1、Designation: D3518/D3518M 94 (Reapproved 2007)D3518/D3518M 13Standard Test Method forIn-Plane Shear Response of Polymer Matrix CompositeMaterials by Tensile Test of a 645 Laminate1This standard is issued under the fixed designation D3518/D3518M; the number immediately following the designation indic
2、ates theyear of original adoption or, 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
3、the Department of Defense.1. Scope1.1 This test method determines the in-plane shear response of polymer matrix composite materials reinforced by high-modulusfibers. The composite material form is limited to a continuous-fiber-reinforced composite 645 laminate capable of being tensiontested in the l
4、aminate x direction.1.2 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 u
5、se.1.2 The values stated in either SI units or inch-pound units are to be 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 v
6、alues from the two systems may result in nonconformance with the standard.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
7、 the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD3039/D3039M Test Method for Tensile Properties of Polymer Matrix Composite MaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture
8、 Absorption Properties and Equilibrium Conditioning of Polymer Matrix CompositeMaterialsE6 Terminology Relating to Methods of Mechanical TestingE111 Test Method for Youngs Modulus, Tangent Modulus, and Chord ModulusE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE456 Termin
9、ology Relating to Quality and StatisticsE1309 Guide for Identification of Fiber-Reinforced Polymer-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 Core Mat
10、erials in Computerized Material Property Databases3. 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 P
11、racticeE177 define terms relating to statistics. In the event of a conflict between terms, Terminology D3878 shall have precedence overthe other standards.3.2 Definitions of Terms Specific to This Standard:1 This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and
12、is the direct responsibility of Subcommittee D30.04 on Lamina andLaminate Test Methods.Current edition approved May 1, 2007Aug. 1, 2013. Published June 2007 September 2013. Originally approved in 1976. Last previous edition approved in 20012007 asD3518/D3518M 94(2001).(2007). DOI: 10.1520/D3518_D351
13、8M-94R07.10.1520/D3518_D3518M-13.2 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 Document Summary page on the ASTM website.This document is not an ASTM
14、 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. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all
15、 cases only the current 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 States1NOTE 1If the term represents a physical quantity, its analytical dimensions
16、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,L for length, T for time, for thermodynamic temperature, and nd for nondimensional quantities. U
17、se of these symbols is restricted to analyticaldimensions when used with square brackets, as the symbols may have other definitions when used without the brackets.3.2.1 645 laminatein laminated composites, a balanced, symmetric lay-up composed only of +45 plies and 45 plies. (Seealso ply orientation
18、.)3.2.2 balanced, adjin laminated composites, having, for every off-axis ply oriented at +, another ply oriented at that isof the same material system and form.3.2.3 lamina, npl. laminae, in laminated composites, a single, thin, uniform layer that is the basic building block of a laminate.(Syn. ply
19、).3.2.4 material coordinate system, nin laminated composites, a 123 Cartesian coordinate system describing the principlematerial coordinate system for a laminated material, where the 1-axis is aligned with the ply principal axis, as illustrated in Fig.1. (See also ply orientation, ply principal axis
20、, and principal material coordinate system.)3.2.5 nominal value, na value, existing in name only, assigned to a measurable property for the purpose of convenientdesignation. Tolerances may be applied to a nominal value to define an acceptable range for the property.3.2.6 off-axis, adjin laminated co
21、mposites, having a ply orientation that is neither 0 nor 90.3.2.7 ply, nin laminated composites, synonym for lamina.3.2.8 ply orientation, n, in laminated composites, the angle between a reference direction and the ply principal axis. Theangle is expressed in degrees, greater than 90 but less than o
22、r equal to +90, and is shown as a positive quantity when taken fromthe reference direction to the ply principal axis, following the right-hand rule.3.2.8.1 DiscussionThe reference direction is usually related to a primary load-carrying direction.3.2.9 ply principal axis, nin laminated composites, th
23、e coordinate axis in the plane of each lamina that defines the plyorientation. (See also ply orientation and material coordinate system.)3.2.9.1 DiscussionThe ply principal axis will, in general, be different for each ply of a laminate.The angle that this axis makesrelative to a reference axis is gi
24、ven by the ply orientation. The convention is to align the ply principal axis with the direction ofmaximum stiffness (for example, the fiber direction of unidirectional tape or the warp direction of fabric reinforced material).3.2.10 principal material coordinate system, na coordinate system having
25、axes that are normal to planes of symmetry withinthe material. (See also material coordinate system.)3.2.10.1 DiscussionCommon usage, at least for Cartesian coordinate systems (for example, 123 or xyz), aligns the first axisof the principal material coordinate system with the direction of highest pr
26、operty value; for elastic properties, the axis of greatestelastic modulus is aligned with the 1 or x axes.3.2.11 symmetric, adjin laminated composites, when the constituents, material form, and orientation for the plies located onone side of the laminate midplane are the mirror image of the plies on
27、 the other side of the midplane.3.2.12 transition region, na strain region of a stress-strain or strain-strain curve over which a significant change in the slopeof the curve occurs within a small strain range.3.2.12.1 DiscussionMany filamentary composite materials exhibit a nonlinear stress/strain r
28、esponse during loading, such asseen in plots of either longitudinal stress versus longitudinal strain or transverse strain versus longitudinal strain. In certain cases,the nonlinear response may be conveniently approximated by a bilinear fit. There are varying physical reasons for the existenceof a
29、transition region. Common examples include matrix cracking under tensile loading and ply delamination.3.3 Symbols:3.3.1 Across-sectional area of a coupon.3.3.2 CVcoefficient of variation statistic of a sample population for a given property (in percent).FIG. 1 Material Coordinate SystemD3518/D3518M
30、1323.3.3 F12 (offset)the value of the 12 shear stress at the intersection of the shear chord modulus of elasticity and the stressstress stress-strain curve, when the modulus is offset along the engineering shear strain axis from the origin by the reported strainoffset value.3.3.4 G12in-plane shear m
31、odulus of elasticity.3.3.4.1 DiscussionIndices 1 and 2 indicate the fiber direction and transverse to the fiber direction in the plane of the ply, respectively, as illustratedin Fig. 2.3.3.5 nnumber of coupons per sample population.3.3.6 Ploadforce carried by test coupon.3.3.7 Pmthe loadforce carrie
32、d by test coupon that is the lesser of the (1) maximum loadforce before failure or (2) loadforceat 5 % engineering shear strain.3.3.8 sn1standard deviation statistic of a sample population for a given property.3.3.9 itest result for an individual coupon from the sample population for a given propert
33、y.3.3.10 xmean or average (estimate of mean) of a sample population for a given property.3.3.11 general symbol for strain, whether normal strain or shear strain.3.3.12 indicated normal strain from strain transducer or extensometer.3.3.13 12shear stress on the plane perpendicular to the 1-axis that a
34、cts parallel to the 2-axis.3.3.14 12mthe calculated value of the 12 shear stress taken at the lesser of (1) maximum shear stress before failure or (2) shearstress at 5 % engineering shear strain.3.3.15 12engineering shear strain on the plane perpendicular to the 1-axis that acts parallel to the 2-ax
35、is.3.3.16 12mthe value of the 12 engineering shear strain at the maximum shear stress before failure, or 5 %, whichever is less.4. Summary of Test Method4.1 A uniaxial tension test of a 645 laminate is performed in accordance with Test Method D3039/D3039M, although withspecific restrictions on stack
36、ing sequence and thickness. Use of this test for evaluation of in-plane shear response was originallyproposed by Petit3 and was later improved by Rosen.4 Using expressions derived from laminated plate theory, the in-plane shear3 Petit, D. H., “A Simplified Method of Determining the In-plane Shear St
37、ress/Strain Response of Unidirectional Composites,” Composite Materials: Testing and Design,ASTM STP 460, American Society for Testing and Materials, 1969, pp. 8393.4 Rosen, B. W., “ASimple Procedure for Experimental Determination of the Longitudinal Shear Modulus of Unidirectional Composites,” Jour
38、nal of Composite Materials,October 1972, pp. 552554.FIG. 2 Definition of Specimen and Material AxesD3518/D3518M 133stress in the material coordinate system is directly calculated from the applied axial load,force, and the related shear stressstrainis determined from longitudinal and transverse norma
39、l strain data obtained by transducers. This data is used to create an in-planeshear stress-shear strain curve.5. Significance and Use5.1 This test method is designed to produce in-plane shear property data for material specifications, research and development,quality assurance, and structural design
40、 and analysis. Factors that influence the shear response and should therefore be reportedinclude the following: material, methods of material preparation and lay-up, specimen stacking sequence and overall thickness,specimen preparation, specimen conditioning, environment of testing, specimen alignme
41、nt and gripping, speed of testing, time attemperature, void content, and volume percent reinforcement. Properties that may be derived from this test method include thefollowing:5.1.1 In-plane shear stress versus shear strain response,5.1.2 In-plane shear chord modulus of elasticity,5.1.3 Offset shea
42、r properties,5.1.4 Maximum in-plane shear stress for a 645 laminate, and5.1.5 Maximum in-plane engineering shear strain for a 645 laminate.6. Interferences6.1 Impurity of Stress FieldThe material in the gage section of this specimen is not in a state of pure in-plane shear stress,as an in-plane norm
43、al stress component is present throughout the gage section and a complex stress field is present close to thefree edges of the specimen. Although this test method is believed to provide reliable initial material response and can establishshear stress-shear strain response well into the nonlinear reg
44、ion, the calculated shear stress values at failure do not represent truematerial strength values and should only be used with caution. Despite attempts to minimize these effects, the shear stress at failureobtained from this test method, even for otherwise identical materials that differ only in cur
45、ed ply thickness or fabric areal weight,may have differing failure modes and may not be able to be statistically pooled.The technical basis for the further discussion belowis taken from the paper by Kellas et al.56.1.1 Effects of In-Plane Normal Stress FieldOf particular concern is the in-plane stre
46、ss component normal to the fiberdirection. This component of stress is present in all plies and throughout the gage section of the specimen. The effect of this stresson a given ply is minimized by the fiber reinforcement of the neighboring plies. Since the ply constraint is reduced with increasingpl
47、y thickness, the thickness of the individual plies is an important parameter that influences both the shear stress-shear strainresponse and the ultimate failure loadforce of this specimen.6 Moreover, the surface plies of a given specimen, being constrainedby only one neighboring ply (as opposed to i
48、nterior plies, which are constrained by a ply on each side), represent the weakest linkin a 645 specimen. During the tensile loading of this test coupon, the first ply failures consist primarily of normal stress (or mixedmode) failures, rather than pure shear failures. Because of this, the actual ma
49、terial shear strength cannot be obtained from this test.Except for the case of materials capable of sustaining large axial test coupon strains (greater than about 3.0 %), the shear stressat failure is believed to underestimate the actual material shear strength.6.1.2 Total Thickness EffectsAs a result of the failure processes discussed above, the shear stress-shear strain response athigher strain levels depends upon the total number of plies.As the total number of plies in the specimen configur
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