1、Designation: D2344/D2344M 13D2344/D2344M 16Standard 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
2、, 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.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Sc
3、ope1.1 This test method determines the short-beam strength of high-modulus fiber-reinforced composite materials. The specimenis a short beam machined from a curved or a flat laminate up to 6.00 mm 0.25 in. thick. The beam is loaded in three-pointbending.1.2 Application of this test method is limited
4、 to continuous- or discontinuous-fiber-reinforced polymer matrix composites, forwhich the elastic properties are balanced and symmetric with respect to the longitudinal axis of the beam.1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values
5、 stated in eachsystem may not be exact equivalents; therefore, each system must be used independently of the other. Combining values from thetwo systems may result in nonconformance with the standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with it
6、s use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D792 Test Methods for Density and Specific Gravity (Relative Density) of P
7、lastics by DisplacementD883 Terminology Relating to PlasticsD2584 Test Method for Ignition Loss of Cured Reinforced ResinsD2734 Test Methods for Void Content of Reinforced PlasticsD3171 Test Methods for Constituent Content of Composite MaterialsD3878 Terminology for Composite MaterialsD5229/D5229M T
8、est Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix CompositeMaterialsD5687/D5687M Guide for Preparation of Flat Composite Panels with Processing Guidelines for Specimen PreparationE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating
9、 to Methods of Mechanical TestingE18 Test Methods for Rockwell Hardness of Metallic MaterialsE122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot orProcessE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE
10、456 Terminology Relating to Quality and StatisticsE1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in Databases (Withdrawn 2015)3E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases (Withdrawn 2015)31 This test metho
11、d 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 Oct. 1, 2013July 1, 2016. Published December 2013July 2016. Originally approved in 1965. Last previous edition
12、approved in 20062013 asD2344 00D2344 13.R06. DOI: 10.1520/D2344_D2344M-13.10.1520/D2344_D2344M-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Docum
13、ent Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.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 previous version. Becausei
14、t 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 ASTM International, 100 Barr
15、Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E1471 Guide for Identification of Fibers, Fillers, and Core Materials in Computerized Material Property Databases (Withdrawn2015)33. Terminology3.1 DefinitionsTerminology D3878 defines the terms relating to high-modulus fiber
16、s and their composites. Terminology D883defines 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 definitions, Terminology D3878 shall have precedenceover
17、the other documents.NOTE 1If the term represents a physical quantity, its analytical dimensions are stated immediately following the term (or letter symbol) infundamental dimension form, using the following ASTM standard symbology for fundamental dimensions, shown within square brackets: M for mass,
18、L for length, T for time, for thermodynamic temperature, and nd for nondimensional quantities. Use of these symbols is restricted to analyticaldimensions when used with square brackets, as the symbols may have other definitions when used without the brackets.3.2 Definitions of Terms Specific to This
19、 Standard:3.2.1 balanced laminate, na continuous fiber-reinforced laminate in which each + lamina, measured with respect to thelaminate reference axis, is balanced by a lamina of the same material (for example, 0/+45/45/+45/45/0).3.2.2 short-beam strength, nthe shear stress as calculated in Eq 1, de
20、veloped at the specimen mid-plane at the failure eventspecified in 11.6.3.2.2.1 DiscussionAlthough shear is the dominant applied loading in this test method, the internal stresses are complex and a variety of failure modescan occur. Elasticity solutions by Berg et al (1)4, Whitney (2), and Sullivan
21、and Van Oene (3) have all demonstrated inadequaciesin classical beam theory in defining the stress state in the short-beam configuration. These solutions show that the parabolicshear-stress distribution as predicted by Eq 1 only occurs, and then not exactly, on planes midway between the loading nose
22、 andsupport points.Away from these planes, the stress distributions become skewed, with peak stresses occurring near the loading noseand support points. Of particular significance is the stress state local to the loading nose in which the severe shear-stressconcentration combined with transverse and
23、 in-plane compressive stresses has been shown to initiate failure. However, for themore ductile matrices, plastic yielding may alleviate the situation under the loading nose (1) and allow other failure modes to occursuch as bottom surface fiber tension (2). Consequently, unless mid-plane interlamina
24、r failure has been clearly observed, theshort-beam strength determined from this test method cannot be attributed to a shear property, and the use of Eq 1 will not yieldan accurate value for shear strength.3.2.3 symmetric laminate, na continuous fiber-reinforced laminate in which each ply above the
25、mid-plane is identicallymatched (in terms of position, orientation, and mechanical properties) 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
26、test.ximeasured or derived property for an individual specimen from the sample population.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 on twosupports that allow lateral motion, the lo
27、ad being applied by means of a loading nose directly centered on the midpoint of the testspecimen.5. Significance and Use5.1 In most cases, because of the complexity of internal stresses and the variety of failure modes that can occur in this specimen,it is not generally possible to relate the short
28、-beam strength to any one material property. However, failures are normally dominatedby resin and interlaminar properties, and the test results have been found to be repeatable for a given specimen geometry, materialsystem, and stacking sequence (4).5.2 Short-beam strength determined by this test me
29、thod can be used for quality control and process specification purposes. Itcan also be used for comparative testing of composite materials, provided that failures occur consistently in the same mode (5).4 Boldface numbers in parentheses refer to the list of references at the end of this standard.D23
30、44/D2344M 1625.3 This test method is not limited to specimens within the range specified in Section 8, but is limited to the use of a loadingspan length-to-specimen thickness ratio of 4.0 and a minimum specimen thickness of 2.0 mm 0.08 in.6. Interferences6.1 Accurate reporting of observed failure mo
31、des is essential for meaningful data interpretation, in particular, the detection ofinitial damage modes.7. Apparatus7.1 Testing Machine, properly calibrated, which can be operated at a constant rate of crosshead motion, and which the error inthe loading system shall not exceed 61 %. The load-indica
32、ting mechanism shall be essentially free of inertia lag at the crossheadrate used. Inertia lag may not exceed 1 % of the measured load. The accuracy of the testing machine shall be verified in accordancewith Practices E4.7.2 Loading Nose and Supports, as shown in Figs. 5 and 6, shall be 6.00 6 0.50
33、mm 0.250 6 0.020 in. and 3.00 6 0.40 mm0.125 6 0.010 in. diameter cylinders, respectively, with a hardness of 60 to 62 HRC, as specified in Test Methods E18, and shallhave finely ground surfaces free of indentation and burrs with all sharp edges relieved. The loading configuration shown in Fig.5 is
34、recommended for curved specimens with a radius r to specimen thickness h ratio of r/h of 5 or less. The loading configurationshown in Fig. 6 is recommended for flat specimens as well as curved specimens with a r/h ratio of greater than 5.7.3 MicrometersMicrometers and CalipersFor width and thickness
35、 measurements, the micrometers shall use a 4- to 5-mm(0.16- to 0.2-in.) A micrometer with a 4 to 7 mm 0.16 to 0.28 in. nominal diameter ball interface on an irregular surface suchas the bag side of a laminate and a or a flat anvil interface on machined edges or very smooth tooled surfaces.shall be u
36、sed tomeasure the specimen width and thickness.Aball interface is recommended for thickness measurements when at least one surfaceis irregular (e.g. a coarse peel ply surface which is neither smooth nor flat).Amicrometer or caliper with a flat anvil facesinterfaceshall be used to measure the length
37、of the specimen. for measuring length. The use of alternative measurement devices is permittedif specified (or agreed to) by the test requestor and reported by the testing laboratory. The accuracy of the instrument(s) shall besuitable for reading to within 1 % 1 % of the samplespecimen dimensions. F
38、or typical sectionspecimen geometries, an instrumentwith an accuracy of 60.002 mm (60.0001 in.) is desirable for thickness and width measurement,60 .0025 mm 60.0001 in. isNOTE 1Drawing interpretation per ANSI Y14.5-1982 and ANSI/ASM B46.1-1986.NOTE 2Ply orientation tolerance 60.5 relative to B.FIG.
39、1 Flat Specimen Configuration (SI)D2344/D2344M 163adequate for width and thickness measurements, while an instrument with an accuracy of 60.160.025 mm (60.004 in.)60.001in. is adequate for length measurement.measurement of length.7.4 Conditioning Chamber, when conditioning materials at nonlaboratory
40、 environments, a temperature/vapor-level-controlledenvironmental conditioning chamber is required that shall be capable of maintaining the required temperature to within 63C(65F) and the required vapor level to within 63 %. Chamber conditions shall be monitored either on an automated continuousbasis
41、 or on a manual basis at regular intervals.7.5 Environmental Test Chamber, an environmental test chamber is required for test environments other than ambient testinglaboratory conditions. This chamber shall be capable of maintaining the test specimen at the required test environment during themechan
42、ical test method.8. Sampling and Test Specimens8.1 SamplingTest at least five specimens per test condition unless valid results can be gained through the use of fewerspecimens, as in the case of a designed experiment. For statistically significant data, consult the procedures outlined in PracticeE12
43、2. Report the method of sampling.8.2 Geometry:8.2.1 Laminate ConfigurationsBoth multidirectional and pure unidirectional laminates can be tested, provided that there areat least 10 % 0 fibers in the span direction of the beam (preferably well distributed through the thickness), and that the laminate
44、sare both balanced and symmetric with respect to the span direction of the beam.8.2.2 Specimen ConfigurationsTypical configurations for the flat and curved specimens are shown in Figs. 1-4. For specimenthicknesses other than those shown, the following geometries are recommended:Specimen length = thi
45、ckness 6Specimen width, b = thickness 2.0NOTE 2A discussion of width-to-thickness effects is available in Adams and Lewis (6).8.2.2.1 For curved beam specimens, it is recommended that the arc should not exceed 30. Also, for these specimens, thespecimen length is defined as the minimum chord length.N
46、OTE 1Drawing interpretation per ANSI Y14.5-1982 and ANSI/ASME B46.1-1986.NOTE 2Ply orientation tolerance 60.5 relative to B.FIG. 2 Flat Specimen Configuration (Inch Pound)D2344/D2344M 1648.3 Specimen PreparationGuide D5687/D5687M provides recommended specimen preparation practices and should befollo
47、wed where practical.8.3.1 Laminate FabricationLaminates may be hand-laid, filament-wound or tow-placed, and molded by any suitablelaminating means, such as press, bag, autoclave, or resin transfer molding.8.3.2 Machining MethodsSpecimen preparation is important for these specimens. Take precautions
48、when cutting specimensfrom the rings or plates to avoid notches, undercuts, rough or uneven surfaces, or delaminations as a result of inappropriatemachining methods. Obtain final dimensions by water-lubricated precision sawing, milling, or grinding. The use of diamondtooling has been found to be ext
49、remely effective for many material systems. Edges should be flat and parallel within the specifiedtolerances.8.3.3 LabelingLabel the specimens so that they will be distinct from each other and traceable back to the raw material, in amanner that will both be unaffected by the test method and not influence the test method.9. Calibration9.1 The accuracy of all measuring equipment shall have certified calibrations that are current at the time of use of the equipment.NOTE 1Drawing interpretation per A
