1、Designation: D2344/D2344M 13Standard Test Method forShort-Beam Strength of Polymer Matrix Composite Materialsand Their Laminates1This standard is issued under the fixed designation D2344/D2344M; the number immediately following the designation indicates theyear of original adoption or, in the case o
2、f 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test met
3、hod determines the short-beam strength ofhigh-modulus fiber-reinforced composite materials. The speci-men is a short beam machined from a curved or a flat laminateup to 6.00 mm 0.25 in. thick. The beam is loaded inthree-point bending.1.2 Application of this test method is limited to continuous-or di
4、scontinuous-fiber-reinforced polymer matrix composites,for which the elastic properties are balanced and symmetricwith respect to the longitudinal axis of the beam.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system m
5、ay not be exact equivalents; therefore, eachsystem must be used independently of the other. Combiningvalues from the two systems may result in nonconformancewith the standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibi
6、lity 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:2D792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by Displacemen
7、tD883 Terminology Relating to PlasticsD2584 Test Method for Ignition Loss of Cured ReinforcedResinsD2734 Test Methods for Void Content of Reinforced PlasticsD3171 Test Methods for Constituent Content of CompositeMaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for MoistureA
8、bsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsD5687/D5687M Guide for Preparation of Flat CompositePanels with Processing Guidelines for Specimen Prepara-tionE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanica
9、l TestingE18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Characteristic of aLot or ProcessE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating
10、to Quality and StatisticsE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE1471 Guide for Identification of Fibers, Fillers, and CoreMaterials in Compute
11、rized Material Property Databases3. Terminology3.1 DefinitionsTerminology D3878 defines the terms re-lating to high-modulus fibers and their composites. Terminol-ogy D883 defines terms relating to plastics. Terminology E6defines terms relating to mechanical testing. Terminology E456and Practice E177
12、 define terms relating to statistics. In theevent of a conflict between definitions, Terminology D3878shall have precedence over the other documents.NOTE 1If the term represents a physical quantity, its analyticaldimensions are stated immediately following the term (or letter symbol) infundamental d
13、imension form, using the following ASTM standard sym-bology for fundamental dimensions, shown within square brackets: Mfor mass, L for length, T for time, for thermodynamic temperature,and nd for nondimensional quantities. Use of these symbols is restrictedto analytical dimensions when used with squ
14、are brackets, as the symbolsmay have other definitions when used without the brackets.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 Oct. 1, 20
15、13. Published December 2013. Originallyapproved in 1965. Last previous edition approved in 2006 as D2344 00R06. DOI:10.1520/D2344_D2344M-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volum
16、e information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 Definitions of Terms Specific to This Standard:3.2.1 balanced laminate, na continuous fiber-reinforcedl
17、aminate in which each + lamina, measured with respect to thelaminate reference axis, is balanced by a lamina of the samematerial (for example, 0/+45/45/+45/45/0).3.2.2 short-beam strength, nthe shear stress as calculatedin Eq 1, developed at the specimen mid-plane at the failureevent specified in 11
18、.6.3.2.2.1 DiscussionAlthough shear is the dominant appliedloading in this test method, the internal stresses are complexand a variety of failure modes can occur. Elasticity solutions byBergetal(1)3, Whitney (2), and Sullivan and Van Oene (3)have all demonstrated inadequacies in classical beam theor
19、y indefining the stress state in the short-beam configuration. Thesesolutions show that the parabolic shear-stress distribution aspredicted by Eq 1 only occurs, and then not exactly, on planesmidway between the loading nose and support points. Awayfrom these planes, the stress distributions become s
20、kewed, withpeak stresses occurring near the loading nose and supportpoints. Of particular significance is the stress state local to theloading nose in which the severe shear-stress concentrationcombined with transverse and in-plane compressive stresseshas been shown to initiate failure. However, for
21、 the moreductile matrices, plastic yielding may alleviate the situationunder the loading nose (1) and allow other failure modes tooccur such as bottom surface fiber tension (2). Consequently,unless mid-plane interlaminar failure has been clearlyobserved, the short-beam strength determined from this
22、testmethod cannot be attributed to a shear property, and the use ofEq 1 will not yield an accurate value for shear strength.3.2.3 symmetric laminate, na continuous fiber-reinforcedlaminate in which each ply above the mid-plane is identicallymatched (in terms of position, orientation, and mechanicalp
23、roperties) with one below the mid-plane.3.3 Symbols:bspecimen width.CVsample coefficient of variation (in percent).Fsbsshort-beam strength.hspecimen thickness.nnumber of specimens.Pmmaximum load observed during the test.ximeasured or derived property for an individual specimenfrom the sample populat
24、ion.xsample mean (average).4. Summary of Test Method4.1 The short-beam test specimens (Figs. 1-4) are center-loaded as shown in Figs. 5 and 6. The specimen ends rest ontwo supports that allow lateral motion, the load being appliedby means of a loading nose directly centered on the midpointof the tes
25、t specimen.5. Significance and Use5.1 In most cases, because of the complexity of internalstresses and the variety of failure modes that can occur in thisspecimen, it is not generally possible to relate the short-beamstrength to any one material property. However, failures arenormally dominated by r
26、esin and interlaminar properties, andthe test results have been found to be repeatable for a givenspecimen geometry, material system, and stacking sequence(4).5.2 Short-beam strength determined by this test method canbe used for quality control and process specification purposes.It can also be used
27、for comparative testing of compositematerials, provided that failures occur consistently in the samemode (5).5.3 This test method is not limited to specimens within therange specified in Section 8, but is limited to the use of aloading span length-to-specimen thickness ratio of 4.0 and aminimum spec
28、imen thickness of 2.0 mm 0.08 in.6. Interferences6.1 Accurate reporting of observed failure modes is essen-tial for meaningful data interpretation, in particular, the detec-tion of initial damage modes.7. Apparatus7.1 Testing Machine, properly calibrated, which can beoperated at a constant rate of c
29、rosshead motion, and which theerror in the loading system shall not exceed 61 %. Theload-indicating mechanism shall be essentially free of inertia3Boldface numbers in parentheses refer to the list of references at the end of thisstandard.NOTE 1Drawing interpretation perANSIY14.5-1982 andANSI/ASMB46.
30、1-1986.NOTE 2Ply orientation tolerance 60.5 relative to B.FIG. 1 Flat Specimen Configuration (SI)D2344/D2344M 132lag at the crosshead rate used. Inertia lag may not exceed 1 %of the measured load.The accuracy of the testing machine shallbe verified in accordance with Practices E4.7.2 Loading Nose an
31、d Supports, as shown in Figs. 5 and 6,shall be 6.00 6 0.50 mm 0.250 6 0.020 in. and 3.00 6 0.40mm 0.125 6 0.010 in. diameter cylinders, respectively, witha hardness of 60 to 62 HRC, as specified in Test Methods E18,and shall have finely ground surfaces free of indentation andburrs with all sharp edg
32、es relieved. The loading configurationshown in Fig. 5 is recommended for curved specimens with aradius r to specimen thickness h ratio of r/h of 5 or less. Theloading configuration shown in Fig. 6 is recommended for flatspecimens as well as curved specimens with a r/h ratio ofgreater than 5.7.3 Micr
33、ometersFor width and thickness measurements,the micrometers shall use a 4- to 5-mm (0.16- to 0.2-in.)nominal diameter ball interface on an irregular surface such asthe bag side of a laminate and a flat anvil interface on machinededges or very smooth tooled surfaces. A micrometer or caliperwith flat
34、anvil faces shall be used to measure the length of thespecimen. The accuracy of the instrument(s) shall be suitablefor reading to within 1 % of the sample dimensions. For typicalsection geometries, an instrument with an accuracy of 60.002mm (60.0001 in.) is desirable for thickness and widthmeasureme
35、nt, while an instrument with an accuracy of 60.1mm (60.004 in.) is adequate for length measurement.7.4 Conditioning Chamber, when conditioning materials atnonlaboratory environments, a temperature/vapor-level-controlled environmental conditioning chamber is required thatshall be capable of maintaini
36、ng the required temperature towithin 63C (65F) and the required vapor level to within63 %. Chamber conditions shall be monitored either on anautomated continuous basis or on a manual basis at regularintervals.7.5 Environmental Test Chamber, an environmental testchamber is required for test environme
37、nts other than ambienttesting laboratory conditions. This chamber shall be capable ofmaintaining the test specimen at the required test environmentduring the mechanical test method.8. Sampling and Test Specimens8.1 SamplingTest at least five specimens per test condi-tion unless valid results can be
38、gained through the use of fewerspecimens, as in the case of a designed experiment. Forstatistically significant data, consult the procedures outlined inPractice E122. Report the method of sampling.8.2 Geometry:8.2.1 Laminate ConfigurationsBoth multidirectional andpure unidirectional laminates can be
39、 tested, provided that thereare at least 10 % 0 fibers in the span direction of the beam(preferably well distributed through the thickness), and that thelaminates are both balanced and symmetric with respect to thespan direction of the beam.8.2.2 Specimen ConfigurationsTypical configurations forthe
40、flat and curved specimens are shown in Figs. 1-4. Forspecimen thicknesses other than those shown, the followinggeometries are recommended:Specimen length = thickness 6Specimen width, b = thickness 2.0NOTE 2A discussion of width-to-thickness effects is available inAdams and Lewis (6).8.2.2.1 For curv
41、ed beam specimens, it is recommended thatthe arc should not exceed 30. Also, for these specimens, thespecimen length is defined as the minimum chord length.8.3 Specimen PreparationGuide D5687/D5687M pro-vides recommended specimen preparation practices and shouldbe followed where practical.8.3.1 Lami
42、nate FabricationLaminates may be hand-laid,filament-wound or tow-placed, and molded by any suitablelaminating means, such as press, bag, autoclave, or resintransfer molding.8.3.2 Machining MethodsSpecimen preparation is impor-tant for these specimens. Take precautions when cuttingspecimens from the
43、rings or plates to avoid notches, undercuts,rough or uneven surfaces, or delaminations as a result ofinappropriate machining methods. Obtain final dimensions bywater-lubricated precision sawing, milling, or grinding. Theuse of diamond tooling has been found to be extremelyeffective for many material
44、 systems. Edges should be flat andparallel within the specified tolerances.8.3.3 LabelingLabel the specimens so that they will bedistinct from each other and traceable back to the raw material,NOTE 1Drawing interpretation per ANSI Y14.5-1982 and ANSI/ASME B46.1-1986.NOTE 2Ply orientation tolerance 6
45、0.5 relative to B.FIG. 2 Flat Specimen Configuration (Inch Pound)D2344/D2344M 133in a manner that will both be unaffected by the test method andnot influence the test method.9. Calibration9.1 The accuracy of all measuring equipment shall havecertified calibrations that are current at the time of use
46、 of theequipment.10. Conditioning10.1 Standard Conditioning ProcedureUnless a differentenvironment is specified as part of the test method, conditionthe test specimens in accordance with Procedure C of TestMethod D5229/D5229M, and store and test at standard labo-ratory atmosphere (23 6 3C (73 6 5F)
47、and 50 6 10 %relative humidity).11. Procedure11.1 Parameters to Be Specified Before Test:11.1.1 The specimen sampling method and coupon geom-etry.11.1.2 The material properties and data-reporting formatdesired.NOTE 3Determine specific material property, accuracy, and data-reporting requirements befo
48、re test for proper selection of instrumentationand data-recording equipment. Estimate operating stress levels to aid incalibration of equipment and determination of equipment settings.11.1.3 The environmental conditioning test parameters.11.1.4 If performed, the sampling test method, coupongeometry,
49、 and test parameters used to determine density andreinforcement volume.NOTE 1Drawing interpretation per ANSI Y14.5-1982 and ANSI/ASM B46.1-1986.NOTE 2Ply orientation tolerance 60.5 relative to A.FIG. 3 Curved Specimen Configuration (SI)D2344/D2344M 13411.1.5 Optional nominal specimen thickness to be used toset the support span dimension.11.2 General Instructions:11.2.1 Report any deviations from this test method, whetherintentional or inadvertent.11.2.2 If specific gravity, density, reinforcement vo
