1、Designation: D7078/D7078M 05 D7078/D7078M 12Standard Test Method forShear Properties of Composite Materials by V-Notched RailShear Method1This standard is issued under the fixed designation D7078/D7078M; the number immediately following the designation indicates theyear of original adoption or, in t
2、he 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.1. Scope1.1 This test method covers the determination of the shear properties of high-modulus fib
3、er-reinforced composite materials byclamping the ends of a V-notched specimen between two pairs of loading rails. When loaded in tension, the rails introduce shearforces into the specimen through the specimen faces. In comparison, the specimen of Test Method D5379/D5379M is loadedthrough its top and
4、 bottom edges. Face loading allows higher shear forces to be applied to the specimen, if required. Additionally,the present test method utilizes a specimen with a larger gage section than the V-notched specimen of Test MethodD5379/D5379M. In both test methods, the use of a V-notched specimen increas
5、es the gage section shear stresses in relation to theshear stresses in the vicinity of the grips, thus localizing the failure within the gage section while causing the shear stressdistribution to be more uniform than in a specimen without notches. In comparison, Test Method D4255/D4255M utilizes anu
6、nnotched specimen clamped between two pairs of loading rails that are loaded in tension. Also in contrast to Test MethodD4255/D4255M, the present test method provides specimen gripping without the need for holes in the specimen.The composite materials are limited to continuous-fiber or discontinuous
7、-fiber-reinforced composites in the following materialforms:1.1.1 Laminates composed only of unidirectional fibrous laminae, 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 ei
8、ther parallel or perpendicular to thefixture rails.1.1.3 Laminates composed of woven, braided, or knitted fabric filamentary laminae.1.1.4 Short-fiber-reinforced composites with a majority of the fibers being randomly distributed.1.2 The values stated in either SI units or inch-pound units are to be
9、 regarded separately as standard. Within the text theinch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system mustbe used independently of the other. Combining values from the two systems may result in nonconformance with the standard
10、.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its 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 Do
11、cuments2.1 ASTM Standards:2D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics 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
12、for Constituent Content of Composite MaterialsD3878 Terminology for Composite MaterialsD4255/D4255M Test Method for In-Plane Shear Properties of Polymer Matrix Composite Materials by the Rail Shear Method1 This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is
13、 the direct responsibility of Subcommittee D30.04 on Lamina andLaminate Test Methods.Current edition approved May 15, 2005July 15, 2012. Published August 2005December 2012. Originally approved in 2005. Last previous edition approved in 2005 asD7078/D7078M-05. DOI: 10.1520/D7078_D7078M-05.10.1520/D70
14、78_D7078M-12.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is
15、intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit 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 c
16、urrent versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1D5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of P
17、olymer Matrix CompositeMaterialsD5379/D5379M Test Method for Shear Properties of Composite Materials by the V-Notched Beam MethodD6856 Guide for Testing Fabric-Reinforced “Textile” Composite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechani
18、cal TestingE111 Test Method for Youngs Modulus, Tangent Modulus, and Chord ModulusE122 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 MethodsE251 Test Me
19、thods for Performance Characteristics of Metallic Bonded Resistance Strain GaugesE456 Terminology Relating to Quality and StatisticsE1237 Guide for Installing Bonded Resistance Strain GagesE1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in DatabasesE1434 Guide f
20、or Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases2.2 Other Documents:ANSI Y14.5M-1982 Geometric Dimensioning and Tolerancing3ANSI/ASME B 46.1-1985 Surface Texture (Surface Roughness, Waviness, and Lay)32.3 ASTM Adjuncts:V-Notched Rail Shear Fixture Machining Draw
21、ings43. Terminology3.1 DefinitionsTerminology D3878 defines terms relating to high-modulus fibers 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 statisti
22、cs. In the event of a conflict between terms, Terminology D3878 shall have precedence overthe other terminology standards.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 f
23、ollowing ASTM standard symbology for fundamental dimensions, shown within square brackets: M for mass,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 symbo
24、ls may 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 forces or deformation applied to the 1-2 material plane such that theresulting shear deformations occur in the plane of the laminate. (Se
25、e also material coordinate system).3.2.2 interlaminar shear, nany of the shear properties describing the response resulting from a shear loadforce or deformationapplied to the 1-3 or 2-3 material planes. (See also material coordinate system).3.2.3 material coordinate system, na Cartesian coordinate
26、system describing the principal material coordinate system using1, 2, and 3 for the axes, as shown in Fig. 1.3.2.4 offset shear strength M/(LT2), nthe shear stress a material sustains at the intersection of the shear stress versusengineering shear strain curve with a line parallel to a defined modul
27、us and translated from the origin by a specified strain.3.2.4.1 DiscussionThe offset shear strength is a measure of the extent of material stress/strain linearity. (The material non-linearity in this definitionneither assumes nor prohibits the presence of damage.) When comparing material offset stre
28、ngths the same offset strain andmodulus definition should be used. For material comparison in the absence of evidence suggesting the use of more appropriatevalues, an offset strain of 0.2 % should be used with the standard chord modulus. A graphical example of offset shear strength isshown in Fig. 2
29、. For design, other offset strain and modulus definition combinations may be more suitable for specific materialsand applications.3.2.5 shear strength M/(LT2), nthe shear stress carried by a material at failure under a pure shear condition.3.3 Symbols:A = cross-sectional area of a specimenCV = coeff
30、icient of variation statistic of a sample population for a given property (in percent)3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.4 Available from ASTM Headquarters, 100 Barr Harbor Dr., PO Box C700, West Conshohocken, PA 19428-2959. O
31、rder Adjunct ADJD7078.D7078/D7078M 122d1 = 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 intersection of the shear chord modulus of elasticity and the stress
32、 strain curve,when the modulus is offset along the shear strain axis from the origin by the reported strain offset valueF (offset) = the value of the shear stress at the intersection of the shear chord modulus of elasticity and the stress-strain curve,when the modulus is offset along the shear strai
33、n axis from the origin 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 couponP = force carried by test couponPf = load carried by test coup
34、on at failurePf = force carried by test coupon at failureFIG. 2 Illustration of Modulus and Offset Strength DeterminationFIG. 1 Material Coordinate SystemD7078/D7078M 123Pmax = maximum load carried by test coupon before failurePmax = maximum force carried by test coupon before failurer = notch radiu
35、sSn-1 = standard deviation statistic of a sample population for a given propertyw = overall coupon widthxi = test result for an individual specimen from the sample population for a given propertyX = mean or average (estimate of mean) of a sample population for a given property = engineering shear st
36、rain = indicated normal strain from strain transducer or extensometer = normal stress = shear stress = ply orientation angle4. Summary of Test Method4.1 A material coupon in the form of a flat rectangle with symmetrical centrally located V-notches, shown schematically in Fig.3, is clamped to two fix
37、ture halves (pictured in Fig. 4, and shown schematically in Fig. 5 and in more detail in the machiningdrawings of ASTM Adjunct ADJD7078).5 When loaded in tension using a mechanical testing machine, this fixture introduces shearforces in the specimen that produce failures across the notched specimen.
38、4.2 The specimen is inserted into the two fixture halves with the notches located along the line of the applied load.force. Thetwo halves of the assembled fixture are extended by a testing machine while monitoring load.force. The relative displacementbetween the two fixture halves produces shear str
39、esses in the notched specimen. By placing two strain gage elements, oriented at645 to the loading axis, in the middle of the specimen and along the loading axis, the shear strain response of the material canbe measured.5 The fixture and specimen were developed at the University of Utah (1-1 and 23).
40、 This work followed an earlier investigation on an improved rail shear test method atthe University of Wyoming Composite Materials Research Group (43 and 54). The numbers in parentheses refer to the references listed at the end of the standard.Nominal Specimen Dimensionsd1 = 31.0 mm 1.20 in.d2 = 12.
41、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 2.20 in.FIG. 3 V-Notched Rail Shear Test Specimen SchematicD7078/D7078M 1244.3 The notches influence the shear strain distribution in the central region of the coupon, producing a more uniform distributionthan without notc
42、hes. As a result of the reduced specimen width due to the notches, the average shear stress is increased relativeto the unnotched width.5. Significance and Use5.1 This shear test is designed to produce shear property data for material specifications, research and development, qualityassurance, and s
43、tructural design and analysis. Either in-plane or interlaminar shear properties may be evaluated, depending uponthe orientation of the material coordinate system relative to the loading axis. Factors that influence the shear response and shouldtherefore be reported include: material, methods of mate
44、rial preparation and lay-up, specimen stacking sequence, specimenpreparation, specimen conditioning, environment of testing, specimen alignment and gripping, speed of testing, time attemperature, void content, and volume percent reinforcement.5.2 In anisotropic materials, properties may be obtained
45、in any of the six possible shear planes by orienting the testing planeof the specimen with the desired material plane (1-2 or 2-1,1-3 or 3-1,2-3 or 3-2). Only a single shear plane may be evaluated forany given specimen. Properties, in the test direction, which may be obtained from this test method,
46、include the following:5.2.1 Shear stress versus engineering shear strain response,FIG. 4 Partially Assembled Fixture with Specimen and Spacer BlocksFIG. 5 Assembled V-Notched Rail Shear ApparatusD7078/D7078M 1255.2.2 Ultimate shear strength,5.2.3 Ultimate engineering shear strain,5.2.4 Shear chord m
47、odulus of elasticity,5.2.5 Transition strain.6. Interferences6.1 Material and Specimen PreparationPoor material fabrication practices, lack of control of fiber alignment, and damageinduced by improper specimen machining are known causes of high material data scatter in composites.6.2 Elastic Modulus
48、 MeasurementShear modulus calculations in this test method assume a uniform distribution of shear stressand shear strain in the region of the specimen between the notch tips. The actual uniformity is dependent on the material orthotropy,the direction of loading, and the notch geometry (notch angle,
49、notch depth, and notch radius). Referring to the fiber orientationsin Fig. 6, detailed stress analysis (1)6 has shown that 0n specimens produce an elastic modulus measurement that is too high(5-10 % too high for carbon/epoxy), whereas 0/90ns specimens produce a relatively accurate elastic modulus measurement.Further, stress analysis has shown that specimens with between 25 % and 100 % 645 plies produce relatively accurate elasticlaminate modulus measurements.6.3 Specimen Geometry ModificationsVariations in the notch geometry
