1、Designation: D 3518/D 3518M 94 (Reapproved 2007)Standard Test Method forIn-Plane Shear Response of Polymer Matrix CompositeMaterials by Tensile Test of a 645 Laminate1This standard is issued under the fixed designation D 3518/D 3518M; the number immediately following the designation indicates theyea
2、r 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 (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Depart
3、ment of Defense.1. Scope1.1 This test method determines the in-plane shear responseof polymer matrix composite materials reinforced by high-modulus fibers. The composite material form is limited to acontinuous-fiber-reinforced composite 645 laminate capableof being tension tested in the laminate x d
4、irection.1.2 This standard 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.1.3 Th
5、e values stated in either SI units or inch-pound unitsare to be regarded separately 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 t
6、he two systems may result in nonconformance with thestandard.2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating to PlasticsD 3039/D 3039M Test Method for Tensile Properties ofPolymer Matrix Composite MaterialsD 3878 Terminology for Composite MaterialsD 5229/D 5229M Test Method for
7、 Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite MaterialsE6 Terminology Relating to Methods of Mechanical Test-ingE 111 Test Method forYoungs Modulus, Tangent Modulus,and Chord ModulusE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE
8、 456 Terminology Relating to Quality and StatisticsE 1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE 1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE 1471 Guide for Identification of Fibers, Fillers,
9、 and CoreMaterials in Computerized Material Property Databases3. 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. Terminolog
10、yE 456 and Practice E 177 define terms relating to statistics. Inthe event of a conflict between terms, Terminology D 3878shall have precedence over the other standards.3.2 Definitions of Terms Specific to This Standard:NOTE 1If the term represents a physical quantity, its analyticaldimensions are s
11、tated immediately following the term (or letter symbol) infundamental dimension form, using the following 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
12、of these symbols is restrictedto analytical dimensions when used with square brackets, as the symbolsmay 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.(See also ply orientation.)3.2
13、.2 balanced, adjin laminated composites, having, forevery off-axis ply oriented at +u, another ply oriented at u thatis of the same material system and form.3.2.3 lamina, npl. laminae, in laminated composites,asingle, thin, uniform layer that is the basic building block of alaminate. (Syn. ply).3.2.
14、4 material coordinate system, nin laminated compos-ites, a 123 Cartesian coordinate system describing the principlematerial coordinate system for a laminated material, where the1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of
15、 Subcommittee D30.04 onLamina and Laminate Test Methods.Current edition approved May 1, 2007. Published June 2007. Originallyapproved in 1976. Last previous edition approved in 2001 as D 3518/D 3518M 94(2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custom
16、er Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1-axis is aligned with the ply princi
17、pal axis, as illustrated inFig. 1. (See also ply orientation, ply principal axis, andprincipal material coordinate system.)3.2.5 nominal value, na value, existing in name only,assigned to a measurable property for the purpose of conve-nient designation. Tolerances may be applied to a nominalvalue to
18、 define an acceptable range for the property.3.2.6 off-axis, adjin laminated composites, having a plyorientation that is neither 0 nor 90.3.2.7 ply, nin laminated composites, synonym for lamina.3.2.8 ply orientation, n, uin laminated composites, theangle between a reference direction and the ply pri
19、ncipal axis.The angle is expressed in degrees, greater than 90 but lessthan or equal to +90, and is shown as a positive quantity whentaken from the reference direction to the ply principal axis,following the right-hand rule.3.2.8.1 DiscussionThe reference direction is usually re-lated to a primary l
20、oad-carrying direction.3.2.9 ply principal axis, nin laminated composites, thecoordinate axis in the plane of each lamina that defines the plyorientation. (See also ply orientation and material coordinatesystem.)3.2.9.1 DiscussionThe ply principal axis will, in general,be different for each ply of a
21、 laminate. The angle that this axismakes relative to a reference axis is given by the ply orienta-tion. The convention is to align the ply principal axis with thedirection of maximum stiffness (for example, the fiber direc-tion of unidirectional tape or the warp direction of fabricreinforced materia
22、l).3.2.10 principal material coordinate system, na coordi-nate system having axes that are normal to planes of symmetrywithin the material. (See also material coordinate system.)3.2.10.1 DiscussionCommon usage, at least for Cartesiancoordinate systems (for example, 123 or xyz), aligns the firstaxis
23、of the principal material coordinate system with thedirection of highest property value; for elastic properties, theaxis of greatest elastic modulus is aligned with the 1 or x axes.3.2.11 symmetric, adjin laminated composites, when theconstituents, material form, and orientation for the plies locate
24、don one side of the laminate midplane are the mirror image ofthe plies on the other side of the midplane.3.2.12 transition region, na strain region of a stress-strainor strain-strain curve over which a significant change in theslope of the curve occurs within a small strain range.3.2.12.1 Discussion
25、Many filamentary composite materi-als exhibit a nonlinear stress/strain response during loading,such as seen in plots of either longitudinal stress versuslongitudinal strain or transverse strain versus longitudinalstrain. In certain cases, the nonlinear response may be conve-niently approximated by
26、a bilinear fit. There are varyingphysical reasons for the existence of a transition region.Common examples include matrix cracking under tensileloading and ply delamination.3.3 Symbols:3.3.1 Across-sectional area of a coupon.3.3.2 CVcoefficient of variation statistic of a samplepopulation for a give
27、n property (in percent).3.3.3 F12 (offset)the value of the t12shear stress at theintersection of the shear chord modulus of elasticity and thestress stress curve, when the modulus is offset along the shearstrain axis from the origin by the reported strain offset value.3.3.4 G12in-plane shear modulus
28、 of elasticity.3.3.4.1 DiscussionIndices 1 and 2 indicate the fiber direc-tion and transverse to the fiber direction in the plane of the ply,respectively, as illustrated in Fig. 2.3.3.5 nnumber of coupons per sample population.3.3.6 Pload carried by test coupon.3.3.7 Pmthe load carried by test coupo
29、n that is the lesserof the (1) maximum load before failure or (2) load at 5 % shearstrain.3.3.8 sn1standard deviation statistic of a sample popula-tion for a given property.3.3.9 xitest result for an individual coupon from thesample population for a given property.3.3.10 xmean or average (estimate o
30、f mean) of a samplepopulation for a given property.3.3.11 egeneral symbol for strain, whether normal strainor shear strain.3.3.12 eindicated normal strain from strain transducer orextensometer.3.3.13 t12shear stress on the plane perpendicular to the1-axis that acts parallel to the 2-axis.FIG. 1 Mate
31、rial Coordinate System FIG. 2 Definition of Specimen and Material AxesD 3518/D 3518M 94 (2007)23.3.14 t12mthe calculated value of the t12shear stresstaken at the lesser of (1) maximum shear stress before failureor (2) shear stress at 5 % shear strain.3.3.15 g12shear strain on the plane perpendicular
32、 to the1-axis that acts parallel to the 2-axis.3.3.16 g12mthe value of the g12shear strain at the maxi-mum shear stress before failure, or 5 %, whichever is less.4. Summary of Test Method4.1 A uniaxial tension test of a 645 laminate is performedin accordance with Test Method D 3039, although with sp
33、ecificrestrictions on stacking sequence and thickness. Use of this testfor evaluation of in-plane shear response was originally pro-posed by Petit3and was later improved by Rosen.4Usingexpressions derived from laminated plate theory, the in-planeshear stress in the material coordinate system is dire
34、ctlycalculated from the applied axial load, and the related shearstress is determined from longitudinal and transverse normalstrain data obtained by transducers. This data is used to createan in-plane shear stress-shear strain curve.5. Significance and Use5.1 This test method is designed to produce
35、in-plane shearproperty data for material specifications, research and devel-opment, quality assurance, and structural design and analysis.Factors that influence the shear response and should thereforebe reported include the following: material, methods of mate-rial preparation and lay-up, specimen s
36、tacking sequence andoverall thickness, specimen preparation, specimen condition-ing, environment of testing, specimen alignment and gripping,speed of testing, time at temperature, void content, and volumepercent reinforcement. Properties that may be derived from thistest method include the following
37、: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 shear properties,5.1.4 Maximum in-plane shear stress for a 645 laminate,and5.1.5 Maximum in-plane shear strain for a 645 laminate.6. Interferences6.1 Impurity of Stress FieldThe ma
38、terial in the gagesection of this specimen is not in a state of pure in-plane shearstress, as an in-plane normal stress component is presentthroughout the gage section and a complex stress field ispresent close to the free edges of the specimen. Although thistest method is believed to provide reliab
39、le initial materialresponse and can establish shear stress-shear strain responsewell into the nonlinear region, the calculated shear stressvalues at failure do not represent true material strength valuesand should only be used with caution. Despite attempts tominimize these effects, the shear stress
40、 at failure obtained fromthis test method, even for otherwise identical materials thatdiffer only in cured ply thickness or fabric areal weight, mayhave differing failure modes and may not be able to bestatistically pooled. The technical basis for the further discus-sion below is taken from the pape
41、r by Kellas et al.56.1.1 Effects of In-Plane Normal Stress FieldOf particularconcern is the in-plane stress component normal to the fiberdirection. This component of stress is present in all plies andthroughout the gage section of the specimen. The effect of thisstress on a given ply is minimized by
42、 the fiber reinforcement ofthe neighboring plies. Since the ply constraint is reduced withincreasing ply thickness, the thickness of the individual plies isan important parameter that influences both the shear stress-shear strain response and the ultimate failure load of thisspecimen.6Moreover, the
43、surface plies of a given specimen,being constrained by only one neighboring ply (as opposed tointerior plies, which are constrained by a ply on each side),represent the weakest link in a 645 specimen. During thetensile loading of this test coupon, the first ply failures consistprimarily of normal st
44、ress (or mixed mode) failures, rather thanpure shear failures. Because of this, the actual material shearstrength cannot be obtained from this test. Except for the caseof materials capable of sustaining large axial test couponstrains (greater than about 3.0 %), the shear stress at failure isbelieved
45、 to underestimate the actual material shear strength.6.1.2 Total Thickness EffectsAs a result of the failureprocesses discussed above, the shear stress-shear strain re-sponse at higher strain levels depends upon the total number ofplies. As the total number of plies in the specimen configura-tion is
46、 increased, the relative contribution of the two weaksurface plies to the total load-carrying capacity is decreased.After the surface plies of the laminate fail, their portion of theload is redistributed to the remainder of the intact plies. Thehigher the total number of plies, the greater the chanc
47、e that theremaining plies will be able to carry the load without imme-diate ultimate failure of the coupon. However, with eachsuccessive ply matrix failure the number of remaining intactplies diminishes, to the point where the applied load can nolonger be carried. Because of this process, higher ply
48、 countspecimens tend to achieve higher failure loads. To minimizethese effects, this test method requires the use of a homoge-neous stacking sequence and requires a fixed number of plies,for which the only repeating plies are the two required forsymmetry on opposite sides of the laminate mid plane.6
49、.1.3 Effects of Large DeformationNote that extreme fiberscissoring can occur in this specimen for the cases of ductilematrices, weak fiber/matrix interfaces, thick specimens with alarge number of repeated plies, or a combination of the above.Kellas et al suggest that a general rule of thumb for thisspecimen is that a fiber rotation of 1 takes place for every 2 %3Petit, D. H., “A Simplified Method of Determining the In-plane ShearStress/Strain Response of Unidirectional Composites,” Composite Materials: Test-ing and
