1、Designation: D 6641/D 6641M 09Standard Test Method forCompressive Properties of Polymer Matrix CompositeMaterials Using a Combined Loading Compression (CLC)Test Fixture1This standard is issued under the fixed designation D 6641/D 6641M; the number immediately following the designation indicates they
2、ear 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 strength
3、and 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. Onerequiremen
4、t 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 of 50 % 0 plies, or equivalent (see 6.4). Materials ofhigher or
5、thotropy, 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 D 3410/D 3410M is a pure shear-loading compressiontest method and Test Method D 695 is a pure end-loading test
6、method.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
7、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 thestandard.NOTE 1Additional procedures for determining the
8、 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 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
9、 safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 695 Test Method for Compressive Properties of RigidPlasticsD 883 Terminology Relating to PlasticsD 3410/D 3410M Test Method for Compressive Propertiesof P
10、olymer Matrix Composite Materials with UnsupportedGage Section by Shear LoadingD 3878 Terminology for Composite MaterialsD 5229/D 5229M Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite MaterialsD 5379/D 5379M Test Method for Shear Properties ofC
11、omposite Materials by the V-Notched Beam MethodD 5467/D 5467M Test Method for Compressive Propertiesof Unidirectional Polymer Matrix Composite MaterialsUsing a Sandwich BeamD 5687/D 5687M Guide for Preparation of Flat CompositePanels with Processing Guidelines for Specimen Prepara-tionE4 Practices f
12、or Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE 122 Practice for Calculating Sample Size to Estimate,With Specified Precision, the Average for a Characteristicof a Lot or ProcessE 132 Test Method for Poissons Ratio at Room Tempera-tureE 177 Practic
13、e for Use of the Terms Precision and Bias inASTM Test MethodsE 456 Terminology Relating to Quality and StatisticsE 1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in Databases1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials a
14、nd is the direct responsibility of Subcommittee D30.04 onLamina and Laminate Test Methods.Current edition approved April 15, 2009. Published May 2009. Originallyapproved in 2001. Last previous edition approved in 2001 as D 6641/D 6641M-0112Boldface numbers in parentheses refer to the list of referen
15、ces at the end of thistest method.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.1Copyright ASTM Internation
16、al, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.E 1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE 1471 Guide for Identification of Fibers, Fillers, and CoreMaterials in Computerized Material Property Database
17、s2.2 ASTM Adjunct:Combined Loading Compression (CLC) TestFixture, D 6641/D6641M43. 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 t
18、esting. TerminologyE 456 and Practice E 177 define terms 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 specim
19、enCVsample coefficient of variation, in percentEclaminate compressive modulusFculaminate ultimate compressive strengthFcrEuler buckling stressGxzthrough-thickness shear modulus of laminatehspecimen thicknessImoment of inertia of specimen cross sectionlgspecimen gage lengthnnumber of specimensPload c
20、arried 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-1sample standard deviationwspecimen gage widthxsample mean (average)ximeasured or derived propertyindic
21、ated 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 as that shown in Figs. 1 and 2,oranycomparable fixture, can be used to test the untabbed (Procedure
22、A) 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 unsupported (gage) length of 13 mm 0.5 in.when installed in the fixture. A gage length greater or less than
23、13 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, which subjects the specimen to combinedend- and shear-loading, is itself loaded in compression betwee
24、nflat 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 to be determined, and not the complete stress-straincurve to failure).5. Significance and Use5.1 T
25、his test method is designed to produce compressiveproperty data for material specifications, research and devel-opment, quality assurance, and structural design and analysis.When tabbed (Procedure B) specimens, typically unidirec-tional composites, are tested, the CLC test method (combinedshear end
26、loading) has similarities to Test Methods D 3410/D 3410M (shear loading) and D 695 (end loading). Whentesting lower strength materials such that untabbed CLC4A detailed drawing for the fabrication of the test fixture shown in Figs. 1 and2 is available from ASTM Headquarters. Order Adjunct No. ADJD66
27、41.FIG. 1 Photograph of a Typical Combined Loading Compression (CLC) Test FixtureD 6641/D 6641M 092specimens 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 using either of
28、 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 laminastrength (1, 2). Fa
29、ctors 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 of test-ing, time at temperature, void content, and volume percentreinforcement. Co
30、mposite 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 partial end
31、 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 MethodD 695. Improper preparation may result in premature endcrushing of the specimen dur
32、ing 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,the specimen thickness must
33、 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 typicallyrequired for this purpose. Bending or buckling, or both, canusually only be detecte
34、d by the use of back-to-back straingages mounted on the faces of the specimen (3). Bending andNote: Using standard M631(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
35、 a Typical Combined Loading Compression (CLC) Test FixtureD 6641/D 6641M 093buckling 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 deemedaccep
36、table will be governed by the particular material, con-figuration, 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 crushin
37、g. 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 concentra
38、tions 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 the tot
39、al 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 bolt torqu
40、es 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 unidirectional c
41、omposite 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 toincrease the bearing area at the speci
42、men 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 effects can affect themeasured strength and modulus of the laminate.7. Apparatus a
43、nd 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.A caliper of suitable size can also be used on machined
44、 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 also perpendicular to the longitudinal axis of the specimen within 0.03 0.001 in.,
45、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 in. across the specimen or tab width or 0.06 mm 0.002 in. along the specimen grip
46、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 remove any local surface imperfections and irregularities, thus providing flatter s
47、urfaces for more uniformgripping by the fixture.FIG. 3 Typical Test Specimen ConfigurationD 6641/D 6641M 094length, 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 ac
48、curacy 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 crosshead speed overthe specified range. The test machine mechanism shall beessent
49、ially 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 shall be capable of maintaining the requiredrelative temperature to within 63C
