1、Designation: D6641/D6641M 14Standard 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.1. Scope1.1 This test method determines the compressive strengthand
3、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(Procedure A) or tabbed (Procedure B), as required. Onerequirement fo
4、r 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 of 50 % 0 plies, or equivalent (see 6.4). Materials ofhigher orthot
5、ropy, 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 compressiontest method and Test Method D695 is a pure end-loading testmethod.
6、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 unitsare to be regarded separately as standard. Within the test th
7、einch-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 thestandard.NOTE 1Additional procedures for determining the compre
8、ssive 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 theresponsibility of the user of this standard to establish appro-priate saf
9、ety 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 PlasticsD3410/D3410M Test Method for Compressive Properties ofPolymer M
10、atrix 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 MaterialsD5379/D5379M Test Method for Shear Properties of Com-posite Mat
11、erials 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 Processing Guidelines for Specimen Prepara-tionE4 Practices for Force Verif
12、ication 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 Poissons Ratio at Room TemperatureE177 Practice for Use of the Te
13、rms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study to1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.04 onLamin
14、a and Laminate Test Methods.Current edition approved Aug. 1, 2014. Published November 2014. Originallyapproved in 2001. Last previous edition approved in 2009 as D6641/D6641M-09.DOI: 10.1520/D6641_D6641M-14.2Boldface numbers in parentheses refer to the list of references at the end of thistest metho
15、d.3For 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box
16、 C700, West Conshohocken, PA 19428-2959. United States1Determine the Precision of a Test MethodE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE1471 Gui
17、de for Identification of Fibers, Fillers, and CoreMaterials in Computerized Material Property Databases2.2 ASTM Adjunct:Combined Loading Compression (CLC) Test Fix-ture, D 6641 D6641M43. Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and their composites. Te
18、rminologyD883 defines terms relating to plastics. Terminology E6 definesterms relating to mechanical testing. Terminology E456 andPractice E177 define terms relating to statistics. In the event ofa conflict between terms, Terminology D3878 shall haveprecedence over the other Terminology standards.3.
19、2 Symbols: Across-sectional area of specimen in gagesectionByface-to-face percent bending in specimenCVsample coefficient of variation, in percentEclaminate compressive modulusFculaminate ultimate compressive strengthFcrEuler buckling stressGxzthrough-thickness shear modulus of laminatehspecimen thi
20、cknessImoment 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 midplanesn-1sam
21、ple standard deviationwspecimen gage widthxsample mean (average)ximeasured or derived propertyindicated normal strain from strain transducerxlaminate axial strainylaminate in-plane transverse strain1,2strain gage readingsvxyccompressive Poissons ratio4. Summary of Test Method4.1 A test fixture such
22、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 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 unsuppor
23、ted (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-ations (see 8.2). The 13-mm 0.5 in. gage length providessufficient space to install bonded strain gages when they arerequired. The fixture, wh
24、ich subjects the specimen to combinedend- and shear-loading, is itself loaded in compression betweenflat platens in a universal testing machine. Load-strain data arecollected until failure occurs (or until a specified strain level isachieved if only compressive modulus or Poissons ratio, orboth, are
25、 to be determined, and not the complete stress-straincurve to failure).5. Significance and Use5.1 This test method is designed to produce compressiveproperty data for material specifications, research anddevelopment, quality assurance, and structural design andanalysis. When tabbed (Procedure B) spe
26、cimens, typically4A detailed drawing for the fabrication of the test fixture shown in Figs. 1 and2 is available from ASTM Headquarters. Order Adjunct No. ADJD6641.FIG. 1 Photograph of a Typical Combined Loading Compression (CLC) Test FixtureD6641/D6641M 142unidirectional composites, are tested, the
27、CLC test method(combined shear end loading) has similarities to Test MethodsD3410/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
28、 possibleto successfully test untabbed specimens of these same materi-als using 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 s
29、trength,using lamination theory to calculate a 0 unidirectional laminastrength (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,
30、speed oftesting, time at temperature, void content, and volume percentreinforcement. 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 elast
31、icity,and5.1.4 Poissons ratio 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 flat, parallel to each other, and perpendicular to thelong axis of the coupon (see Fig. 3), just as for Test Me
32、thodD695. Improper preparation may result in premature endcrushing of the specimen 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 th
33、in in relation to the gage length (see 8.2). In such cases,the specimen thickness must be increased 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 typica
34、llyrequired for this purpose. Bending or buckling, or both, canusually only be detected by the 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.Note: Using standa
35、rd 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 1436.3 For a valid test, final failure of
36、 the specimen must occurwithin the gage section. Which failure modes are deemedacceptable 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) plie
37、s may require higher than acceptable fixture clampingforces to prevent end 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
38、 If the outermost plies of a laminate are oriented at 0,the local stress concentrations 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 lownumbe
39、rs 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 ofunidirectional composites as well as all laminate configurationsmay be determined using this test method, subject to somelimitations (1). O
40、ne limitation is that the fixture clampingforces induced by the applied bolt 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 co
41、mpressive strength. For example, testing an untabbedhigh-strength unidirectional 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 clam
42、ping forces. The use of a tabbed specimen toincrease the bearing area at the specimen ends is then necesary(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
43、effects can affect themeasured strength and modulus of the laminate.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 tool
44、ed surfaces, shall be used.A 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 sampleNotes:(1) The specimen ends must be parallel to each other within 0.03 mm 0.001 in. and
45、also perpendicular to the longitudinal axis of 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 surface imperfections) shallnot exceed 0.03 mm 0.001
46、in. across the specimen or tab width or 0.06 mm 0.002 in. 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, as discussed in 8.2.(4) The faces of the specimen may be lapped slightly to r
47、emove any local surface imperfections and irregularities, thus providing flatter surfaces for more uniformgripping by the fixture.FIG. 3 Typical Test Specimen ConfigurationD6641/D6641M 144length, width and thickness. For typical specimen geometries,an instrument with an accuracy of 62.5 m 60.0001 in
48、. 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 operated at constant cr
49、osshead 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 appropriateforce-measuring device (for example, a load cell). The accu-racy of the test machine shall be in accordance with PracticesE4.7.4 Conditioning ChamberWhen conditioning materialsin other than ambient laboratory environments, a temperature-/moisture-level controlled environmental conditioning chamberis required that
