1、Designation: D7264/D7264M 15Standard Test Method forFlexural Properties of Polymer Matrix Composite Materials1This standard is issued under the fixed designation D7264/D7264M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the yea
2、r 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 flexural stiffness andstrength properties of polymer matrix composites.1.1.1 Proc
3、edure AA three-point loading system utilizingcenter loading on a simply supported beam.1.1.2 Procedure BA four-point loading system utilizingtwo load points equally spaced from their adjacent supportpoints, with a distance between load points of one-half of thesupport span.NOTE 1Unlike Test Method D
4、6272, which allows loading at bothone-third and one-half of the support span, in order to standardizegeometry and simplify calculations this standard permits loading at onlyone-half the support span.1.2 For comparison purposes, tests may be conducted ac-cording to either test procedure, provided tha
5、t the sameprocedure is used for all tests, since the two proceduresgenerally give slightly different property values.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. Within the text, theinch-pound units are shown in brackets. The values stated in
6、each 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.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is the
7、responsibility 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:2D790 Test Methods for Flexural Properties of Unreinforcedand Reinforced Plastics and El
8、ectrical Insulating Materi-alsD2344/D2344M Test Method for Short-Beam Strength ofPolymer Matrix Composite Materials and Their LaminatesD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite Material
9、sD5687/D5687M Guide for Preparation of Flat CompositePanels with Processing Guidelines for Specimen Prepara-tionD6272 Test Method for Flexural Properties of Unreinforcedand Reinforced Plastics and Electrical Insulating Materi-als by Four-Point BendingD6856 Guide for Testing Fabric-Reinforced “Textil
10、e” Com-posite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Charact
11、eristic of aLot or ProcessE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE1434 Guide for Recording Mechanical Test Data of Fib
12、er-Reinforced Composite Materials in Databases2.2 Other Documents:ANSI Y14.5-1999 Dimensioning and TolerancingIncludes Inch and Metric3ANSI B46.1-1995 Surface Texture (Surface Roughness,Waviness and Lay)33. Terminology3.1 DefinitionsTerminology D3878 defines the terms re-lating to high-modulus fiber
13、s and their composites. Terminol-ogy E6 defines terms relating to mechanical testing. Terminol-ogy E456 and Practice E177 define terms relating to statistics.1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.0
14、4 onLamina and Laminate Test Methods.Current edition approved April 1, 2015. Published May 2015. Originallyapproved in 2006. Last previous edition approved in 2007 as D7264/D7264M 07.DOI: 10.1520/D7264_D7264M-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cus
15、tomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM Interna
16、tional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1In the event of a conflict between terms, Terminology D3878shall have precedence over the other documents.3.2 Definitions of Terms Specific to This Standard:3.2.1 flexural strength, nthe maximum stress at the
17、 outersurface of a flexure test specimen corresponding to the peakapplied force prior to flexural failure.3.2.2 flexural modulus, nthe ratio of stress range tocorresponding strain range for a test specimen loaded inflexure.3.3 Symbols:b = specimen widthCV = sample coefficient of variation, in percen
18、tEfchord= flexural chord modulus of elasticityEfsecant= flexural secant modulus of elasticityh = specimen thicknessL = support spanm = slope of the secant of the load-deflection curven = number of specimensP = applied forcesn-1= sample standard deviationxi= measured or derived propertyx5 sample mean
19、 = mid-span deflection of the specimen = strain at the outer surface at mid-span of the specimen = stress at the outer surface at mid-span of the specimen4. Summary of Test Method4.1 A bar of rectangular cross section, supported as a beam,is deflected at a constant rate as follows:4.1.1 Procedure AT
20、he bar rests on two supports and isloaded by means of a loading nose midway between thesupports (see Fig. 1).4.1.2 Procedure BThe bar rests on two supports and isloaded at two points (by means of two loading noses), each anequal distance from the adjacent support point. The distancebetween the loadi
21、ng noses (that is, the load span) is one-half ofthe support span (see Fig. 2).4.2 Force applied to the specimen and resulting specimendeflection at the center of span are measured and recorded untilthe failure occurs on either one of the outer surfaces, or thedeformation reaches some pre-determined
22、value.4.3 The major difference between four-point and three-pointloading configurations is the location of maximum bendingmoment and maximum flexural stress. With the four-pointconfiguration the bending moment is constant between thecentral force application members. Consequently, the maxi-mum flexu
23、ral stress is uniform between the central forceapplication members. In the three-point configuration, themaximum flexural stress is located directly under the centerforce application member. Another difference between thethree-point and four-point configurations is the presence ofresultant vertical
24、shear force in the three-point configurationeverywhere in the beam except right under the mid-point forceapplication member whereas in the four-point configuration,the area between the central force application members has noresultant vertical shear force. The distance between the outersupport membe
25、rs is the same as in the equivalent three-pointconfiguration.4.4 The test geometry is chosen to limit out-of-plane sheardeformations and avoid the type of short beam failure modesthat are interrogated in Test Method D2344/D2344M.5. Significance and Use5.1 This test method determines the flexural pro
26、perties(including strength, stiffness, and load/deflection behavior) ofpolymer matrix composite materials under the conditionsdefined. Procedure A is used for three-point loading andProcedure B is used for four-point loading. This test methodwas developed for optimum use with continuous-fiber-reinfo
27、rced polymer matrix composites and differs in severalrespects from other flexure methods, including the use of astandard span-to-thickness ratio of 32:1 versus the 16:1 ratioused by Test Methods D790 (a plastics-focused method cov-ering three-point flexure) and D6272 (a plastics-focusedmethod coveri
28、ng four-point flexure).5.2 This test method is intended to interrogate long-beamstrength in contrast to the short-beam strength evaluated byTest Method D2344/D2344M.5.3 Flexural properties determined by these procedures canbe used for quality control and specification purposes, and mayfind design ap
29、plications.5.4 These procedures can be useful in the evaluation ofmultiple environmental conditions to determine which aredesign drivers and may require further testing.5.5 These procedures may also be used to determine flexuralproperties of structures.6. Interferences6.1 Flexural properties may var
30、y depending on which sur-face of the specimen is in compression, as no laminate isperfectly symmetric (even when full symmetry is intended);FIG. 1 Procedure ALoading DiagramFIG. 2 Procedure BLoading DiagramD7264/D7264M 152such differences will shift the neutral axis and will be furtheraffected by ev
31、en modest asymmetry in the laminate. Flexuralproperties may also vary with specimen thickness, condition-ing and/or testing environments, and rate of straining. Whenevaluating several datasets these parameters should be equiva-lent for all data in the comparison.6.2 For multidirectional laminates wi
32、th a small or moderatenumber of laminae, flexural modulus and flexural strength maybe affected by the ply-stacking sequence and will not neces-sarily correlate with extensional modulus, which is notstacking-sequence dependent.6.3 The calculation of the flexural properties in Section 13of this standa
33、rd is based on beam theory, while the specimensin general may be described as plates. The differences may insome cases be significant, particularly for laminates containinga large number of plies in the 645 direction. The deviationsfrom beam theory decrease with decreasing width.6.4 Loading noses ma
34、y be fixed, rotatable or rolling.Typically, for testing composites, fixed or rotatable loadingnoses are used. The type of loading nose can affect results,since non-rolling paired supports on either the tension orcompression side of the specimen introduce slight longitudinalforces and resisting momen
35、ts on the beam, which superposewith the intended loading. The type of supports used is to bereported as described in Section 14. The loading noses shouldalso uniformly contact the specimen across its width. Lack ofuniform contact can affect flexural properties by initiatingdamage by crushing and by
36、non-uniformly loading the beam.Formulas used in this standard assume a uniform line loadingat the specimen supports across the entire specimen width;deviations from this type of loading is beyond the scope of thisstandard.7. Apparatus7.1 Testing MachineProperly calibrated, which can beoperated at a
37、constant rate of crosshead motion, and in whichthe error in the force application system shall not exceed 61%of the full scale. The force indicating mechanism shall beessentially free of inertia lag at the crosshead rate used. Inertialag shall not exceed 1 % of the measured force. The accuracyof the
38、 testing machine shall be verified in accordance withPractices E4.7.2 Loading Noses and SupportsThe loading noses andsupports shall have cylindrical contact surfaces with a hardness55 HRC and shall have finely ground surfaces free ofindentation and burrs, with all sharp edges relieved. The radiiof t
39、he loading nose and supports shall be 5.0 6 1.0 mm 0.1976 0.004 in., as shown in Fig. 3, unless otherwise specified oragreed upon between the interested parties. Loading noses andsupports may be arranged in a fixed, rotatable or rollingarrangement. Typically, with composites, rotatable or fixedarran
40、gements are used.7.3 MicrometersFor width and thickness measurementsthe micrometers shall usea4to7mm0.16 to 0.28 in.nominal diameter ball-interface on an irregular surface such asthe bag side of a laminate, and a flat anvil interface onmachined edges or very smooth tooled surfaces. A micrometeror ca
41、liper with flat anvil faces shall be used to measure theFIG. 3 Example Loading Nose and Supports for Procedures A (top) and B (bottom)D7264/D7264M 153length of the specimen. The accuracy of the instrument(s) shallbe suitable for reading to within 1 % or better of the specimendimensions. For typical
42、section geometries, an instrument withan accuracy of 60.02 mm 60.001 in. is desirable forthickness and width measurement, while an instrument with anaccuracy of 60.1 mm 60.004 in. is adequate for lengthmeasurement.7.4 Deflection MeasurementSpecimen deflection at thecommon center of the loading span
43、shall be measured by aproperly calibrated device having an accuracy of 61% orbetter of the expected maximum displacement. The deviceshall automatically and continuously record the deflectionduring the test.7.5 Conditioning ChamberWhen conditioning materialsat non-laboratory environments, a temperatu
44、re/vapor-levelcontrolled environmental conditioning chamber is required thatshall be capable of maintaining the required temperature towithin 61C 62F and the required vapor level to within63 % relative humidity, as outlined in Test Method D5229/D5229M. Chamber conditions shall be monitored either on
45、 anautomated continuous basis or on a manual basis at regularintervals.7.6 Environmental Test ChamberAn environmental testchamber is required for test environments other than ambienttesting laboratory conditions. This chamber shall be capable ofmaintaining the test specimen at the required temperatu
46、rewithin 63C 65F and the required vapor level to within65 % relative humidity.8. Test Specimens8.1 Specimen PreparationGuide D5687/D5687M pro-vides recommended specimen preparation practices and shouldbe followed when practical.8.2 Specimen Size is chosen such that the flexural propertiesare determi
47、ned accurately from the tests. For flexural strength,the standard support span-to-thickness ratio is chosen such thatfailure occurs at the outer surface of the specimens, due only tothe bending moment (see Notes 2 and 3). The standardspan-to-thickness ratio is 32:1, the standard specimen thicknessis
48、 4 mm 0.16 in., and the standard specimen width is 13 mm0.5 in. with the specimen length being about 20 % longerthan the support span. See Figs. 4 and 5 for a drawing of thestandard test specimen in SI and inch-pound units, respectively.For fabric-reinforced textile composite materials, the width of
49、the specimen shall be at least two unit cells, as defined in GuideD6856. If the standard specimen thickness cannot be obtainedin a given material system, an alternate specimen thicknessshall be used while maintaining the support span-to-thicknessratio 32:1 and specimen width. Optional support span-to-thickness ratios of 16:1, 20:1, 40:1, and 60:1 may also be usedprovided it is so noted in the report. Also, the data obtainedfrom a test using one support span-to-thickness ratio may notbe compared with the data from another test using a
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