ASTM D7137/D7137M-05
(Test Method)Standard Test Method for Compressive Residual Strength Properties of Damaged Polymer Matrix Composite Plates
Standard Test Method for Compressive Residual Strength Properties of Damaged Polymer Matrix Composite Plates
SCOPE
1.1 This test method covers compression residual strength properties of multidirectional polymer matrix composite laminated plates, which have been subjected to quasi-static indentation per Test Method D 6264 or drop-weight impact per Test Method D 7136/D 7136M prior to application of compressive force. The composite material forms are limited to continuous-fiber reinforced polymer matrix composites with multidirectional fiber orientations, and which are both symmetric and balanced with respect to the test direction. The range of acceptable test laminates and thicknesses is defined in .Note 1
When used to determine the residual strength of drop-weight impacted plates, this test method is commonly referred to as the Compression After Impact, or CAI, method.
1.2 The method utilizes a flat, rectangular composite plate, previously subjected to a damaging event, which is tested under compressive loading using a stabilization fixture.Note 2
The damage tolerance properties obtained are particular to the type, geometry and location of damage inflicted upon the plate.
1.3 The properties generated by this test method are highly dependent upon several factors, which include specimen geometry, layup, damage type, damage size, damage location, and boundary conditions. Thus, results are generally not scalable to other configurations, and are particular to the combination of geometric and physical conditions tested.
1.4 This test method can be used to test undamaged polymer matrix composite plates, but historically such tests have demonstrated a relatively high incidence of undesirable failure modes (such as end crushing). Test Method D 6641/D 6641M is recommended for obtaining compressive properties of undamaged polymer matrix composites.
1.5 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.
1.6 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.
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Designation:D7137/D7137M–05
Standard Test Method for
Compressive Residual Strength Properties of Damaged
Polymer Matrix Composite Plates
This standard is issued under the fixed designation D 7137/D 7137M; 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.
1. Scope must be used independently of the other. Combining values
from the two systems may result in nonconformance with the
1.1 This test method covers compression residual strength
standard.
properties of multidirectional polymer matrix composite lami-
1.6 This standard does not purport to address all of the
nated plates, which have been subjected to quasi-static inden-
safety concerns, if any, associated with its use. It is the
tation per Test Method D 6264 or drop-weight impact per Test
responsibility of the user of this standard to establish appro-
Method D 7136/D 7136M prior to application of compressive
priate safety and health practices and determine the applica-
force. The composite material forms are limited to continuous-
bility of regulatory limitations prior to use.
fiber reinforced polymer matrix composites with multidirec-
tional fiber orientations, and which are both symmetric and
2. Referenced Documents
balanced with respect to the test direction. The range of
2.1 ASTM Standards:
acceptable test laminates and thicknesses is defined in 8.2.
D 792 TestMethodsforDensityandSpecificGravity(Rela-
NOTE 1—When used to determine the residual strength of drop-weight
tive Density) of Plastics by Displacement
impacted plates, this test method is commonly referred to as the
D 883 Terminology Relating to Plastics
Compression After Impact, or CAI, method.
D 3171 Test Methods for Constituent Content of Composite
1.2 The method utilizes a flat, rectangular composite plate,
Materials
previously subjected to a damaging event, which is tested
D 3878 Terminology for Composite Materials
under compressive loading using a stabilization fixture.
D 5229/D 5229M Test Method for Moisture Absorption
Properties and Equilibrium Conditioning of Polymer Ma-
NOTE 2—Thedamagetolerancepropertiesobtainedareparticulartothe
trix Composite Laminates
type, geometry and location of damage inflicted upon the plate.
D 5687/D 5687M Guide for Preparation of Flat Composite
1.3 The properties generated by this test method are highly
Panels with Processing Guidelines for Specimen Prepara-
dependent upon several factors, which include specimen ge-
tion
ometry, layup, damage type, damage size, damage location,
D 6264 Test Method for Measuring the Damage Resistance
and boundary conditions. Thus, results are generally not
of a Fiber-Reinforced Polymer-Matrix Composite to a
scalable to other configurations, and are particular to the
Concentrated Quasi-Static Indentation Force
combination of geometric and physical conditions tested.
D 6641/D 6641M Test Method for Determining the Com-
1.4 Thistestmethodcanbeusedtotestundamagedpolymer
pressive Properties of Polymer Matrix Composite Lami-
matrix composite plates, but historically such tests have
natesUsingaCombinedLoadingCompression(CLC)Test
demonstrated a relatively high incidence of undesirable failure
Fixture
modes (such as end crushing). Test Method D 6641/D 6641M
D 7136/D 7136M Test Method for Measuring the Damage
is recommended for obtaining compressive properties of un-
Resistance of a Fiber-Reinforced Polymer Matrix Com-
damaged polymer matrix composites.
posite to a Drop-Weight Impact Event
1.5 The values stated in either SI units or inch-pound units
E4 Practices for Force Verification of Testing Machines
are to be regarded separately as standard. Within the text the
E6 Terminology Relating to Methods of Mechanical Test-
inch-pound units are shown in brackets. The values stated in
ing
each system are not exact equivalents; therefore, each system
1 2
This test method is under the jurisdiction of ASTM Committee D30 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Composite Materials and is the direct responsibility of Subcommittee D30.05 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Structural Test Methods. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved April 1, 2005. Published April 2005. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7137/D7137M–05
E 122 Practice for Calculation of Sample Size to Estimate, 3.2.2 principal material coordinate system, n—a coordinate
with a Secified Tolerable Error, the Average of Character- system with axes that are normal to the planes of symmetry
istic for a Lot or Process inherent to a material.
E 177 Practice for Use of the Terms Precision and Bias in 3.2.2.1 Discussion—Common usage, at least for Cartesian
ASTM Test Methods axes (123, xyz, and so forth), generally assigns the coordinate
E 456 Terminology Relating to Quality and Statistics system axes to the normal directions of planes of symmetry in
E 1309 Guide for Identification of Fiber-Reinforced Poly- order that the highest property value in a normal direction (for
mer Matrix Composite Materials in Databases elastic properties, the axis of greatest stiffness) would be 1 or
E 1434 GuideforRecordingMechanicalTestDataofFiber- x, and the lowest (if applicable) would be 3 or z. Anisotropic
Reinforced Composite Materials in Databases materials do not have a principal material coordinate system
E 1471 Guide for Identification of Fibers, Fillers and Core duetothetotallackofsymmetry,while,forisotropicmaterials,
Materials in Computerized Material Property Databases any coordinate system is a principal material coordinate
2.2 Military Standards: system. In laminated composites, the principal material coor-
MIL-HDBK-17-3F Composite Materials Handbook, Vol- dinate system has meaning only with respect to an individual
ume 3—Polymer Matrix Composites Materials Usage, orthotropic lamina. The related term for laminated composites
Design and Analysis
is “reference coordinate system.”
MIL-HDBK-728/1 Nondestructive Testing 3.2.3 reference coordinate system, n—a coordinate system
MIL-HDBK-731A Nondestructive Testing Methods of
for laminated composites used to define ply orientations. One
Composite Materials—Thermography of the reference coordinate system axes (normally the Carte-
MIL-HDBK-732A Nondestructive Testing Methods of
sian x-axis) is designated the reference axis, assigned a
Composite Materials—Acoustic Emission position, and the ply principal axis of each ply in the laminate
MIL-HDBK-733A Nondestructive Testing Methods of
is referenced relative to the reference axis to define the ply
Composite Materials—Radiography orientation for that ply.
MIL-HDBK-787A Nondestructive Testing Methods of
3.2.4 specially orthotropic, adj—a description of an ortho-
Composite Materials—Ultrasonics tropic material as viewed in its principal material coordinate
NASA Reference Publication 1092 Standard Tests for
system. In laminated composites, a specially orthotropic lami-
Toughened Resin Composites, Revised Edition, July nate is a balanced and symmetric laminate of the [0/90]
i j ns
1983 family as viewed from the reference coordinate system, such
that the membrane-bending coupling terms of the laminate
3. Terminology
constitutive relation are zero.
3.1 Definitions—TerminologyD 3878definestermsrelating 3.3 Symbols:
to composite materials. Terminology D 883 defines terms
A = cross-sectional area of a specimen
relating to plastics. TerminologyE6 defines terms relating to CV = coefficient of variation statistic of a sample population
mechanical testing. Terminology E 456 and Practice E 177
for a given property (in percent)
define terms relating to statistics. In the event of a conflict D = damage diameter (see Fig. 13).
CAI
between terms, Terminology D 3878 shall have precedence
E = effective compressive modulus in the test direction
CAI
over the other standards. F = ultimate compressive residual strength in the test
3.2 Definitions of Terms Specific to This Standard—If the
direction
term represents a physical quantity, its analytical dimensions h = specimen thickness
are stated immediately following the term (or letter symbol) in
l = specimen length
fundamental dimension form, using the following ASTM
n = number of specimens per sample population
standard symbology for fundamental dimensions, shown
N = number of plies in laminate under test
within square brackets: [M] for mass, [L] for length, [T] for
P = maximum force carried by test specimen prior to
max
time, [u] for thermodynamic temperature, and [nd] for non-
failure
dimensional quantities. Use of these symbols is restricted to
S = standard deviation statistic of a sample population for
n-1
analytical dimensions when used with square brackets, as the
a given property
symbols may have other definitions when used without the
w = specimen width
brackets.
x = test result for an individual specimen from the sample
i
3.2.1 nominal value, n—a value, existing in name only,
population for a given property
assigned to a measurable property for the purpose of conve-
–
x = mean or average (estimate of mean) of a sample popu-
nient designation. Tolerances may be applied to a nominal
lation for a given property
value to define an acceptable range for the property.
4. Summary of Test Method
4.1 A uniaxial compression test is performed using a bal-
Available from U.S. Army Research Laboratory, Materials Directorate, Aber-
deen Proving Ground, MD 21001.
anced, symmetric laminated plate, which has been damaged
Available from U.S. Army Materials Technology Laboratory, Watertown, MA
and inspected prior to the application of compressive force.
02471.
The damage state is imparted through out-of-plane loading
Available from National Aeronautics and Space Administration (NASA)-
Langley Research Center, Hampton, VA 23681-2199. caused by quasi-static indentation or drop-weight impact.
D7137/D7137M–05
FIG. 1 Schematic of Compressive Residual Strength Support Fixture with Specimen in Place
FIG. 2 Support Fixture Assembly
D7137/D7137M–05
FIG. 3 Support Fixture Base Plate (Inch-Pound Version)
FIG. 4 Support Fixture Base Plate (SI Version)
4.1.1 Quasi-Static Indentation—The rectangular plate is sive force until failure.Applied force, crosshead displacement,
damaged due to application of an out-of-plane static indenta- and strain data are recorded while loading.
tion force in accordance with Test Method D 6264.
4.3 Preferred failure modes pass through the damage in the
4.1.2 Drop-Weight Impact—The rectangular plate is dam-
test specimen. However, acceptable failures may initiate away
aged due to application of an out-of-plane drop-weight impact
from the damage site, in instances when the damage produces
in accordance with Test Method D 7136/D 7136M.
a relatively low stress concentration or if the extent of damage
4.1.3 Damage Assessment—If not previously determined
is small, or both. Unacceptable failure modes are those related
after the damaging event, the extent of damage is determined
to load introduction by the support fixture, local edge support
using non-destructive inspection (NDI) procedures as de-
conditions, and specimen instability (unless the specimen is
scribed in 11.4.
dimensionally representative of a particular structural applica-
4.2 The damaged plate is installed in a multi-piece support
tion).
fixture,thathasbeenalignedtominimizeloadingeccentricities
andinducedspecimenbending.Thespecimen/fixtureassembly
is placed between flat platens and end-loaded under compres-
D7137/D7137M–05
FIG. 5 Support Fixture Angles (Inch-Pound Version)
5. Significance and Use more likely reflect the damage tolerance characteristics of an
un-stiffened monolithic skin or web than that of a skin attached
5.1 Susceptibilitytodamagefromconcentratedout-of-plane
to substructure which resists out-of-plane deformation. Simi-
forces is one of the major design concerns of structures made
larly, test specimen properties would be expected to be similar
of advanced composite laminates. Knowledge of the damage
to those of a panel with equivalent length and width dimen-
resistance and damage tolerance properties of a laminated
sions, in comparison to those of a panel significantly larger
composite plate is useful for product development and material
than the test specimen.
selection.
5.2 The residual strength data obtained using this test 5.4 The reporting section requires items that tend to influ-
method is most commonly used in material specifications and
ence residual compressive strength to be reported; these
research and development activities. The data are not intended
include the following: material, methods of material fabrica-
for use in establishing design allowables, as the results are
tion, accuracy of lay-up orientation, laminate stacking se-
specific to the geometry and physical conditions tested and are
quence and overall thickness, specimen geometry, specimen
generally not scalable to other configurations. Its usefulness in
preparation, specimen conditioning, environment of testing,
establishing quality assurance requirements is also limited, due
void content, volume percent reinforcement, type, size and
to the inherent variability of induced damage, as well as the
location of damage (including method of non-destructive
dependency of damage tolerance response upon the pre-
inspection), specimen/fixture alignment and gripping, and
existent damage state.
speed of testing.
5.3 The properties obtained using this test method can
5.5 Properties that result from the residual strength assess-
provide guidance in regard to the anticipated damage tolerance
ment include the following: compressive residual strength
capability of composite structures of similar material, thick-
CAI
F , compressive force as a function of crosshead displace-
ness, stacking sequence, and so forth. However, it must be
ment, and surface strains as functions of crosshead displace-
understood that the damage tolerance of a composite structure
ment.
is highly dependent upon several factors including geometry,
stiffness, support conditions, and so forth. Significant differ-
6. Interferences
ences in the relationships between the existent damage state
and the residual compressive strength can result due to 6.1 The response of a damaged specimen is dependent upon
many factors,
...
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