test direction thatmay 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 ratio in compression.6. Interferences6.1 Because of
33、partial end loading of the specimen in thistest method, it is important that the ends of the specimen bemachined flat, parallel to each other, and perpendicular to thelong axis of the coupon (see Fig. 3), just as for Test MethodD695. Improper preparation may result in premature endcrushing of the sp
34、ecimen during loading, excessive inducedbending, or buckling, potentially invalidating 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,Note: Using stand
35、ard M61 (14-28 UNF) screws, the bolt torque required to test most composite material specimens successfully is typically between 2.5 and 3.0 N-m20 and 25 in.-lb.FIG. 2 Dimensioned Sketch of a Typical Combined Loading Compression (CLC) Test FixtureD6641/D6641M 1613the specimen thickness must be incre
36、ased or the gage lengthreduced. A practical limit on reducing gage length is maintain-ing adequate space in which to attach strain gages, if required.A gage length of at least about 9 mm 0.35 in. is typicallyrequired for this purpose. Bending or buckling, or both, canusually only be detected by the
37、use of back-to-back straingages mounted on the faces of the specimen (3). Bending andbuckling are not visually obvious during the test, or from anexamination of the specimen failure mode.6.3 For a valid test, final failure of the specimen must occurwithin the gage section. Which failure modes are de
38、emedacceptable will be governed by the particular material,configuration, and application (see 12.1).6.4 Untabbed (Procedure A) specimens of continuous-fiber-reinforced laminates having more than 50 % axially oriented(0) plies may require higher than acceptable fixture clampingforces to prevent end
39、crushing. Excessive clamping forcesinduce at the ends of the gage section local stress concentra-tions that may produce erroneously low strength results (see11.2.7). In such cases, the specimen must be tabbed (ProcedureB).6.5 If the outermost plies of a laminate are oriented at 0,the local stress co
40、ncentrations at the ends of the specimen gagesection may lead to premature failure of these 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
41、the total number of plies (1).6.6 The compressive strength and stiffness properties ofunidirectional composites as well as all laminate configurationsmay be determined using this test method, subject to somelimitations (1). One limitation is that the fixture clampingforces induced by the applied bol
42、t torques required to success-fully fail the composite before specimen end crushing must notinduce 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 unidirect
43、ional composite is likely to be unsuc-cessful because of the excessive clamping forces required toprevent specimen end crushing, whereas a lower strengthunidirectional composite may be successfully tested usingacceptable clamping forces. The use of a tabbed specimen to(1) The specimen ends must be p
44、arallel to each other within 0.03 mm 0.001 in. and also perpendicular to the longitudinal axisof the specimen within 0.03 0.001 in., for both Procedures A and B.(2) Nominal specimen and tabbing thickness can be varied, but must be uniform. Thickness irregularities (for example,thickness taper or sur
45、face imperfections) shall not exceed 0.03 mm 0.001 in. across the specimen or tab width or 0.06 mm 0.002in. along the specimen grip length or tab length.(3) Tabs are typically square-ended and on the order of 1.6 mm 0.06 in. thick, but thickness can be varied as required, asdiscussed in 8.2.(4) The
46、faces of the specimen may be lapped slightly to remove any local surface imperfections and irregularities, thusproviding flatter surfaces for more uniform gripping by the fixture.FIG. 3 Typical Test Specimen ConfigurationD6641/D6641M 1614increase the bearing area at the specimen ends is then necesar
47、y(1, 5). An untabbed thickness-tapered specimen, althoughnonstandard, has also been used to successfully test high-strength unidirectional composites (5).6.7 In multidirectional laminates, edge effects can affect themeasured strength and modulus of the laminate.7. Apparatus and Supplies7.1 Micromete
48、rs 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.A caliper of suitable size can also be used on machined edgesor very smooth too
49、led 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 with 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 which can be operate
