ASTM D3518/D3518M-94(2001)
(Test Method)Standard Test Method for In-Plane Shear Response of Polymer Matrix Composite Materials by Tensile Test of a ± 45o Laminate
Standard Test Method for In-Plane Shear Response of Polymer Matrix Composite Materials by Tensile Test of a ± 45<sup>o</sup> Laminate
SCOPE
1.1 This practice determines the in-plane shear response of polymer matrix composite materials reinforced by high-modulus fibers. The composite material form is limited to a continuous-fiber reinforced composite +45° laminate capable of being tension tested in the laminate chi-direction.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
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Designation: D 3518/D 3518M – 94 (Reapproved 2001)
Standard Test Method for
In-Plane Shear Response of Polymer Matrix Composite
Materials by Tensile Test of a 645° Laminate
This standard is issued under the fixed designation D3518/D3518M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. 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 Department of Defense.
1. Scope E111 TestMethodforYoung’sModulus,TangentModulus,
and Chord Modulus
1.1 This test method determines the in-plane shear response
E 177 Practice for Use of the Terms Precision and Bias in
of polymer matrix composite materials reinforced by high-
ASTM Test Methods
modulus fibers. The composite material form is limited to a
E 456 Terminology Relating to Quality and Statistics
continuous-fiber-reinforced composite 645° laminate capable
E 1309 Guide for Identification of Composite Materials in
of being tension tested in the laminate x direction.
Computerized Material Property Databases
1.2 This standard does not purport to address all of the
E 1313 Guide for Recommended Formats for Data Records
safety concerns, if any, associated with its use. It is the
Used In Computerization of Mechanical Test Data for
responsibility of the user of this standard to establish appro-
Metals
priate safety and health practices and determine the applica-
E 1434 Guide for Development of Standard Data Records
bility of regulatory limitations prior to use.
for Computerization of Mechanical Test Data for High-
1.3 The values stated in either SI units or inch-pound units
Modulus Fiber-Reinforced Composite Materials
are to be regarded separately as standard. Within the text the
E 1471 Guide for Identification of Fibers, Fillers, and Core
inch-pound units are shown in brackets. The values stated in
Materials in Computerized Material Property Databases
each system are not exact equivalents; therefore, each system
must be used independently of the other. Combining values
3. Terminology
from the two systems may result in nonconformance with the
3.1 Definitions—TerminologyD3878definestermsrelating
standard.
to high-modulus fibers and their composites. Terminology
2. Referenced Documents D883 defines terms relating to plastics. Terminology E6
defines terms relating to mechanical testing. Terminology
2.1 ASTM Standards:
2 E456 and Practice E177 define terms relating to statistics. In
D883 Terminology Relating to Plastics
the event of a conflict between terms, Terminology D3878
D3039/D3039M Test Method for Tensile Properties of
3 shall have precedence over the other standards.
Polymer Matrix Composite Materials
3.2 Definitions of Terms Specific to This Standard:
D3878 Terminology for High-Modulus Reinforcing Fibers
and Their Composites
NOTE 1—If the term represents a physical quantity, its analytical
D5229/D5229M Test Method for Moisutre Absorption dimensionsarestatedimmediatelyfollowingtheterm(orlettersymbol)in
fundamental dimension form, using the following ASTM standard sym-
Properties and Equilibrium Conditioning of Polymer Ma-
bology for fundamental dimensions, shown within square brackets: [M]
trix Composite Materials
formass,[L]forlength,[T]fortime,[Q]forthermodynamictemperature,
E 6 Terminology Relating to Methods of Mechanical Test-
and [nd] for nondimensional quantities. Use of these symbols is restricted
ing
to analytical dimensions when used with square brackets, as the symbols
may have other definitions when used without the brackets.
3.2.1 645° laminate—in laminated composites, a balanced,
This test method is under the jurisdiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.04 on
symmetric lay-up composed only of+45° plies and−45° plies.
Lamina and Laminate Test Methods.
(See also ply orientation.)
Current edition approved Nov. 15, 1994. Published January 1995. Originally
published as D3518–76. Last previous edition D3518–91.
Annual Book of ASTM Standards, Vol 08.01.
3 5
Annual Book of ASTM Standards, Vol 15.03. Annual Book of ASTM Standards, Vol 14.02.
4 6
Annual Book of ASTM Standards, Vol 03.01 Annual Book of ASTM Standards, Vol 14.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 3518/D 3518M
3.2.2 balanced, adj—in laminated composites, having, for axis of the principal material coordinate system with the
everyoff-axisplyorientedat+u,anotherplyorientedat−uthat direction of highest property value; for elastic properties, the
is of the same material system and form. axis of greatest elastic modulus is aligned with the 1 or x axes.
3.2.3 lamina, n—pl. laminae, in laminated composites,a 3.2.11 symmetric, adj—in laminated composites, when the
single, thin, uniform layer that is the basic building block of a constituents,materialform,andorientationfortheplieslocated
laminate. (Syn. ply). on one side of the laminate midplane are the mirror image of
3.2.4 material coordinate system, n—in laminated compos- the plies on the other side of the midplane.
ites,a123Cartesiancoordinatesystemdescribingtheprinciple 3.2.12 transition region, n—astrainregionofastress-strain
material coordinate system for a laminated material, where the or strain-strain curve over which a significant change in the
1-axis is aligned with the ply principal axis, as illustrated in slope of the curve occurs within a small strain range.
Fig. 1. (See also ply orientation, ply principal axis, and 3.2.12.1 Discussion—Many filamentary composite materi-
principal material coordinate system.) als exhibit a nonlinear stress/strain response during loading,
3.2.5 nominal value, n—a value, existing in name only, such as seen in plots of either longitudinal stress versus
assigned to a measurable property for the purpose of conve- longitudinal strain or transverse strain versus longitudinal
nient designation. Tolerances may be applied to a nominal strain. In certain cases, the nonlinear response may be conve-
value to define an acceptable range for the property. niently approximated by a bilinear fit. There are varying
3.2.6 off-axis, adj—in laminated composites, having a ply physical reasons for the existence of a transition region.
orientation that is neither 0 nor 90°. Common examples include matrix cracking under tensile
3.2.7 ply, n—in laminated composites,synonymfor lamina. loading and ply delamination.
3.2.8 ply orientation, n, u—in laminated composites, the 3.3 Symbols:
angle between a reference direction and the ply principal axis. 3.3.1 A—cross-sectional area of a coupon.
The angle is expressed in degrees, greater than−90° but less 3.3.2 CV—coefficient of variation statistic of a sample
thanorequalto+90°,andisshownasapositivequantitywhen population for a given property (in percent).
taken from the reference direction to the ply principal axis, 3.3.3 F ° (offset)—the value of the t shear stress at the
12 12
following the right-hand rule. intersection of the shear chord modulus of elasticity and the
3.2.8.1 Discussion—The reference direction is usually re- stress stress curve, when the modulus is offset along the shear
lated to a primary load-carrying direction. strain axis from the origin by the reported strain offset value.
3.2.9 ply principal axis, n—in laminated composites, the 3.3.4 G —in-plane shear modulus of elasticity.
coordinate axis in the plane of each lamina that defines the ply 3.3.4.1 Discussion—Indices1and2indicatethefiberdirec-
orientation. (See also ply orientation and material coordinate tionandtransversetothefiberdirectionintheplaneoftheply,
system.) respectively, as illustrated in Fig. 2.
3.2.9.1 Discussion—The ply principal axis will, in general, 3.3.5 n—number of coupons per sample population.
be different for each ply of a laminate. The angle that this axis 3.3.6 P—load carried by test coupon.
m
makes relative to a reference axis is given by the ply orienta- 3.3.7 P —the load carried by test coupon that is the lesser
tion. The convention is to align the ply principal axis with the ofthe(1)maximumloadbeforefailureor(2)loadat5%shear
direction of maximum stiffness (for example, the fiber direc- strain.
tion of unidirectional tape or the warp direction of fabric 3.3.8 s —standard deviation statistic of a sample popula-
n−1
reinforced material). tion for a given property.
3.2.10 principal material coordinate system, n—a coordi-
natesystemhavingaxesthatarenormaltoplanesofsymmetry
within the material. (See also material coordinate system.)
3.2.10.1 Discussion—Common usage, at least for Cartesian
coordinate systems (for example, 123 or xyz), aligns the first
FIG. 1 Material Coordinate System FIG. 2 Definition of Specimen and Material Axes
D 3518/D 3518M
3.3.9 x—test result for an individual coupon from the 6. Interferences
i
sample population for a given property.
6.1 Impurity of Stress Field—The material in the gage
3.3.10 x¯—mean or average (estimate of mean) of a sample
section of this specimen is not in a state of pure in-plane shear
population for a given property.
stress, as an in-plane normal stress component is present
3.3.11 e—general symbol for strain, whether normal strain
throughout the gage section and a complex stress field is
or shear strain.
present close to the free edges of the specimen. Although this
3.3.12 e—indicated normal strain from strain transducer or
test method is believed to provide reliable initial material
extensometer.
response and can establish shear stress-shear strain response
3.3.13 t —shear stress on the plane perpendicular to the well into the nonlinear region, the calculated shear stress
1-axis that acts parallel to the 2-axis.
values at failure do not represent true material strength values
m
3.3.14 t —the calculated value of the t shear stress and should only be used with caution. Despite attempts to
12 12
taken at the lesser of (1) maximum shear stress before failure minimizetheseeffects,theshearstressatfailureobtainedfrom
or (2) shear stress at 5% shear strain. this test method, even for otherwise identical materials that
3.3.15 g —shear strain on the plane perpendicular to the differ only in cured ply thickness or fabric areal weight, may
have differing failure modes and may not be able to be
1-axis that acts parallel to the 2-axis.
m
statistically pooled. The technical basis for the further discus-
3.3.16 g —the value of the g shear strain at the maxi-
12 12
sion below is taken from the paper by Kellas et al.
mum shear stress before failure, or 5%, whichever is less.
6.1.1 EffectsofIn-PlaneNormalStressField—Ofparticular
concern is the in-plane stress component normal to the fiber
4. Summary of Test Method
direction. This component of stress is present in all plies and
4.1 Auniaxial tension test of a 645° laminate is performed
throughout the gage section of the specimen.The effect of this
inaccordancewithTestMethodD3039,althoughwithspecific
stressonagivenplyisminimizedbythefiberreinforcementof
restrictionsonstackingsequenceandthickness.Useofthistest
the neighboring plies. Since the ply constraint is reduced with
for evaluation of in-plane shear response was originally pro-
increasingplythickness,thethicknessoftheindividualpliesis
7 8
posed by Petit and was later improved by Rosen. Using
an important parameter that influences both the shear stress-
expressions derived from laminated plate theory, the in-plane
shear strain response and the ultimate failure load of this
shear stress in the material coordinate system is directly
specimen. Moreover, the surface plies of a given specimen,
calculated from the applied axial load, and the related shear
being constrained by only one neighboring ply (as opposed to
stress is determined from longitudinal and transverse normal
interior plies, which are constrained by a ply on each side),
strain data obtained by transducers. This data is used to create
represent the weakest link in a 645° specimen. During the
an in-plane shear stress-shear strain curve.
tensile loading of this test coupon, the first ply failures consist
primarilyofnormalstress(ormixedmode)failures,ratherthan
5. Significance and Use
pure shear failures. Because of this, the actual material shear
5.1 This test method is designed to produce in-plane shear
strength cannot be obtained from this test. Except for the case
property data for material specifications, research and devel-
of materials capable of sustaining large axial test coupon
opment, quality assurance, and structural design and analysis.
strains (greater than about 3.0%), the shear stress at failure is
Factors that influence the shear response and should therefore
believed to underestimate the actual material shear strength.
be reported include the following: material, methods of mate-
6.1.2 Total Thickness Effects—As a result of the failure
rial preparation and lay-up, specimen stacking sequence and
processes discussed above, the shear stress-shear strain re-
overall thickness, specimen preparation, specimen condition-
sponseathigherstrainlevelsdependsuponthetotalnumberof
ing, environment of testing, specimen alignment and gripping,
plies. As the total number of plies in the specimen configura-
speedoftesting,timeattemperature,voidcontent,andvolume
tion is increased, the relative contribution of the two weak
percentreinforcement.Propertiesthatmaybederivedfromthis
surface plies to the total load-carrying capacity is decreased.
test method include the following:
After the surface plies of the laminate fail, their portion of the
5.1.1 In-plane shear stress versus shear strain response,
load is redistributed to the remainder of the intact plies. The
5.1.2 In-plane shear chord modulus of elasticity,
higher the total number of plies, the greater the chance that the
remaining plies will be able to carry the load without imme-
5.1.3 Offset shear properties,
diate ultimate failure of the coupon. However, with each
5.1.4 Maximum in-plane shear stress for a 645° laminate,
successive ply matrix failure the number of remaining intact
and
plies diminishes, to the point where the applied load can no
5.1.5 Maximum in-plane shear strain for a 645° laminate.
longer be carried. Because of this process, higher ply count
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Petit, D. H., “A Simplified Method of Determining the In-plane Shear Kellas,S.,Morton,J.,andJackson,K.E.,“DamageandFailureMechanismsin
Stress/Strain Response of Unidirectional Composites,” Composite Materials: Test- Scaled Angled-Ply Laminates,” Fourth Composites Symposium on Fatigue and
ing and Design, ASTM STP 460,American Societ
...
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