1、Designation: D 7078/D 7078M 05Standard Test Method forShear Properties of Composite Materials by V-Notched RailShear Method1This standard is issued under the fixed designation D 7078/D 7078M; the number immediately following the designation indicates theyear of original adoption or, in the case of r
2、evision, the 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 covers the determination of the shearproperties of high-modulus fiber-reinforce
3、d composite materi-als by clamping the ends of a V-notched specimen between twopairs of loading rails. When loaded in tension, the railsintroduce shear forces into the specimen through the specimenfaces. In comparison, the specimen of Test Method D 5379/D 5379M is loaded through its top and bottom e
4、dges. Faceloading allows higher shear forces to be applied to thespecimen, if required. Additionally, the present test methodutilizes a specimen with a larger gage section than theV-notched specimen of Test Method D 5379/D 5379M. In bothtest methods, the use of a V-notched specimen increases thegage
5、 section shear stresses in relation to the shear stresses inthe vicinity of the grips, thus localizing the failure within thegage section while causing the shear stress distribution to bemore uniform than in a specimen without notches. In compari-son, Test Method D 4255/D 4255M utilizes an unnotched
6、specimen clamped between two pairs of loading rails that areloaded in tension. Also in contrast to Test Method D 4255/D 4255M, the present test method provides specimen grippingwithout the need for holes in the specimen.The composite materials are limited to continuous-fiber ordiscontinuous-fiber-re
7、inforced composites in the following ma-terial forms:1.1.1 Laminates composed only of unidirectional fibrouslaminae, with the fiber direction oriented either parallel orperpendicular to the fixture rails.1.1.2 Laminates of balanced and symmetric construction,with the 0 direction oriented either para
8、llel or perpendicular tothe fixture rails.1.1.3 Laminates composed of woven, braided, or knittedfabric filamentary laminae.1.1.4 Short-fiber-reinforced composites with a majority ofthe fibers being randomly distributed.1.2 The values stated in either SI units or inch-pound unitsare to be regarded se
9、parately as standard. Within the text theinch-pound units are shown in brackets. The values stated 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.1.3 This stand
10、ard does not purport to address all of thesafety concerns, if any, associated with its use. It 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 AS
11、TM Standards:2D 792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD 883 Terminology Relating to PlasticsD 2584 Test Method for Ignition Loss of Cured ReinforcedResinsD 2734 Test Methods for Void Content of Reinforced Plas-ticsD 3171 Test Methods for Con
12、stituent Content of CompositeMaterialsD 3878 Terminology for Composite MaterialsD 4255/D 4255M Test Method for In-Plane Shear Proper-ties of Polymer Matrix Composite Materials by the RailShear MethodD 5229/D 5229M Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer
13、Ma-trix Composite MaterialsD 5379/D 5379M Test Method for Shear Properties ofComposite Materials by the V-Notched Beam MethodD 6856 Guide for Testing Fabric-Reinforced Textile Com-posite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical
14、Test-ingE 111 Test Method for Youngs Modulus, Tangent Modulus,and Chord ModulusE 122 Practice for Calculating of Sample Size to Estimate,1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.04 onLamina and Lamina
15、te Test Methods.Current edition approved May 15, 2005. Published August 2005.2For 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 ont
16、he ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.With a Specified Tolerable Error, the Average for Charac-teristic of a Lot or ProcessE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 251 Test
17、 Methods for Performance Characteristics ofMetallic Bonded Resistance Strain GagesE 456 Terminology Relating to Quality and StatisticsE 1237 Guide for Installing Bonded Resistance StrainGagesE 1309 Guide for Identification of Fiber-Reinforced Poly-mer Matrix Composite Materials in DatabasesE 1434 Gu
18、ide for Mechanical Test Data of Fiber-ReinforcedComposite Materials in Databases2.2 Other Documents:ANSI Y14.5M-1982 Geometric Dimensioning and Toler-ancing3ANSI/ASME B 46.1-1985 Surface Texture (Surface Rough-ness, Waviness, and Lay)32.3 ASTM Adjuncts:V-Notched Rail Shear Fixture Machining Drawings
19、43. Terminology3.1 DefinitionsTerminology D 3878 defines terms relatingto high-modulus fibers and their composites. TerminologyD 883 defines terms relating to plastics. Terminology E6defines terms relating to mechanical testing. TerminologyE 456 and Practice E 177 define terms relating to statistics
20、. Inthe event of a conflict between terms, Terminology D 3878shall have precedence over the other terminology standards.NOTE 1If the term represents a physical quantity, its analyticaldimensions are stated immediately following the term (or letter symbol) infundamental dimension form, using the foll
21、owing ASTM standard sym-bology for fundamental dimensions, shown within square brackets: Mfor mass, L for length, T for time, Q for thermodynamic temperature,and nd for nondimensional quantities. Use of these symbols is restrictedto analytical dimensions when used with square brackets, as the symbol
22、smay have other definitions when used without the brackets.3.2 Definitions of Terms Specific to This Standard:3.2.1 in-plane shear, nshear associated with shear forcesor deformation applied to the 1-2 material plane such that theresulting shear deformations occur in the plane of the laminate.(See al
23、so material coordinate system).3.2.2 interlaminar shear, nany of the shear propertiesdescribing the response resulting from a shear load or defor-mation applied to the 1-3 or 2-3 material planes. (See alsomaterial coordinate system).3.2.3 material coordinate system, na Cartesian coordinatesystem des
24、cribing the principal material coordinate systemusing 1, 2, and 3 for the axes, as shown in Fig. 1.3.2.4 offset shear strength M/(LT2), nthe shear stress amaterial sustains at the intersection of the shear stress versusengineering shear strain curve with a line parallel to a definedmodulus and trans
25、lated from the origin by a specified strain.3.2.4.1 DiscussionThe offset shear strength is a measureof the extent of material stress/strain linearity. (The materialnon-linearity in this definition neither assumes nor prohibits thepresence of damage.) When comparing material offsetstrengths the same
26、offset strain and modulus definition shouldbe used. For material comparison in the absence of evidencesuggesting the use of more appropriate values, an offset strainof 0.2 % should be used with the standard chord modulus. Agraphical example of offset shear strength is shown in Fig. 2.For design, oth
27、er offset strain and modulus definition combi-nations may be more suitable for specific materials andapplications.3.2.5 shear strength M/(LT2), nthe shear stress carriedby a material at failure under a pure shear condition.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
28、4th Floor, New York, NY 10036.4Available from ASTM Headquarters, 100 Barr Harbor Dr., PO Box C700, WestConshohocken, PA 19428-2959. Order Adjunct ADJD7078.FIG. 1 Material Coordinate SystemD 7078/D 7078M 0523.3 Symbols:A = cross-sectional area of a specimenCV = coefficient of variation statistic of a
29、 samplepopulation for a given property (in percent)d1= coupon width between notchesd2= notch depthFsu= ultimate shear strength in the test directionFu= ultimate strength in the test directionF (offset) = the value of the shear stress at the intersectionof the shear chord modulus of elasticity andthe
30、 stress strain curve, when the modulus isoffset along the shear strain axis from theorigin by the reported strain offset valueG = shear modulus of elasticity in the test directionh = overall coupon thicknessL = overall coupon lengthn = number of coupons per sample populationP = load carried by test
31、couponPf= load carried by test coupon at failurePmax= maximum load carried by test coupon beforefailurer = notch radiusSn-1= standard deviation statistic of a sample popu-lation for a given propertyw = overall coupon widthxi= test result for an individual specimen from thesample population for a giv
32、en propertyX= mean or average (estimate of mean) of asample population for a given propertyg = engineering shear straine = indicated normal strain from strain transduceror extensometers = normal stresst = shear stressu = ply orientation angle4. Summary of Test Method4.1 A material coupon in the form
33、 of a flat rectangle withsymmetrical centrally located V-notches, shown schematicallyin Fig. 3, is clamped to two fixture halves (pictured in Fig. 4,and shown schematically in Fig. 5 and in more detail in themachining drawings of ASTM Adjunct ADJD7078).5Whenloaded in tension using a mechanical testi
34、ng machine, thisfixture introduces shear forces in the specimen that producefailures across the notched specimen.4.2 The specimen is inserted into the two fixture halves withthe notches located along the line of the applied load. The twohalves of the assembled fixture are extended by a testingmachin
35、e while monitoring load. The relative displacementbetween the two fixture halves produces shear stresses in thenotched specimen. By placing two strain gage elements,oriented at 645 to the loading axis, in the middle of thespecimen and along the loading axis, the shear strain responseof the material
36、can be measured.4.3 The notches influence the shear strain distribution in thecentral region of the coupon, producing a more uniformdistribution than without notches. As a result of the reducedspecimen width due to the notches, the average shear stress isincreased relative to the unnotched width.5.
37、Significance and Use5.1 This shear test is designed to produce shear propertydata for material specifications, research and development,quality assurance, and structural design and analysis. Eitherin-plane or interlaminar shear properties may be evaluated,depending upon the orientation of the materi
38、al coordinatesystem relative to the loading axis. Factors that influence theshear response and should therefore be reported include:material, methods of material preparation and lay-up, specimenstacking sequence, specimen preparation, specimen condition-ing, environment of testing, specimen alignmen
39、t and gripping,speed of testing, time at temperature, void content, and volumepercent reinforcement.5.2 In anisotropic materials, properties may be obtained inany of the six possible shear planes by orienting the testingplane of the specimen with the desired material plane (1-2 or2-1, 1-3 or 3-1, 2-
40、3 or 3-2). Only a single shear plane may beevaluated for any given specimen. Properties, in the testdirection, which may be obtained from this test method,include the following:5The fixture and specimen were developed at the University of Utah (1-3). Thiswork followed an earlier investigation on an
41、improved rail shear test method at theUniversity of Wyoming Composite Materials Research Group (4 and 5). Thenumbers in parentheses refer to the references listed at the end of the standard.FIG. 2 Illustration of Modulus and Offset Strength DeterminationD 7078/D 7078M 0535.2.1 Shear stress versus en
42、gineering shear strain response,5.2.2 Ultimate shear strength,5.2.3 Ultimate engineering shear strain,5.2.4 Shear chord modulus of elasticity,5.2.5 Transition strain.Nominal Specimen Dimensionsd1= 31.0 mm 1.20 in.d2= 12.7 mm 0.50 in.h = as requiredL = 76.0 mm 3.0 in.r = 1.3 mm 0.05 in.w = 56.0 mm 2.
43、20 in.FIG. 3 V-Notched Rail Shear Test Specimen SchematicFIG. 4 Partially Assembled Fixture with Specimen and Spacer BlocksD 7078/D 7078M 0546. Interferences6.1 Material and Specimen PreparationPoor materialfabrication practices, lack of control of fiber alignment, anddamage induced by improper spec
44、imen machining are knowncauses of high material data scatter in composites.6.2 Elastic Modulus MeasurementShear modulus calcu-lations in this test method assume a uniform distribution ofshear stress and shear strain in the region of the specimenbetween the notch tips. The actual uniformity is depend
45、ent onthe material orthotropy, the direction of loading, and the notchgeometry (notch angle, notch depth, and notch radius). Refer-ring to the fiber orientations in Fig. 6, detailed stress analysis(1)6has shown that 0nspecimens produce an elastic modulusmeasurement that is too high (5-10 % too high
46、for carbon/epoxy), whereas 0/90nsspecimens produce a relatively accu-rate elastic modulus measurement. Further, stress analysis hasshown that specimens with between 25 % and 100 % 645plies produce relatively accurate elastic laminate modulusmeasurements.6.3 Specimen Geometry ModificationsVariations
47、in thenotch geometry (notch angle, notch depth, and notch radius)affect the degree of nonuniformity of shear stress and shearstrain in the region of the specimen between the notches.Recommendations for notch dimensions versus the degree ofmaterial orthotropy have not been fully developed. Thus, asin
48、gle notch geometry has been adopted. Variations to thenotch angle, notch depth, and notch radius for the purpose ofincreasing the uniformity of the shear stress/shear straindistributions for a particular material and laminate are accept-able when the variations are clearly noted in the report.6.4 Lo
49、ad EccentricityTwisting of the specimen duringloading can occur, affecting strength results, and especiallyelastic modulus measurement. Twisting may occur due to anout-of-tolerance fixture, an out-of-tolerance specimen, or froma specimen that is improperly installed in the fixture. It isrecommended that at least one specimen of each sample betested with back-to-back two-element strain gages to evaluatethe degree of twist. Evaluate the percent twist for the specimenby substituting the shear modulus from each side, Gaand Gb,into | (Ga Gb
