ASTM D3518/D3518M-94(2007)
(Test Method)Standard Test Method for In-Plane Shear Response of Polymer Matrix Composite Materials by Tensile Test of a ±45° Laminate
Standard Test Method for In-Plane Shear Response of Polymer Matrix Composite Materials by Tensile Test of a ±45° Laminate
SIGNIFICANCE AND USE
This test method is designed to produce in-plane shear property data for material specifications, research and development, quality assurance, and structural design and analysis. Factors that influence the shear response and should therefore be reported include the following: material, methods of material preparation and lay-up, specimen stacking sequence and overall thickness, specimen preparation, specimen conditioning, environment of testing, specimen alignment and gripping, speed of testing, time at temperature, void content, and volume percent reinforcement. Properties that may be derived from this test method include the following:
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 ±45° laminate, and
5.1.5 Maximum in-plane shear strain for a ±45° laminate.
SCOPE
1.1 This test method 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 direction.
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.
1.2 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D3518/D3518M − 94(Reapproved 2007)
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 (´) 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 E177Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
1.1 This test method determines the in-plane shear response
E456Terminology Relating to Quality and Statistics
of polymer matrix composite materials reinforced by high-
E1309 Guide for Identification of Fiber-Reinforced
modulus fibers. The composite material form is limited to a
Polymer-Matrix Composite Materials in Databases
continuous-fiber-reinforced composite 645° laminate capable
E1434Guide for Recording Mechanical Test Data of Fiber-
of being tension tested in the laminate χ direction.
Reinforced Composite Materials in Databases
1.2 This standard does not purport to address all of the
E1471Guide for Identification of Fibers, Fillers, and Core
safety concerns, if any, associated with its use. It is the
Materials in Computerized Material Property Databases
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
3. Terminology
bility of regulatory limitations prior to use.
3.1 Definitions—Terminology D3878 defines terms relating
1.3 The values stated in either SI units or inch-pound units
to high-modulus fibers and their composites. Terminology
are to be regarded separately as standard. Within the text the
D883definestermsrelatingtoplastics.TerminologyE6defines
inch-pound units are shown in brackets. The values stated in
terms relating to mechanical testing. Terminology E456 and
each system are not exact equivalents; therefore, each system
Practice E177 define terms relating to statistics. In the event of
must be used independently of the other. Combining values
a conflict between terms, Terminology D3878 shall have
from the two systems may result in nonconformance with the
precedence over the other standards.
standard.
3.2 Definitions of Terms Specific to This Standard:
2. Referenced Documents
NOTE 1—If the term represents a physical quantity, its analytical
2 dimensionsarestatedimmediatelyfollowingtheterm(orlettersymbol)in
2.1 ASTM Standards:
fundamental dimension form, using the following ASTM standard sym-
D883Terminology Relating to Plastics
bology for fundamental dimensions, shown within square brackets: [M]
D3039/D3039MTestMethodforTensilePropertiesofPoly-
formass,[L]forlength,[T]fortime,[Θ]forthermodynamictemperature,
and[nd]fornondimensionalquantities.Useofthesesymbolsisrestricted
mer Matrix Composite Materials
to analytical dimensions when used with square brackets, as the symbols
D3878Terminology for Composite Materials
may have other definitions when used without the brackets.
D5229/D5229MTestMethodforMoistureAbsorptionProp-
3.2.1 645° laminate—in laminated composites, a balanced,
erties and Equilibrium Conditioning of Polymer Matrix
symmetric lay-up composed only of+45° plies and−45° plies.
Composite Materials
(See also ply orientation.)
E6Terminology Relating to Methods of MechanicalTesting
3.2.2 balanced, adj—in laminated composites, having, for
E111Test Method for Young’s Modulus, Tangent Modulus,
everyoff-axisplyorientedat+θ,anotherplyorientedat−θthat
and Chord Modulus
is of the same material system and form.
3.2.3 lamina, n—pl. laminae, in laminated composites,a
This test method is under the jurisdiction of ASTM Committee D30 on
single, thin, uniform layer that is the basic building block of a
Composite Materials and is the direct responsibility of Subcommittee D30.04 on
laminate. (Syn. ply ).
Lamina and Laminate Test Methods.
3.2.4 material coordinate system, n—in laminated
Current edition approved May 1, 2007. Published June 2007. Originally
composites, a 123 Cartesian coordinate system describing the
approved in 1976. Last previous edition approved in 2001 as D3518/
D3518M–94(2001). DOI: 10.1520/D3518_D3518M-94R07.
principle material coordinate system for a laminated material,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
where the 1-axis is aligned with the ply principal axis, as
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
illustrated in Fig. 1. (See also ply orientation, ply principal
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. axis, and principal material coordinate system.)
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3518/D3518M − 94 (2007)
such as seen in plots of either longitudinal stress versus
longitudinal strain or transverse strain versus longitudinal
strain. In certain cases, the nonlinear response may be conve-
niently approximated by a bilinear fit. There are varying
physical reasons for the existence of a transition region.
Common examples include matrix cracking under tensile
loading and ply delamination.
3.3 Symbols:
3.3.1 A—cross-sectional area of a coupon.
3.3.2 CV—coefficient of variation statistic of a sample
population for a given property (in percent).
3.3.3 F ° (offset)—the value of the τ shear stress at the
12 12
intersection of the shear chord modulus of elasticity and the
FIG. 1 Material Coordinate System
stress stress curve, when the modulus is offset along the shear
strain axis from the origin by the reported strain offset value.
3.2.5 nominal value, n—a value, existing in name only,
3.3.4 G —in-plane shear modulus of elasticity.
assigned to a measurable property for the purpose of conve-
3.3.4.1 Discussion—Indices 1 and 2 indicate the fiber direc-
nient designation. Tolerances may be applied to a nominal
tionandtransversetothefiberdirectionintheplaneoftheply,
value to define an acceptable range for the property.
respectively, as illustrated in Fig. 2.
3.2.6 off-axis, adj—in laminated composites, having a ply
3.3.5 n—number of coupons per sample population.
orientation that is neither 0 nor 90°.
3.3.6 P—load carried by test coupon.
3.2.7 ply, n—in laminated composites, synonym for lamina.
m
3.2.8 ply orientation, n, θ—in laminated composites, the
3.3.7 P —the load carried by test coupon that is the lesser
angle between a reference direction and the ply principal axis.
ofthe(1)maximumloadbeforefailureor(2)loadat5%shear
The angle is expressed in degrees, greater than−90° but less
strain.
thanorequalto+90°,andisshownasapositivequantitywhen
3.3.8 s —standard deviation statistic of a sample popula-
n−1
taken from the reference direction to the ply principal axis,
tion for a given property.
following the right-hand rule.
3.3.9 χ—test result for an individual coupon from the
i
3.2.8.1 Discussion—The reference direction is usually re-
sample population for a given property.
lated to a primary load-carrying direction.
3.3.10 χ¯—mean or average (estimate of mean) of a sample
3.2.9 ply principal axis, n—in laminated composites, the
population for a given property.
coordinate axis in the plane of each lamina that defines the ply
orientation. (See also ply orientation and material coordinate
3.3.11 ´—general symbol for strain, whether normal strain
system.)
or shear strain.
3.2.9.1 Discussion—The ply principal axis will, in general,
3.3.12 ´—indicated normal strain from strain transducer or
be different for each ply of a laminate. The angle that this axis
extensometer.
makes relative to a reference axis is given by the ply orienta-
tion. The convention is to align the ply principal axis with the
direction of maximum stiffness (for example, the fiber direc-
tion of unidirectional tape or the warp direction of fabric
reinforced material).
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
axis of the principal material coordinate system with the
direction of highest property value; for elastic properties, the
axis of greatest elastic modulus is aligned with the 1 or x axes.
3.2.11 symmetric, adj—in laminated composites, when the
constituents,materialform,andorientationfortheplieslocated
on one side of the laminate midplane are the mirror image of
the plies on the other side of the midplane.
3.2.12 transition region, n—a strain region of a stress-strain
or strain-strain curve over which a significant change in the
slope of the curve occurs within a small strain range.
3.2.12.1 Discussion—Many filamentary composite materi-
als exhibit a nonlinear stress/strain response during loading, FIG. 2 Definition of Specimen and Material Axes
D3518/D3518M − 94 (2007)
3.3.13 τ —shear stress on the plane perpendicular to the response and can establish shear stress-shear strain response
1-axis that acts parallel to the 2-axis. well into the nonlinear region, the calculated shear stress
m
values at failure do not represent true material strength values
3.3.14 τ —the calculated value of the τ shear stress
12 12
and should only be used with caution. Despite attempts to
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 γ —shear strain on the plane perpendicular to the
differ only in cured ply thickness or fabric areal weight, may
1-axis that acts parallel to the 2-axis.
have differing failure modes and may not be able to be
m
3.3.16 γ —the value of the γ shear strain at the maxi-
12 12 statistically pooled. The technical basis for the further discus-
mum shear stress before failure, or 5%, whichever is less.
sion below is taken from the paper by Kellas et al.
6.1.1 Effects of In-Plane Normal Stress Field—Ofparticular
4. Summary of Test Method
concern is the in-plane stress component normal to the fiber
4.1 Auniaxial tension test of a 645° laminate is performed direction. This component of stress is present in all plies and
in accordance with Test Method D3039/D3039M, although
throughout the gage section of the specimen.The effect of this
with specific restrictions on stacking sequence and thickness. stressonagivenplyisminimizedbythefiberreinforcementof
Use of this test for evaluation of in-plane shear response was the neighboring plies. Since the ply constraint is reduced with
originally proposed by Petit and was later improved by increasingplythickness,thethicknessoftheindividualpliesis
Rosen. Using expressions derived from laminated plate an important parameter that influences both the shear stress-
theory, the in-plane shear stress in the material coordinate shear strain response and the ultimate failure load of this
system is directly calculated from the applied axial load, and specimen. Moreover, the surface plies of a given specimen,
the related shear stress is determined from longitudinal and being constrained by only one neighboring ply (as opposed to
transverse normal strain data obtained by transducers. This interior plies, which are constrained by a ply on each side),
data is used to create an in-plane shear stress-shear strain
represent the weakest link in a 645° specimen. During the
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
strength cannot be obtained from this test. Except for the case
5.1 This test method is designed to produce in-plane shear
of materials capable of sustaining large axial test coupon
property data for material specifications, research and
strains (greater than about 3.0%), the shear stress at failure is
development, quality assurance, and structural design and
believed to underestimate the actual material shear strength.
analysis. Factors that influence the shear response and should
6.1.2 Total Thickness Effects—As a result of the failure
therefore be reported include the following: material, methods
processes discussed above, the shear stress-shear strain re-
of material preparation and lay-up, specimen stacking se-
sponseathigherstrainlevelsdependsuponthetotalnumberof
quence and overall thickness, specimen preparation, specimen
plies. As the total number of plies in the specimen configura-
conditioning, environment of testing, specimen alignment and
tion is increased, the relative contribution of the two weak
gripping, speed of testing, time at temperature, void content,
surface plies to the total load-carrying capacity is decreased.
and volume percent reinforcement. Properties that may be
After the surface plies of the laminate fail, their portion of the
derived from this test method include the following:
load is redistributed to the remainder of the intact plies. The
5.1.1 In-plane shear stress versus shear strain response,
higher the total number of plies, the greater the chance that the
5.1.2 In-plane shear chord modulus of elasticity,
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
6. Interferences specimens tend to achieve higher failure loads. To minimize
these effects, this test method requires the use of a homoge-
6.1 Impurity of Stress Field—The material in the gage
neous stacking sequence and requires a fixed number of plies,
section of this specimen is not in a state of pure in-plane shear
for which the only repeating plies are the two required for
stress, as an in-plane normal stress component is present
symmetry on opposite sides of the laminate mid plane.
throughout the gage section and a complex stress field is
6.1.3 EffectsofLargeDeformation—Notethatextremefiber
present close to the free edges of the specimen. Although this
scissoring can occur in this specimen for the cases of ductile
test method is believed to provide reliable initial material
3 5
Petit, D. H.,
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.