1、Designation: D6641/D6641M 14D6641/D6641M 16Standard 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 ind
2、icates 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method determines the compressi
3、ve strength and stiffness properties of polymer matrix composite materials usinga combined loading compression (CLC) (1)2 test fixture. This test method is applicable to general composites that are balancedand symmetric. The specimen may be untabbed (Procedure A) or tabbed (Procedure B), as required
4、. One requirement for asuccessful test is that the specimen ends do not crush during the test. Untabbed specimens are usually suitable for use withmaterials of low orthotropy, for example, fabrics, chopped fiber composites, and laminates with a maximum of 50 % 0 plies, orequivalent (see 6.4). Materi
5、als of higher orthotropy, including unidirectional composites, typically require tabs.1.2 The compressive force is introduced into the specimen by combined end- and shear-loading. In comparison, Test MethodD3410/D3410M is a pure shear-loading compression test method and Test Method D695 is a pure en
6、d-loading test method.1.3 Unidirectional (0 ply orientation) composites as well as multi-directional composite laminates, fabric composites, choppedfiber composites, and similar materials can be tested.1.4 The values stated in either SI units or inch-pound units are to be regarded separately as stan
7、dard. Within the test theinch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system mustbe used independently of the other. Combining values from the two systems may result in nonconformance with the standard.NOTE 1Additional procedures
8、 for determining the compressive properties 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 the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to
9、 establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D695 Test Method for Compressive Properties of Rigid PlasticsD883 Terminology Relating to PlasticsD3410/D3410M Test Method for Compressi
10、ve Properties of Polymer Matrix Composite Materials with Unsupported GageSection by Shear LoadingD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix CompositeMaterialsD5379/D5379M Test Method for Shear Pr
11、operties of Composite Materials by the V-Notched Beam MethodD5467/D5467M Test Method for Compressive Properties of Unidirectional Polymer Matrix Composite Materials Using aSandwich BeamD5687/D5687M Guide for Preparation of Flat Composite Panels with Processing Guidelines for Specimen Preparation1 Th
12、is test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.04 on Lamina andLaminate Test Methods.Current edition approved Aug. 1, 2014Nov. 1, 2016. Published November 2014November 2016. Originally approved in 2001. Last
13、previous edition approved in 20092014as D6641/D6641M-09.-14. DOI: 10.1520/D6641_D6641M-14.10.1520/D6641_D6641M-16.2 Boldface numbers in parentheses refer to the list of references at the end of this test method.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Custo
14、mer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the
15、 previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright AS
16、TM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Av
17、erage for a Characteristic of a Lot orProcessE132 Test Method for Poissons Ratio at Room TemperatureE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study to Determine the Prec
18、ision of a Test MethodE1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in Databases (Withdrawn 2015)4E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases (Withdrawn 2015)4E1471 Guide for Identification of Fibers, Fil
19、lers, and Core Materials in Computerized Material Property Databases (Withdrawn2015)42.2 ASTM Adjunct:Combined Loading Compression (CLC) Test Fixture, D 6641D6641M53. Terminology3.1 DefinitionsTerminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology D883defin
20、es terms relating to plastics. Terminology E6 defines terms relating to mechanical testing. Terminology E456 and PracticeE177 define terms relating to statistics. In the event of a conflict between terms, Terminology D3878 shall have precedence overthe other Terminology standards.3.2 Symbols: Across
21、-sectional area of specimen in gage sectionByface-to-face percent bending in specimenCVsample coefficient of variation, in percentEclaminate compressive modulusFculaminate ultimate compressive strengthFcrEuler buckling stressGxzthrough-thickness shear modulus of laminatehspecimen thicknessImoment of
22、 inertia of specimen cross sectionlgspecimen gage lengthnnumber of specimensPload carried by test specimenPfload carried by test specimen at failure4 The last approved version of this historical standard is referenced on www.astm.org.5 A detailed drawing for the fabrication of the test fixture shown
23、 in Figs. 1 and 2 is available from ASTM Headquarters. Order Adjunct No. ADJD6641.FIG. 1 Photograph of a Typical Combined Loading Compression (CLC) Test FixtureD6641/D6641M 162sas used in a lay-up code, denotes that the preceding plydescription for the laminate is repeated symmetrically aboutits mid
24、planesn-1sample 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 f
25、ixture such as that shown in Figs. 1 and 2, or any comparable fixture, can be used to test the untabbed (ProcedureA) or tabbed (Procedure B) straight-sided composite specimen of rectangular cross section shown schematically in Fig. 3.Atypicalspecimen is 140 mm 5.5 in. long and 13 mm 0.5 in. wide, ha
26、ving an unsupported (gage) length of 13 mm 0.5 in. when installedin the fixture. A gage length greater or less than 13 mm is acceptable, subject to specimen buckling considerations (see 8.2). The13-mm 0.5 in. gage length provides sufficient space to install bonded strain gages when they are required
27、. The fixture, whichsubjects the specimen to combined end- and shear-loading, is itself loaded in compression between flat platens in a universal testingmachine. Load-strain data are collected until failure occurs (or until a specified strain level is achieved if only compressive modulusor Poissons
28、ratio, or both, are to be determined, and not the complete stress-strain curve to failure).Note: Using standard 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
29、Typical Combined Loading Compression (CLC) Test FixtureD6641/D6641M 1635. Significance and Use5.1 This test method is designed to produce compressive property data for material specifications, research and development,quality assurance, and structural design and analysis. When tabbed (Procedure B) s
30、pecimens, typically unidirectional composites,are tested, the CLC test method (combined shear end loading) has similarities to Test Methods D3410/D3410M (shear loading)and D695 (end loading). When testing lower strength materials such that untabbed CLC specimens can be used (ProcedureA), thebenefits
31、 of combined loading become particularly prominent. It may not be possible to successfully test untabbed specimens ofthese same materials using either of the other two methods. When specific laminates are tested (primarily of the 90/0ns family,although other laminates containing at least one 0 ply c
32、an be used), the CLC data are frequently used to “back out” 0 ply strength,using lamination theory to calculate a 0 unidirectional lamina strength (1, 2). Factors that influence the compressive responseinclude: type of material, methods of material preparation and lay-up, specimen stacking sequence,
33、 specimen preparation,specimen conditioning, environment of testing, speed of testing, time at temperature, void content, and volume percentreinforcement. Composite properties in the test direction that may be obtained from this test method include:5.1.1 Ultimate compressive strength,5.1.2 Ultimate
34、compressive strain,5.1.3 Compressive (linear or chord) modulus of elasticity, and5.1.4 Poissons ratio in compression.Notes:(1) The specimen ends must be parallel 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 Proc
35、edures 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) 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
36、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 faces of the specimen may be lapped slightly to remove any local surface imperfections and irregularities, thusproviding flatter surfaces for more
37、 uniform gripping by the fixture.(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.,for both Procedures A and B.(2) Nominal specimen and tabbing thickness can be varied, but must be unifo
38、rm. 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 length or tab length.(3) Tabs are typically square-ended and on the order of 1.6 mm 0.06 in. thick, but
39、 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 surfaces for more uniformgripping by the fixture.FIG. 3 Typical Test Specimen ConfigurationD6641/D6641M
40、1646. Interferences6.1 Because of partial end loading of the specimen in this test method, it is important that the ends of the specimen be machinedflat, parallel to each other, and perpendicular to the long axis of the coupon (see Fig. 3), just as for Test Method D695. Improperpreparation may resul
41、t in premature end crushing of the specimen during loading, excessive induced bending, or buckling,potentially invalidating the test.6.2 Erroneously low laminate compressive strengths will be produced as a result of Euler column buckling if the specimen istoo thin in relation to the gage length (see
42、 8.2). In such cases, the specimen thickness must be increased or the gage length reduced.A practical limit on reducing gage length is maintaining adequate space in which to attach strain gages, if required. A gage lengthof at least about 9 mm 0.35 in. is typically required for this purpose. Bending
43、 or buckling, or both, can usually only be detectedby the use of back-to-back strain gages mounted on the faces of the specimen (3). Bending and buckling are not visually obviousduring the test, or from an examination of the specimen failure mode.6.3 For a valid test, final failure of the specimen m
44、ust occur within the gage section.Which failure modes are deemed acceptablewill 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
45、higher than acceptable fixture clamping forces to prevent end crushing. Excessive clamping forces induce at theends of the gage section local stress concentrations that may produce erroneously low strength results (see 11.2.7). In such cases,the specimen must be tabbed (Procedure B).6.5 If the outer
46、most plies of a laminate are oriented at 0, the local stress concentrations at the ends of the specimen gage sectionmay lead to premature failure of these primary load-bearing plies, producing erroneously low laminate strength results. This isparticularly true for specimens with low numbers of plies
47、, since then the outer plies represent a significant fraction of the totalnumber of plies (1).6.6 The compressive strength and stiffness properties of unidirectional composites as well as all laminate configurations maybe determined using this test method, subject to some limitations (1). One limita
48、tion is that the fixture clamping forces inducedby the applied bolt torques required to successfully fail the composite before specimen end crushing must not induce significantstress concentrations at the ends of the gage section (4). Such stress concentrations will degrade the measured compressives
49、trength. For example, testing an untabbed high-strength unidirectional composite is likely to be unsuccessful because of theexcessive clamping forces required to prevent specimen end crushing, whereas a lower strength unidirectional composite may besuccessfully tested using acceptable clamping forces. The use of a tabbed specimen to increase the bearing area at the specimenends is then necesary (1, 5). An untabbed thickness-tapered specimen, although nonstandard, has also been used to successfullytes
