1、Designation: D 7264/D 7264M 07Standard Test Method forFlexural Properties of Polymer Matrix Composite Materials1This standard is issued under the fixed designation D 7264/D 7264M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the
2、 year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon (e) 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
3、 Procedure 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 Met
4、hod D 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, provid
5、ed that 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 sta
6、ted 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.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It
7、is theresponsibility 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:2D 790 Test Methods for Flexural Properties of Unreinforcedand Reinforced Plastics
8、 and Electrical Insulating MaterialsD 2344/D 2344M Test Method for Short-Beam Strength ofPolymer Matrix Composite Materials and Their LaminatesD 3878 Terminology for Composite MaterialsD 5229/D 5229M Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Compos
9、ite MaterialsD 5687/D 5687M Guide for Preparation of Flat CompositePanels with Processing Guidelines for Specimen Prepara-tionD 6272 Test Method for Flexural Properties of Unrein-forced and Reinforced Plastics and Electrical InsulatingMaterials by Four-Point BendingD 6856 Guide for Testing Fabric-Re
10、inforced “Textile”Composite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE18 Test Methods for Rockwell Hardness and RockwellSuperficial Hardness of Metallic MaterialsE 122 Practice for Calculating Sample Size to Estimate,Wit
11、h a Specified Tolerable Error, the Average for aCharacteristic of a Lot or ProcessE 177 Practice 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 Dat
12、abasesE 1434 Guide for Recording Mechanical Test Data of Fiber-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 DefinitionsTermino
13、logy D 3878 defines the terms re-lating to high-modulus fibers and their composites. Terminol-ogy E6defines terms relating to mechanical testing. Termi-nology E 456 and Practice E 177 define terms relating tostatistics. In the event of a conflict between terms, TerminologyD 3878 shall have precedenc
14、e over the other documents.1This 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 April 1, 2007. Published April 2007. Originallyapproved in 2006. Last
15、 previous edition approved in 2006 as D 7264/D 7264M 06.2For 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.3Avai
16、lable from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2 Definitions of Terms Specific to This Standard:3.2.1 flexur
17、al strength, nthe maximum stress at the 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 = sam
18、ple coefficient of variation, in percentEfchord= 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= mea
19、sured or derived propertyx = sample meand = mid-span deflection of the specimene = strain at the outer surface at mid-span of the specimens = 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
20、constant rate as follows:4.1.1 Procedure AThe 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 s
21、upport point. The distancebetween the loading 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
22、thedeformation reaches some pre-determined 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 applicatio
23、n members. Consequently, the maxi-mum flexural 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 configura
24、tions is the presence ofresultant vertical 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.
25、The distance between the outersupport members 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 D 2344/D 2344M.5. Significance and Use5.1
26、 This test method determines the flexural properties(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
27、 for optimum use with continuous-fiber-reinforced 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 D 790 (a plastics-focused methodcovering three-point flexure
28、) and D 6272 (a plastics-focusedmethod covering four-point flexure).5.2 This test method is intended to interrogate long-beamstrength in contrast to the short-beam strength evaluated byTest Method D 2344/D 2344M.5.3 Flexural properties determined by these procedures canbe used for quality control an
29、d specification purposes, and mayfind design applications.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.
30、6. Interferences6.1 Flexural properties may vary depending on which sur-face of the specimen is in compression, as no laminate isperfectly symmetric (even when full symmetry is intended);such differences will shift the neutral axis and will be furtheraffected by even modest asymmetry in the laminate
31、. 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.FIG. 1 Procedure ALoading DiagramFIG. 2 Procedure BLoading DiagramD 7264
32、/D 7264M 0726.2 For multidirectional laminates with 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 th
33、e flexural properties in Section 13of this standard 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 de
34、crease with decreasing width.6.4 Loading noses may be fixed, rotatable or rolling. Typi-cally, for testing composites, fixed or rotatable loading nosesare used. The type of loading nose can affect results, sincenon-rolling paired supports on either the tension or compres-sion side of the specimen in
35、troduce slight longitudinal forcesand resisting moments on the beam, which superpose with theintended loading. The type of supports used is to be reported asdescribed in Section 14. The loading noses should alsouniformly contact the specimen across its width. Lack ofuniform contact can affect flexur
36、al properties by initiatingdamage by crushing and by 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 M
37、achineProperly calibrated, which can beoperated at a 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
38、 exceed 1 % of the measured force. The accuracyof the testing machine shall be verified in accordance withPractices E4.7.2 Loading Noses and SupportsThe loading noses andsupports shall have cylindrical contact surfaces of radius 3.00mm 0.125 in. as shown in Fig. 3, with a hardness of 60 to 62HRC, as
39、 specified in Test Methods E18, and shall have finelyFIG. 3 Example Loading Nose and Supports for Procedures A (top) and B (bottom)D 7264/D 7264M 073ground surfaces free of indentation and burrs with all sharpedges relieved. Loading noses and supports may be arranged ina fixed, rotatable or rolling
40、arrangement. Typically, withcomposites, rotatable or fixed arrangements 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 on
41、machined edges or very smooth tooled surfaces. A micrometeror caliper with flat anvil faces shall be used to measure thelength of the specimen. The accuracy of the instrument(s) shallbe suitable for reading to within 1 % or better of the specimendimensions. For typical section geometries, an instrum
42、ent 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 shall be measured by aproperly
43、 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 temperature/vapor-levelcontrolled envir
44、onmental 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 D 5229/D 5229M. Chamber conditions shall be monitored either on anautomated continuous basi
45、s 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 temperaturewithin 63C 65F and the req
46、uired vapor level to within65 % relative humidity.8. Test Specimens8.1 Specimen PreparationGuide D 5687/D 5687M pro-vides recommended specimen preparation practices and shouldbe followed when practical.8.2 Specimen Size is chosen such that the flexural propertiesare determined accurately from the te
47、sts. 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 4 mm 0.16 in., and the st
48、andard 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 ofthe specimen shall be at l
49、east two unit cells, as defined in GuideD 6856. 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 differentsupport span-to-thickn
