ASTM D7137/D7137M-23

Standard Test Method for Compressive Residual Strength Properties of Damaged Polymer Matrix Composite Plates

SIGNIFICANCE AND USE
5.1 Susceptibility to damage from concentrated out-of-plane forces is one of the major design concerns of many structures made of advanced composite laminates. Knowledge of the damage resistance and damage tolerance properties of a laminated composite plate is useful for product development and material selection.  
5.2 The residual strength data obtained using this test method is most commonly used in material specifications and research and development activities. The data are not intended for use in establishing design allowables, as the results are specific to the geometry and physical conditions tested and are generally not scalable to other configurations. Its usefulness in establishing quality assurance requirements is also limited, due to the inherent variability of induced damage, as well as the dependency of damage tolerance response upon the pre-existent damage state.  
5.3 The properties obtained using this test method can provide guidance in regard to the anticipated damage tolerance capability of composite structures of similar material, thickness, stacking sequence, and so forth. However, it must be understood that the damage tolerance of a composite structure is highly dependent upon several factors including geometry, stiffness, support conditions, and so forth. Significant differences in the relationships between the existent damage state and the residual compressive strength can result due to differences in these parameters. For example, residual strength and stiffness properties obtained using this test method would more likely reflect the damage tolerance characteristics of an un-stiffened monolithic skin or web than that of a skin attached to substructure which resists out-of-plane deformation. Similarly, test specimen properties would be expected to be similar to those of a panel with equivalent length and width dimensions, in comparison to those of a panel significantly larger than the test specimen.  
5.4 The reporting section requires it...
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 D6264/D6264M or drop-weight impact per Test Method D7136/D7136M 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 8.2.
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 D6641/D6641M is recommended for obtaining compressive properties of undamaged polymer matrix composites.  
1.5 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equiv...

General Information

• Status: Published
• Publication Date: 30-Apr-2023
• ICS: 83.120 - Reinforced plastics
• Technical Committee: D30 - Composite Materials
• Drafting Committee: D30.05 - Structural Test Methods

Relations

• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D6641/D6641M-23 - Standard Test Method for Compressive Properties of Polymer Matrix Composite Materials Using a Combined Loading Compression (CLC) Test Fixture
• Effective Date: 15-Nov-2023
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM D5229/D5229M-20 - Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials
• Effective Date: 01-Mar-2020
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM D3878-19a - Standard Terminology for Composite Materials
• Effective Date: 15-Oct-2019
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D3878-19 - Standard Terminology for Composite Materials
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM D3878-18 - Standard Terminology for Composite Materials
• Effective Date: 01-Apr-2018
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017

Overview

ASTM D7137/D7137M-23 is the internationally recognized standard test method for determining the compressive residual strength properties of damaged polymer matrix composite plates. Issued by ASTM International, this method is essential for evaluating the compression after impact (CAI) properties of advanced multidirectional, continuous-fiber reinforced polymer matrix composites after they have sustained damage, such as from quasi-static indentation or drop-weight impact.

The principal objective of ASTM D7137/D7137M-23 is to provide a uniform, repeatable procedure for assessing the loss in compressive strength after a composite laminate is damaged. This information supports material selection, product development, and research, though results are generally not intended for deriving design allowables due to influences from specific test conditions.

Key Topics

• Compression After Impact (CAI): This standard focuses on quantifying the residual compressive strength of composite plates after they have been damaged through impact or indentation.
• Test Specimen Requirements: Applies to flat, rectangular, continuous fiber-reinforced polymer matrix composite laminates with balanced and symmetric multidirectional layups.
• Damage Induction: Plates are pre-damaged according to ASTM D6264/D6264M (quasi-static indentation) or ASTM D7136/D7136M (drop-weight impact) before compressive testing.
• Specialized Fixtures: Utilizes a specific stabilization support fixture to minimize buckling and ensure uniform compressive loading during testing.
• Result Dependence: The residual strength obtained is highly sensitive to the test specimen's geometry, stacking sequence, damage characteristics, and boundary conditions.
• Reporting Requirements: Comprehensive documentation is required regarding specimen preparation, test conditions, and damage parameters to ensure data consistency and traceability.

Applications

ASTM D7137/D7137M-23 is widely used in several industrial and research contexts:

• Material Specification and Qualification: Assists manufacturers in characterizing CAI strength for multilayered composite laminates, a critical property in aerospace, automotive, and wind energy applications.
• Product Development: Provides critical comparative data for selecting composite materials with high damage tolerance, enabling optimized designs for lightweight structural components.
• Damage Tolerance Assessment: Offers valuable guidance on the post-damage compressive performance of composites with similar material composition, layup, and thickness.
• Research and Development: Supports academic and industrial research seeking to understand and enhance the damage resistance and residual strength of advanced composites.
• Quality Control (Limited Value): While not generally used for quality assurance due to variability, it provides supplementary information regarding potential performance following impact events.

Note: Due to the influence of laminate design, geometry, damage size/location, and edge support, the compressive residual strength data is not usually scalable to different configurations or for setting design allowables in structural design.

Related Standards

For effective and standardized composite material testing, the following referenced standards are highly relevant:

• ASTM D7136/D7136M – Drop-weight impact resistance of fiber-reinforced polymer matrix composites.
• ASTM D6264/D6264M – Quasi-static indentation damage resistance.
• ASTM D6641/D6641M – Compressive properties of undamaged polymer matrix composites.
• ASTM D5687/D5687M – Preparation of flat composite panels with processing guidelines.
• ASTM D3171 – Constituent content of composite materials.
• ASTM D5229/D5229M – Moisture absorption and equilibrium conditioning.
• ASTM D3878, D883, E6, E177, E122, E456 – Terminology and statistical practices for composite materials and test results.

Summary

ASTM D7137/D7137M-23 provides a critical, standardized approach for the assessment of compressive residual strength in damaged polymer matrix composite plates. It is indispensable for engineers, material scientists, and quality professionals focused on the performance and durability of composite structures subjected to real-world impact and indentation damage. Consistent use of this standard helps ensure reliable, comparable data for material development and selection across industries dedicated to high-performance composites.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7137/D7137M − 23
Standard Test Method for
Compressive Residual Strength Properties of Damaged
Polymer Matrix Composite Plates
This standard is issued under the fixed designation D7137/D7137M; 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.
1. Scope system shall be used independently of the other, and values
from the two systems shall not be combined.
1.1 This test method covers compression residual strength
1.5.1 Within the text the inch-pound units are shown in
properties of multidirectional polymer matrix composite lami-
brackets.
nated plates, which have been subjected to quasi-static inden-
1.6 This standard does not purport to address all of the
tation per Test Method D6264/D6264M or drop-weight impact
safety concerns, if any, associated with its use. It is the
per Test Method D7136/D7136M prior to application of
responsibility of the user of this standard to establish appro-
compressive force. The composite material forms are limited to
priate safety, health, and environmental practices and deter-
continuous-fiber reinforced polymer matrix composites with
mine the applicability of regulatory limitations prior to use.
multidirectional fiber orientations, and which are both symmet-
1.7 This international standard was developed in accor-
ric and balanced with respect to the test direction. The range of
dance with internationally recognized principles on standard-
acceptable test laminates and thicknesses is defined in 8.2.
NOTE 1—When used to determine the residual strength of drop-weight ization established in the Decision on Principles for the
impacted plates, this test method is commonly referred to as the
Development of International Standards, Guides and Recom-
Compression After Impact, or CAI, method.
mendations issued by the World Trade Organization Technical
1.2 The method utilizes a flat, rectangular composite plate,
Barriers to Trade (TBT) Committee.
previously subjected to a damaging event, which is tested
under compressive loading using a stabilization fixture. 2. Referenced Documents
NOTE 2—The damage tolerance properties obtained are particular to the
2.1 ASTM Standards:
type, geometry and location of damage inflicted upon the plate.
D792 Test Methods for Density and Specific Gravity (Rela-
1.3 The properties generated by this test method are highly
tive Density) of Plastics by Displacement
dependent upon several factors, which include specimen
D883 Terminology Relating to Plastics
geometry, layup, damage type, damage size, damage location,
D3171 Test Methods for Constituent Content of Composite
and boundary conditions. Thus, results are generally not
Materials
scalable to other configurations, and are particular to the
D3878 Terminology for Composite Materials
combination of geometric and physical conditions tested.
D5229/D5229M Test Method for Moisture Absorption Prop-
1.4 This test method can be used to test undamaged polymer erties and Equilibrium Conditioning of Polymer Matrix
matrix composite plates, but historically such tests have
Composite Materials
demonstrated a relatively high incidence of undesirable failure D5687/D5687M Guide for Preparation of Flat Composite
modes (such as end crushing). Test Method D6641/D6641M is Panels with Processing Guidelines for Specimen Prepara-
recommended for obtaining compressive properties of undam- tion
aged polymer matrix composites. D6264/D6264M Test Method for Measuring the Damage
Resistance of a Fiber-Reinforced Polymer-Matrix Com-
1.5 Units—The values stated in either SI units or inch-
posite to a Concentrated Quasi-Static Indentation Force
pound units are to be regarded separately as standard. The
D6641/D6641M Test Method for Compressive Properties of
values stated in each system are not necessarily exact equiva-
Polymer Matrix Composite Materials Using a Combined
lents; therefore, to ensure conformance with the standard, each
Loading Compression (CLC) Test Fixture
D7136/D7136M Test Method for Measuring the Damage
This test method is under the jurisdiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.05 on
Structural Test Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2023. Published June 2023. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2005. Last previous edition approved in 2017 as D7137/D7137M – 17. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D7137_D7137M-23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7137/D7137M − 23
Resistance of a Fiber-Reinforced Polymer Matrix Com- 3.2.2 nominal value, n—a value, existing in name only,
posite to a Drop-Weight Impact Event assigned to a measurable property for the purpose of conve-
E4 Practices for Force Calibration and Verification of Test- nient designation. Tolerances may be applied to a nominal
ing Machines value to define an acceptable range for the property.
E6 Terminology Relating to Methods of Mechanical Testing
3.3 Symbols:
E122 Practice for Calculating Sample Size to Estimate, With
3.3.1 A—cross-sectional area of a specimen
Specified Precision, the Average for a Characteristic of a
3.3.2 CV—coefficient of variation statistic of a sample
Lot or Process
population for a given property (in percent)
E177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
3.3.3 D—damage diameter
E456 Terminology Relating to Quality and Statistics
CAI
3.3.4 E —effective compressive modulus in the test direc-
2.2 Military Standards:
tion
NASA Reference Publication 1092 Standard Tests for
CAI
3.3.5 F —ultimate compressive residual strength in the
Toughened Resin Composites, Revised Edition, July
test direction
3.3.6 h—specimen thickness
3. Terminology
3.3.7 l—specimen length
3.1 Definitions—Terminology D3878 defines terms relating
3.3.8 n—number of specimens per sample population
to composite materials. Terminology D883 defines terms
relating to plastics. Terminology E6 defines terms relating to
3.3.9 N—number of plies in laminate under test
mechanical testing. Terminology E456 and Practice E177
3.3.10 P —maximum force carried by test specimen prior
max
define terms relating to statistics. In the event of a conflict
to failure
between terms, Terminology D3878 shall have precedence
over the other standards.
3.3.11 S —standard deviation statistic of a sample popu-
n-1
lation for a given property
3.2 Definitions of Terms Specific to This Standard:
3.2.1 If the term represents a physical quantity, its analytical
3.3.12 w—specimen width
dimensions are stated immediately following the term (or letter
3.3.13 x —test result for an individual specimen from the
i
symbol) in fundamental dimension form, using the following
sample population for a given property
ASTM standard symbology for fundamental dimensions,
shown within square brackets: [M] for mass, [L] for length, [T] 3.3.14 x¯—mean or average (estimate of mean) of a sample
for time, [θ] for thermodynamic temperature, and [nd] for
population for a given property
non-dimensional quantities. Use of these symbols is restricted
to analytical dimensions when used with square brackets, as
4. Summary of Test Method
the symbols may have other definitions when used without the
4.1 A uniaxial compression test is performed using a
brackets.
balanced, symmetric laminated plate, which has been damaged
and inspected prior to the application of compressive force.
The damage state is imparted through out-of-plane loading
caused by quasi-static indentation or drop-weight impact.
Available from National Aeronautics and Space Administration (NASA)-
Langley Research Center, Hampton, VA 23681-2199.
FIG. 1 Schematic of Compressive Residual Strength Support Fixture with Specimen in Place
D7137/D7137M − 23
FIG. 2 Support Fixture Assembly
FIG. 3 Support Fixture Base Plate (Inch-Pound Version)
D7137/D7137M − 23
FIG. 4 Support Fixture Base Plate (SI Version)
FIG. 5 Support Fixture Angles (Inch-Pound Version)
4.1.1 Quasi-Static Indentation—The rectangular plate is and induced specimen bending. The specimen/fixture assembly
damaged due to application of an out-of-plane static indenta- is placed between flat platens and end-loaded under compres-
tion force in accordance with Test Method D6264/D6264M. sive force until failure. Applied force, crosshead displacement,
4.1.2 Drop-Weight Impact—The rectangular plate is dam- and strain data are recorded while loading.
aged due to application of an out-of-plane drop-weight impact
4.3 Preferred failure modes pass through the damage in the
in accordance with Test Method D7136/D7136M.
test specimen. However, acceptable failures may initiate away
4.2 The damaged plate is installed in a multi-piece support from the damage site, in instances when the damage produces
fixture, that has been aligned to minimize loading eccentricities a relatively low stress concentration or if the extent of damage
D7137/D7137M − 23
FIG. 6 Support Fixture Angles (SI Version)
FIG. 7 Support Fixture Side Plates and Base Slideplates (Inch-Pound Version)
is small, or both. Unacceptable failure modes are those related to load introduction by the support fixture, local edge support
D7137/D7137M − 23
FIG. 8 Support Fixture Side Plates and Base Slideplates (SI Version)
conditions, and specimen instability (unless the specimen is stiffness, support conditions, and so forth. Significant differ-
dimensionally representative of a particular structural applica- ences in the relationships between the existent damage state
tion). and the residual compressive strength can result due to
differences in these parameters. For example, residual strength
5. Significance and Use
and stiffness properties obtained using this test method would
5.1 Susceptibility to damage from concentrated out-of-plane more likely reflect the damage tolerance characteristics of an
un-stiffened monolithic skin or web than that of a skin attached
forces is one of the major design concerns of many structures
to substructure which resists out-of-plane deformation.
made of advanced composite laminates. Knowledge of the
damage resistance and damage tolerance properties of a Similarly, test specimen properties would be expected to be
similar to those of a panel with equivalent length and width
laminated composite plate is useful for product development
and material selection. dimensions, in comparison to those of a panel significantly
larger than the test specimen.
5.2 The residual strength data obtained using this test
method is most commonly used in material specifications and 5.4 The reporting section requires items that tend to influ-
research and development activities. The data are not intended ence residual compressive strength to be reported; these
for use in establishing design allowables, as the results are include the following: material, methods of material
fabrication, accuracy of lay-up orientation, laminate stacking
specific to the geometry and physical conditions tested and are
generally not scalable to other configurations. Its usefulness in sequence and overall thickness, specimen geometry, specimen
preparation, specimen conditioning, environment of testing,
establishing quality assurance requirements is also limited, due
to the inherent variability of induced damage, as well as the void content, volume percent reinforcement, type, size and
location of damage (including method of non-destructive
dependency of damage tolerance response upon the pre-
existent damage state. inspection), specimen/fixture alignment and gripping, time at
temperature, and speed of testing.
5.3 The properties obtained using this test method can
provide guidance in regard to the anticipated damage tolerance 5.5 Properties that result from the residual strength assess-
capability of composite structures of similar material, ment include the following: compressive residual strength
CAI
thickness, stacking sequence, and so forth. However, it must be F , compressive force as a function of crosshead
understood that the damage tolerance of a composite structure displacement, and surface strains as functions of crosshead
is highly dependent upon several factors including geometry, displacement.
D7137/D7137M − 23
FIG. 9 Support Fixture Top Plate and Top Slideplates (Inch-Pound Version)
6. Interferences 6.3 Damage Type—Variations in the composite failure
modes produced during the damaging event can contribute to
6.1 The response of a damaged specimen is dependent upon
strength, stiffness and strain data scatter.
many factors, such as laminate thickness, ply thickness, stack-
ing sequence, environment, damage type, damage geometry, 6.4 Damage Geometry and Location—The size, shape, and
damage location, and loading/support conditions. location of damage (both within the plane of the plate and
Consequently, comparisons cannot be made between materials through-the-thickness) can affect the deformation and strength
unless identical test configurations, test conditions, and lami- behavior of the specimens significantly. Edge effects, boundary
nate configurations are used. Therefore, all deviations from the constraints, and the damaged stress/strain field can interact if
standard test configuration shall be reported in the results. the damage size becomes too large relative to the length and
Specific structural configurations and boundary conditions width dimensions of the plate. It is recommended that the
must be considered when applying the data generated using damage size be limited to half the unsupported specimen width
this test method to design applications. (42 mm [1.7 in.]) to minimize interaction between damage and
edge-related stress/strain fields; as the specimen has a small
6.2 Material and Specimen Preparation—Poor material fab-
length-to-width aspect ratio of 1.5, its stress/strain distribution
rication practices, lack of control of fiber alignment, and
is particularly sensitive to disturbances caused by impact or
damage induced by improper specimen machining are known
indentation damage.
causes of high material data scatter in composites in general.
Important aspects of plate specimen preparation that contribute
to data scatter include thickness variation, out-of-plane
Eastland, C., Coxon, B., Avery, W., and Flynn, B., “Effects of Aspect Ratio on
curvature, surface roughness, and failure to meet the dimen-
Test Results from Compression-Loaded Composite Coupons,” Proceedings of
sional and squareness tolerances (parallelism and perpendicu-
ICCM X, Whistler, BC, Vol IV, A. Poursartip and K. Street, eds., Woodhead
larity) specified in 8.2.2. Publishing, Ltd., 1995.
D7137/D7137M − 23
FIG. 10 Support Fixture Top Plate and Top Slideplates (SI Version)
NOTE 3—To investigate the effects of larger damage sizes upon
machine, and shimmed to apply an essentially uniaxial dis-
composite laminate compressive residual strength, it is recommended to
placement to the loaded end of the specimen.
examine alternative specimen and fixture designs, such as NASA 1092,
which are larger and can accommodate larger damage areas without 6.7 Material Orthotropy—The degree of laminate orthot-
significant interaction from edge support conditions.
ropy strongly affects the failure mode and measured compres-
6.5 Test Fixture Characteristics—The configuration of the sive residual strength. Valid strength results should only be
panel edge-constraint structure can have a significant effect on reported when appropriate failure modes are observed, in
test results. In the standard test fixture, the top and bottom accordance with 11.15.
supports provide no clamp-up, but provide some restraint to
6.8 Non-Destructive Inspection—Non-destructive inspec-
local out-of-plane rotation due to the fixture geometry. The side
tion (NDI) results are affected by the particular method
supports are knife edges, which provide no rotational restraint.
utilized, the inherent variability of the NDI method, the
Edge supports must be co-planar. Results are affected by the
experience of the operator, and so forth.
geometry of the various slide plates local to the specimen.
6.9 Panel Instability—Accurate detection of instability or
Results are also affected by the presence of gaps between the
incipient instability may not be possible. The nature of the
slide plates and the specimen, which can reduce the effective
damage can have a significant effect upon local flexural
edge support and can result in concentrated load introduction
rigidity, which may complicate the failure mode, limiting the
conditions at the top and bottom specimen surfaces.
data only to the unique configuration tested.
Additionally, results may be affected by variations in torque
applied to the slide plate fasteners; loose fasteners may also
7. Apparatus
reduce the effective edge support.
6.6 System Alignment—Errors can result if the test fixture is 7.1 Micrometers and Calipers—A micrometer with a 4 mm
not centered with respect to the loading axis of the test to 8 mm [0.16 in. to 0.32 in.] nominal diameter ball-interface
D7137/D7137M − 23
FIG. 11 Compressive Residual Strength Test Specimen (Inch-Pound Version)
FIG. 12 Compression Residual Strength Test Specimen (SI Version)
D7137/D7137M − 23
FIG. 13 Commonly Observed Acceptable Compressive Residual Strength Failure Modes
or a flat anvil interface shall be used to measure the specimen specimen. The side plates are sufficiently short to ensure that a
thickness. A ball interface is recommended for thickness gap between the side rails and the top plate is maintained
measurements when at least one surface is irregular (for during the test.
example, a coarse peel ply surface, which is neither smooth nor
7.2.1 Support Fixture Details—Detailed drawings for manu-
flat). A micrometer or caliper with a flat anvil interface shall be
facturing the support fixture that satisfy the requirements of
used for measuring length, width, other machined surface
this test method are contained in Figs. 3-10. The fixture shall be
dimensions, and damage dimensions. The use of alternative
constructed of sufficient stiffness and precision as to satisfy the
measurement devices is permitted if specified (or agreed to) by
loading uniformity requirements of this test method. The
the test requestor and reported by the testing laboratory. The
following general notes apply to these figures: The fixture
accuracy of the instrument(s) shall be suitable for reading to
shall be constructed of sufficient stiffness and precision as to
within 1 % of the specimen dimensions. For typical specimen
satisfy the loading uniformity requirements of this test method.
geometries, an instrument with an accuracy of 60.0025 mm
The following general notes apply to these figures:
[60.0001 in.] is adequate for thickness measurements, while
7.2.1.1 Machine surfaces to a 3.2 [125] surface finish unless
an instrument with an accuracy of 60.025 mm [60.001 in.] is
otherwise specified.
adequate for measurement of length, width, other machined
7.2.1.2 Break all edges.
surface dimensions, and damage dimensions.
7.2.1.3 The test fixture shall be made of steel. It may be
7.2 Support Fixture—The compressive test fixture, shown in
made of low carbon steel for ambient temperature testing. For
Figs. 1 and 2, utilizes adjustable retention plates to support the non-ambient environmental conditions, the recommended fix-
specimen edges and inhibit buckling when the specimen is
ture material is a nonheat-treated ferritic or precipitation
end-loaded. The fixture consists of one base plate, two base hardened stainless steel (heat treatment for improved durability
slideplates, two angles, four side plates, one top plate, and two
is acceptable but not required).
top slideplates. Alternate fixtures with angles integrated into NOTE 4—Experience has shown that fixtures may be damaged due to
handling in use, thus periodic re-inspection of the fixture dimensions and
the base plate are permissible. The side supports are knife
tolerances is important.
edges, which provide no restraint to local out-of-plane rotation.
The top and bottom supports provide no clamp-up, but provide
some rotational restraint due to the fixture geometry (the slide
plates have a squared geometry and overlap the specimen by 8
Other fixtures that meet the requirements of this section may be used (for
example, Wyoming Test Fixtures, Inc. Model CU-CI, Boeing BSS-7260 Type II,
mm [0.30 in.]). The fixture is adjustable to accommodate small
Airbus AITM 1.0010, SACMA SRM 2R-94). If you are aware of alternative
variations in specimen length, width and thickness. The top
suppliers, please provide this information to ASTM International Headquarters.
plate and slide plates, which are not directly attached to the
Your comments will receive careful consideration at a meeting of the responsible
lower portion of the fixture, slip over the top edge of the test technical committee, which you may attend.
D7137/D7137M − 23
7.3 Testing Machine—The testing machine shall be in con- any single specimen. The gages, surface preparation, and
formance with Practices E4, and shall satisfy the following bonding agents should be chosen to provide for optimal
requirements: performance on the subject material for the prescribed test
environment. Attachment of the strain-indicating device to the
7.3.1 Testing Machine Configuration—The testing machine
specimen shall not cause damage to the specimen surface.
shall have both an essentially stationary head and a movable
NOTE 5—Although the compression test may be performed without the
head. A short loading train and flat end-loading platens shall be
use of strain-indicating devices, lack of instrumentation for the damaged
used.
specimens makes the detection of undesirable panel instability much more
7.3.2 Flat Platens—The test machine shall be mounted with
difficult. For this reason, strain measurement of the test specimens during
well-aligned, fixed (as opposed to spherical seat) flat platens.
compressive loading is recommended.
NOTE 6—Moisture proofing of the strain gage installations on the
The platen surfaces shall be parallel within 0.025 mm [0.001
specimen needs to be done very carefully with multiple layers of
in.] across the test fixture top plate length of 100 mm [4.0 in.].
protective coatings (such as microfined wax, high temperature Teflon tape,
If the platens are not sufficiently hardened, or simply to protect
adhesively-bonded aluminum foil, and room temperature curing vulcaniz-
the platen surfaces, a hardened plate (with parallel surfaces)
ing (RTV) compound) before subjecting them to moisture conditioning
can be inserted between each end of the fixture and the inside the environmental conditioning chamber. Foil strain gages, pro-
tected simply with RTV compound, are likely to become corroded and
corresponding platen. The lower platen should be marked to
unfit for hot-wet testing after approximately 100 days of moisture
help center the test fixture between the platens.
conditioning.
7.3.3 Drive Mechanism—The testing machine drive mecha-
7.7 Data Acquisition Equipment—Equipment capable of
nism shall be capable of imparting to the movable head a
recording force, crosshead displacement, and strain data is
controlled velocity with respect to the stationary head. The
required.
velocity of the movable head shall be capable of being
regulated as specified in 11.5. 7.8 Alignment Plate—If individual test specimens are not
instrumented for strain measurement, an instrumented align-
7.3.4 Force Indicator—The testing machine force-sensing
ment plate shall be used to align the support fixture. The
device shall be capable of indicating the total force being
alignment plate should be equivalent to the test specimens in
carried by the test specimen. This device shall be essentially
terms of material, layup, and geometry, shall be un-damaged,
free from inertia-lag at the specified rate of testing and shall
and shall be instrumented as described in 7.6. Alternatively, an
indicate the force with an accuracy over the force range(s) of
instrumented metallic plate, equivalent in thickness to the test
interest of within 61 % of the indicated value.
specimens to within 60.25 mm [60.010 in.], may be used in
7.3.5 Crosshead Displacement Indicator—The testing ma-
support fixture alignment.
chine shall be capable of monitoring and recording the cross-
head displacement (stroke) with a precision of at least 61 %.
8. Sampling and Test Specimens
If machine compliance is significant, it is acceptable to
8.1 Sampling—Test at least five specimens per test condi-
measure the displacement of the movable head using a LVDT
tion unless valid results can be gained through the use of fewer
or similar device with 61 % precision on displacement.
specimens, as in the case of a designed experiment. For
7.4 Conditioning Chamber—.When conditioning materials
statistically significant data the procedures outlined in Practice
at non-laboratory environments, a temperature-/vapor-level
E122 should be consulted. The method of sampling shall be
controlled environmental conditioning chamber is required that
reported.
shall be capable of maintaining the required temperature to
8.2 Geometry:
within 63 °C [65 °F] and the required relative humidity level
8.2.1 Stacking Sequence—For comparison screening of the
to within 63 % RH. Chamber conditions shall be monitored
compressive residual strength of different materials, the stan-
either on an automated continuous basis or on a manual basis
dard specimen thickness shall be 4.0 mm to 6.0 mm [0.16 in. to
at regular intervals.
0.24 in.] with a target thickness of 5.0 mm [0.20 in.] and the
7.5 Environmental Test Chamber—An environmental test
laminate defined as follows:
chamber is required for test environments other than ambient
8.2.1.1 Unidirectional Tape—Laminate construction shall
testing laboratory conditions. This chamber shall be capable of
consist of the appropriate number of unidirectional plies to
maintaining the test specimen and fixture at the required test
achieve a total cured thickness nearest to 5.0 mm [0.20 in.]
environment during the mechanical test. The test temperature
with a stacking sequence of [45/0/-45/90] where N is a
NS
shall be maintained within 63 °C [65 °F] of the required
whole number. If the “nearest” thickness is less than 4.0 mm
temperature. The relative humidity level controlled within the
[0.16 in.], the next value of N shall be used (N+1). Recom-
test chamber shall be defined by the test requestor.
mended layups for various nominal cured ply thicknesses are
provided in Table 1. The laminated plate layup is to be defined
7.6 Strain-Indicating Device—Strain measurement of the
such that the 0° fiber orientation is aligned with the lengthwise
specimens is recommended, but not required. If strain mea-
(long) dimension.
surement is performed, the longitudinal strain should be
measured simultaneously at four locations (two locations on
opposite faces of the specimen as shown in Figs. 11 and 12) to
Vijayaraju, K., Mangalgiri, P. D., and Parida B. K., “Hot-Wet Compression
aid in ensuring application of pure compressive loading and to
Testing of Impact Damaged Composite Laminates,” Proceedings of the Ninth
detect bending or buckling, or both, if any. The same type of
International Conference on Fracture (ICF-9), Sydney, Australia, 1997, pp. 909-
str
...

This document is not an ASTM 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. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7137/D7137M − 17 D7137/D7137M − 23
Standard Test Method for
Compressive Residual Strength Properties of Damaged
Polymer Matrix Composite Plates
This standard is issued under the fixed designation D7137/D7137M; 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.
1. 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 D6264/D6264M or drop-weight impact per Test
Method D7136/D7136M 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 8.2.
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 D6641/D6641M is recommended for
obtaining compressive properties of undamaged polymer matrix composites.
1.5 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in
each system may not beare not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall
be used independently of the other. Combiningother, and values from the two systems may result in non-conformance with the
standard.shall not be combined.
1.5.1 Within the text the inch-pound units are shown in brackets.
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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.05 on Structural Test
Methods.
Current edition approved Oct. 15, 2017May 1, 2023. Published October 2017.June 2023. Originally approved in 2005. Last previous edition approved in 20122017 as
D7137/D7137MD7137/D7137M – 17.-12. DOI: 10.1520/D7137_D7137M-17.10.1520/D7137_D7137M-23.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7137/D7137M − 23
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement
D883 Terminology Relating to Plastics
D3171 Test Methods for Constituent Content of Composite Materials
D3878 Terminology for Composite Materials
D5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite
Materials
D5687/D5687M Guide for Preparation of Flat Composite Panels with Processing Guidelines for Specimen Preparation
D6264/D6264M Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer-Matrix Composite to a
Concentrated Quasi-Static Indentation Force
D6641/D6641M Test Method for Compressive Properties of Polymer Matrix Composite Materials Using a Combined Loading
Compression (CLC) Test Fixture
D7136/D7136M Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer Matrix Composite to a
Drop-Weight Impact Event
E4 Practices for Force Calibration and Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or
Process
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
2.2 Military Standards:
NASA Reference Publication 1092 Standard Tests for Toughened Resin Composites, Revised Edition, July 1983
3. Terminology
3.1 Definitions—Terminology D3878 defines terms relating to composite materials. Terminology D883 defines terms relating to
plastics. Terminology E6 defines terms relating to mechanical testing. Terminology E456 and Practice E177 define terms relating
to statistics. In the event of a conflict between terms, Terminology D3878 shall have precedence over the other standards.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 If the term represents a physical quantity, its analytical dimensions are stated immediately following the term (or letter
symbol) in fundamental dimension form, using the following ASTM standard symbology for fundamental dimensions, shown
within square brackets: [M] for mass, [L] for length, [T] for time, [θ] for thermodynamic temperature, and [nd] for non-dimensional
quantities. Use of these symbols is restricted to analytical dimensions when used with square brackets, as the symbols may have
other definitions when used without the brackets.
3.2.2 nominal value, n—a value, existing in name only, assigned to a measurable property for the purpose of convenient
designation. Tolerances may be applied to a nominal value to define an acceptable range for the property.
3.2.3 principal material coordinate system, n—a coordinate system with axes that are normal to the planes of symmetry inherent
to a material.
3.2.3.1 Discussion—
Common usage, at least for Cartesian axes (123,xyz, and so forth), generally assigns the coordinate system axes to the normal
directions of planes of symmetry in order that the highest property value in a normal direction (for elastic properties, the axis of
greatest stiffness) would be 1 or x, and the lowest (if applicable) would be 3 or z. Anisotropic materials do not have a principal
material coordinate system due to the total lack of symmetry, while, for isotropic materials, any coordinate system is a principal
material coordinate system. In laminated composites, the principal material coordinate system has meaning only with respect to
an individual orthotropic lamina. The related term for laminated composites is “reference coordinate system.”
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from National Aeronautics and Space Administration (NASA)-Langley Research Center, Hampton, VA 23681-2199.
D7137/D7137M − 23
3.2.4 reference coordinate system, n—a coordinate system for laminated composites used to define ply orientations. One of the
reference coordinate system axes (normally the Cartesian x-axis) is designated the reference axis, assigned a position, and the ply
principal axis of each ply in the laminate is referenced relative to the reference axis to define the ply orientation for that ply.
3.2.5 specially orthotropic, adj—a description of an orthotropic material as viewed in its principal material coordinate system. In
laminated composites, a specially orthotropic laminate is a balanced and symmetric laminate of the [0 /90 ] family as viewed from
i j ns
the reference coordinate system, such that the membrane-bending coupling terms of the laminate constitutive relation are zero.
3.3 Symbols: A = cross-sectional area of a specimen
CV = coefficient of variation statistic of a sample population for a given property (in percent)
D = damage diameter
CAI
E = effective compressive modulus in the test direction
CAI
F = ultimate compressive residual strength in the test direction
h = specimen thickness
l = specimen length
n = number of specimens per sample population
N = number of plies in laminate under test
P = maximum force carried by test specimen prior to failure
max
S = standard deviation statistic of a sample population for a given property
n-1
w = specimen width
x = test result for an individual specimen from the sample population for a given property
i
x¯ = mean or average (estimate of mean) of a sample population for a given property
3.3 Symbols:
3.3.1 A—cross-sectional area of a specimen
3.3.2 CV—coefficient of variation statistic of a sample population for a given property (in percent)
3.3.3 D—damage diameter
CAI
3.3.4 E —effective compressive modulus in the test direction
CAI
3.3.5 F —ultimate compressive residual strength in the test direction
3.3.6 h—specimen thickness
FIG. 1 Schematic of Compressive Residual Strength Support Fixture with Specimen in Place
D7137/D7137M − 23
3.3.7 l—specimen length
3.3.8 n—number of specimens per sample population
3.3.9 N—number of plies in laminate under test
3.3.10 P —maximum force carried by test specimen prior to failure
max
3.3.11 S —standard deviation statistic of a sample population for a given property
n-1
3.3.12 w—specimen width
3.3.13 x —test result for an individual specimen from the sample population for a given property
i
3.3.14 x¯—mean or average (estimate of mean) of a sample population for a given property
4. Summary of Test Method
FIG. 2 Support Fixture Assembly
D7137/D7137M − 23
FIG. 3 Support Fixture Base Plate (Inch-Pound Version)
FIG. 4 Support Fixture Base Plate (SI Version)
4.1 A uniaxial compression test is performed using a balanced, symmetric laminated plate, which has been damaged and inspected
prior to the application of compressive force. The damage state is imparted through out-of-plane loading caused by quasi-static
indentation or drop-weight impact.
4.1.1 Quasi-Static Indentation—The rectangular plate is damaged due to application of an out-of-plane static indentation force in
accordance with Test Method D6264/D6264M.
4.1.2 Drop-Weight Impact—The rectangular plate is damaged due to application of an out-of-plane drop-weight impact in
accordance with Test Method D7136/D7136M.
4.2 The damaged plate is installed in a multi-piece support fixture, that has been aligned to minimize loading eccentricities and
induced specimen bending. The specimen/fixture assembly is placed between flat platens and end-loaded under compressive force
until failure. Applied force, crosshead displacement, and strain data are recorded while loading.
4.3 Preferred failure modes pass through the damage in the test specimen. However, acceptable failures may initiate away from
the damage site, in instances when the damage produces a relatively low stress concentration or if the extent of damage is small,
D7137/D7137M − 23
FIG. 5 Support Fixture Angles (Inch-Pound Version)
FIG. 6 Support Fixture Angles (SI Version)
D7137/D7137M − 23
FIG. 7 Support Fixture Side Plates and Base Slideplates (Inch-Pound Version)
FIG. 8 Support Fixture Side Plates and Base Slideplates (SI Version)
or both. Unacceptable failure modes are those related to load introduction by the support fixture, local edge support conditions,
and specimen instability (unless the specimen is dimensionally representative of a particular structural application).
D7137/D7137M − 23
FIG. 9 Support Fixture Top Plate and Top Slideplates (Inch-Pound Version)
5. Significance and Use
5.1 Susceptibility to damage from concentrated out-of-plane forces is one of the major design concerns of many structures made
of advanced composite laminates. Knowledge of the damage resistance and damage tolerance properties of a laminated composite
plate is useful for product development and material selection.
5.2 The residual strength data obtained using this test method is most commonly used in material specifications and research and
development activities. The data are not intended for use in establishing design allowables, as the results are specific to the
geometry and physical conditions tested and are generally not scalable to other configurations. Its usefulness in establishing quality
assurance requirements is also limited, due to the inherent variability of induced damage, as well as the dependency of damage
tolerance response upon the pre-existent damage state.
5.3 The properties obtained using this test method can provide guidance in regard to the anticipated damage tolerance capability
of composite structures of similar material, thickness, stacking sequence, and so forth. However, it must be understood that the
damage tolerance of a composite structure is highly dependent upon several factors including geometry, stiffness, support
conditions, and so forth. Significant differences in the relationships between the existent damage state and the residual compressive
strength can result due to differences in these parameters. For example, residual strength and stiffness properties obtained using
this test method would more likely reflect the damage tolerance characteristics of an un-stiffened monolithic skin or web than that
of a skin attached to substructure which resists out-of-plane deformation. Similarly, test specimen properties would be expected
to be similar to those of a panel with equivalent length and width dimensions, in comparison to those of a panel significantly larger
than the test specimen.
D7137/D7137M − 23
FIG. 10 Support Fixture Top Plate and Top Slideplates (SI Version)
5.4 The reporting section requires items that tend to influence residual compressive strength to be reported; these include the
following: material, methods of material fabrication, accuracy of lay-up orientation, laminate stacking sequence and overall
thickness, specimen geometry, specimen preparation, specimen conditioning, environment of testing, void content, volume percent
reinforcement, type, size and location of damage (including method of non-destructive inspection), specimen/fixture alignment and
gripping, time at temperature, and speed of testing.
CAI
5.5 Properties that result from the residual strength assessment include the following: compressive residual strength F ,
compressive force as a function of crosshead displacement, and surface strains as functions of crosshead displacement.
6. Interferences
6.1 The response of a damaged specimen is dependent upon many factors, such as laminate thickness, ply thickness, stacking
sequence, environment, damage type, damage geometry, damage location, and loading/support conditions. Consequently,
comparisons cannot be made between materials unless identical test configurations, test conditions, and laminate configurations
are used. Therefore, all deviations from the standard test configuration shall be reported in the results. Specific structural
configurations and boundary conditions must be considered when applying the data generated using this test method to design
applications.
6.2 Material and Specimen Preparation—Poor material fabrication practices, lack of control of fiber alignment, and damage
induced by improper specimen machining are known causes of high material data scatter in composites in general. Important
D7137/D7137M − 23
FIG. 11 Compressive Residual Strength Test Specimen (Inch-Pound Version)
FIG. 12 Compression Residual Strength Test Specimen (SI Version)
D7137/D7137M − 23
FIG. 13 Commonly Observed Acceptable Compressive Residual Strength Failure Modes
aspects of plate specimen preparation that contribute to data scatter include thickness variation, out-of-plane curvature, surface
roughness, and failure to meet the dimensional and squareness tolerances (parallelism and perpendicularity) specified in 8.2.2.
6.3 Damage Type—Variations in the composite failure modes produced during the damaging event can contribute to strength,
stiffness and strain data scatter.
6.4 Damage Geometry and Location—The size, shape, and location of damage (both within the plane of the plate and
through-the-thickness) can affect the deformation and strength behavior of the specimens significantly. Edge effects, boundary
constraints, and the damaged stress/strain field can interact if the damage size becomes too large relative to the length and width
dimensions of the plate. It is recommended that the damage size be limited to half the unsupported specimen width (42 mm [1.7
in.]) to minimize interaction between damage and edge-related stress/strain fields; as the specimen has a small length-to-width
aspect ratio of 1.5, its stress/strain distribution is particularly sensitive to disturbances caused by impact or indentation damage.
NOTE 3—To investigate the effects of larger damage sizes upon composite laminate compressive residual strength, it is recommended to examine
alternative specimen and fixture designs, such as NASA 1092, which are larger and can accommodate larger damage areas without significant interaction
from edge support conditions.
6.5 Test Fixture Characteristics—The configuration of the panel edge-constraint structure can have a significant effect on test
results. In the standard test fixture, the top and bottom supports provide no clamp-up, but provide some restraint to local
out-of-plane rotation due to the fixture geometry. The side supports are knife edges, which provide no rotational restraint. Edge
supports must be co-planar. Results are affected by the geometry of the various slide plates local to the specimen. Results are also
affected by the presence of gaps between the slide plates and the specimen, which can reduce the effective edge support and can
result in concentrated load introduction conditions at the top and bottom specimen surfaces. Additionally, results may be affected
by variations in torque applied to the slide plate fasteners; loose fasteners may also reduce the effective edge support.
6.6 System Alignment—Errors can result if the test fixture is not centered with respect to the loading axis of the test machine, and
shimmed to apply an essentially uniaxial displacement to the loaded end of the specimen.
Eastland, C., Coxon, B., Avery, W., and Flynn, B., “Effects of Aspect Ratio on Test Results from Compression-Loaded Composite Coupons,” Proceedings of ICCM X,
Whistler, BC, Vol IV, A. Poursartip and K. Street, eds., Woodhead Publishing, Ltd., 1995.
D7137/D7137M − 23
6.7 Material Orthotropy—The degree of laminate orthotropy strongly affects the failure mode and measured compressive residual
strength. Valid strength results should only be reported when appropriate failure modes are observed, in accordance with 11.15.
6.8 Non-Destructive Inspection—Non-destructive inspection (NDI) results are affected by the particular method utilized, the
inherent variability of the NDI method, the experience of the operator, and so forth.
6.9 Panel Instability—Accurate detection of instability or incipient instability may not be possible. The nature of the damage can
have a significant effect upon local flexural rigidity, which may complicate the failure mode, limiting the data only to the unique
configuration tested.
7. Apparatus
7.1 Micrometers and Calipers—A micrometer with a 4 to 7 mm [0.16 to 0.28 in.] 4 mm to 8 mm [0.16 in. to 0.32 in.] nominal
diameter ball-interface or a flat anvil interface shall be used to measure the specimen thickness. A ball interface is recommended
for thickness measurements when at least one surface is irregular (e.g. a course peel ply surface(for example, a coarse peel ply
surface, which is neither smooth nor flat). A micrometer or caliper with a flat anvil interface shall be used for measuring length,
width, other machined surface dimensions, and damage dimensions. The use of alternative measurement devices is permitted if
specified (or agreed to) by the test requestor and reported by the testing laboratory. The accuracy of the instrument(s) shall be
suitable for reading to within 1 % of the specimen dimensions. For typical specimen geometries, an instrument with an accuracy
of 60.0025 mm [60.0001 in.] is adequate for thickness measurements, while an instrument with an accuracy of 60.025 mm
[60.001 in.] is adequate for measurement of length, width, other machined surface dimensions, and damage dimensions.
7.2 Support Fixture—The compressive test fixture, shown in Figs. 1 and 2, utilizes adjustable retention plates to support the
specimen edges and inhibit buckling when the specimen is end-loaded. The fixture consists of one base plate, two base slideplates,
two angles, four side plates, one top plate, and two top slideplates. Alternate fixtures with angles integrated into the base plate are
permissible. The side supports are knife edges, which provide no restraint to local out-of-plane rotation. The top and bottom
supports provide no clamp-up, but provide some rotational restraint due to the fixture geometry (the slide plates have a squared
geometry and overlap the specimen by 8 mm [0.30 in.]). The fixture is adjustable to accommodate small variations in specimen
length, width and thickness. The top plate and slide plates, which are not directly attached to the lower portion of the fixture, slip
over the top edge of the test specimen. The side plates are sufficiently short to ensure that a gap between the side rails and the top
plate is maintained during the test.
7.2.1 Support Fixture Details—Detailed drawings for manufacturing the support fixture that satisfy the requirements of this test
method are contained in Figs. 3-10. Other fixtures that meet the The fixture shall be constructed of sufficient stiffness and precision
as to satisfy the loading uniformity requirements of this section may be used (for example, Wyoming Test Fixtures, Inc. Model
CU-CI, Boeing BSS-7260 Type II, Airbus AITM 1.0010, SACMA SRM 2R-94).test method. The following general notes apply
to these figures: The fixture shall be constructed of sufficient stiffness and precision as to satisfy the loading uniformity
requirements of this test method. The following general notes apply to these figures:
7.2.1.1 Machine surfaces to a 3.2 [125] surface finish unless otherwise specified.
7.2.1.2 Break all edges.
7.2.1.3 The test fixture shall be made of steel. It may be made of low carbon steel for ambient temperature testing. For non-ambient
environmental conditions, the recommended fixture material is a nonheat-treated ferritic or precipitation hardened stainless steel
(heat treatment for improved durability is acceptable but not required).
NOTE 4—Experience has shown that fixtures may be damaged due to handling in use, thus periodic re-inspection of the fixture dimensions and tolerances
is important.
7.3 Testing Machine—The testing machine shall be in conformance with Practices E4, and shall satisfy the following
requirements:
Other fixtures that meet the requirements of this section may be used (for example, Wyoming Test Fixtures, Inc. Model CU-CI, Boeing BSS-7260 Type II, Airbus AITM
1.0010, SACMA SRM 2R-94). If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive
careful consideration at a meeting of the responsible technical committee, which you may attend.
D7137/D7137M − 23
7.3.1 Testing Machine Configuration—The testing machine shall have both an essentially stationary head and a movable head. A
short loading train and flat end-loading platens shall be used.
7.3.2 Flat Platens—The test machine shall be mounted with well-aligned, fixed (as opposed to spherical seat) flat platens. The
platen surfaces shall be parallel within 0.025 mm [0.001 in.] across the test fixture top plate length of 100 mm [4.0 in.]. If the
platens are not sufficiently hardened, or simply to protect the platen surfaces, a hardened plate (with parallel surfaces) can be
inserted between each end of the fixture and the corresponding platen. The lower platen should be marked to help center the test
fixture between the platens.
7.3.3 Drive Mechanism—The testing machine drive mechanism shall be capable of imparting to the movable head a controlled
velocity with respect to the stationary head. The velocity of the movable head shall be capable of being regulated as specified in
11.5.
7.3.4 Force Indicator—The testing machine force-sensing device shall be capable of indicating the total force being carried by the
test specimen. This device shall be essentially free from inertia-lag at the specified rate of testing and shall indicate the force with
an accuracy over the force range(s) of interest of within 61 % of the indicated value.
7.3.5 Crosshead Displacement Indicator—The testing machine shall be capable of monitoring and recording the crosshead
displacement (stroke) with a precision of at least 61 %. If machine compliance is significant, it is acceptable to measure the
displacement of the movable head using a LVDT or similar device with 61 % precision on displacement.
7.4 Conditioning Chamber—.When conditioning materials at non-laboratory environments, a temperature-/vapor-level controlled
environmental conditioning chamber is required that shall be capable of maintaining the required temperature to within 63°C
[65°F]63 °C [65 °F] and the required relative humidity level to within 63 %. % RH. Chamber conditions shall be monitored
either on an automated continuous basis or on a manual basis at regular intervals.
7.5 Environmental Test Chamber—An environmental test chamber is required for test environments other than ambient testing
laboratory conditions. This chamber shall be capable of maintaining the test specimen and fixture at the required test environment
during the mechanical test. The test temperature shall be maintained within 63°C [65°F]63 °C [65 °F] of the required
temperature, and the temperature. The relative humidity level shall be maintained to within 63 % of the required humidity
level.controlled within the test chamber shall be defined by the test requestor.
7.6 Strain-Indicating Device—Strain measurement of the specimens is recommended, but not required. If strain measurement is
performed, the longitudinal strain should be measured simultaneously at four locations (two locations on opposite faces of the
specimen as shown in Figs. 11 and 12) to aid in ensuring application of pure compressive loading and to detect bending or
buckling, or both, if any. The same type of strain transducer shall be used for all strain measurements on any single specimen. The
gages, surface preparation, and bonding agents should be chosen to provide for optimal performance on the subject material for
the prescribed test environment. Attachment of the strain-indicating device to the specimen shall not cause damage to the specimen
surface.
NOTE 5—Although the compression test may be performed without the use of strain-indicating devices, lack of instrumentation for the damaged specimens
makes the detection of undesirable panel instability much more difficult. For this reason, strain measurement of the test specimens during compressive
loading is recommended.
NOTE 6—Moisture proofing of the strain gage installations on the specimen needs to be done very carefully with multiple layers of protective coatings
(such as microfined wax, high temperature Teflon tape, adhesively-bonded aluminum foil, and room temperature curing vulcanizing (RTV) compound)
before subjecting them to moisture conditioning inside the environmental conditioning chamber. Foil strain gages, protected simply with RTV compound,
are likely to become corroded and unfit for hot-wet testing after approximately 100 days of moisture conditioning.
7.7 Data Acquisition Equipment—Equipment capable of recording force, crosshead displacement, and strain data is required.
7.8 Alignment Plate—If individual test specimens are not instrumented for strain measurement, an instrumented alignment plate
shall be used to align the support fixture. The alignment plate should be equivalent to the test specimens in terms of material, layup,
Vijayaraju, K., Mangalgiri, P. D., and Parida B. K., “Hot-Wet Compression Testing of Impact Damaged Composite Laminates,” Proceedings of the Ninth International
Conference on Fracture (ICF-9), Sydney, Australia, 1997, pp
...