ASTM D8066/D8066M-23

Standard Practice Unnotched Compression Testing of Polymer Matrix Composite Laminates

SIGNIFICANCE AND USE
5.1 This practice provides supplemental instructions for the use of Test Method D6484/D6484M to determine unnotched compressive strength data for material specifications, research and development, material design allowables, and quality assurance. Factors that influence compressive strengths and shall therefore be reported include the following: material, methods of material fabrication, accuracy of lay-up, laminate 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. Composite properties in the test direction that may be obtained from this test method include:  
5.1.1 Unnotched compressive (UNC) strength, Fxunc,  
5.1.2 Ultimate compressive strain,  
5.1.3 Compressive (linear or chord) modulus of elasticity, Ec, and  
5.1.4 Poisson's ratio in compression.  
5.2 This practice provides a compression test method for laminates containing fibers in multiple fiber directions, particularly those combining axial (0 degree) fibers and off-axis (± θ degree) fibers. Other compression strength test methods include SACMA SRM-1 (also known as the modified D695), D3410/D3410M, D5467/D5467M, D6641/D6641M, and D7249/D7249M. The SRM-1 test uses 12.6 mm [0.50 in.] wide specimens, which is only appropriate for unidirectional tape, cross-ply [0/90]ns tape, or small unit-cell-size fabrics (e.g. 3K-70-P). Larger cell-size fabrics (for example, spread-tow 12K fabrics) should be tested with wider specimens. The standard D3410/D3410M and D6641/D6641M test fixtures do permit the use of wider specimens, for example, 25.4 mm [1.0 in.] wide, and thus can be used to test laminates containing both axial and off-axis fibers; however their gage lengths are relatively short. Test Method D5467/D5467M is intended to obtain the compressive strength of unidirectional laminates, but is expensive due to the sandwich beam confi...
SCOPE
1.1 This practice provides instructions for using the Test Method D6484/D6484M open hole compression test fixture to determine unnotched compressive strength of multi-directional laminates. The composite material forms are limited to continuous-fiber reinforced polymer matrix composites in which the laminate is both symmetric and balanced with respect to the test direction. The range of acceptable test laminates and thicknesses are described in 8.2.1.  
1.2 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 equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
1.2.1 Within the text the inch-pound units are shown in brackets.  
1.3 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.  
1.4 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.

General Information

• Status: Published
• Publication Date: 30-Apr-2023
• ICS: 83.140.20 - Laminated sheets
• 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 D6484/D6484M-23 - Standard Test Method for Open-Hole Compressive Strength of Polymer Matrix Composite Laminates
• Effective Date: 01-Sep-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 D7249/D7249M-20 - Standard Test Method for Facesheet Properties of Sandwich Constructions by Long Beam Flexure
• Effective Date: 01-Feb-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 D6507-19 - Standard Practice for Fiber Reinforcement Orientation Codes for Composite Materials
• Effective Date: 15-Oct-2019
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D3878-19 - Standard Terminology for Composite Materials
• 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

Overview

ASTM D8066/D8066M-23 establishes a standardized practice for unnotched compression testing of polymer matrix composite laminates. Developed by ASTM International, this practice ensures consistency in determining the unnotched compressive strength, modulus of elasticity, ultimate compressive strain, and Poisson’s ratio of multidirectional, balanced, and symmetric continuous-fiber reinforced polymer matrix composites. The standard is widely used in material specification, research and development, material design allowables, and quality assurance within the composite materials industry.

By providing detailed instructions for preparation, conditioning, testing, and reporting, ASTM D8066/D8066M-23 helps manufacturers, researchers, and engineers obtain reliable and comparable data, supporting critical decisions in composite materials design and performance validation.

Key Topics

• Test Method Guidance: Supplemental procedures for using the ASTM D6484/D6484M test fixture to assess unnotched compressive properties of composite laminates.
• Material Restrictions: Applicable to continuous-fiber reinforced laminates that are balanced and symmetric with respect to the direction of testing.
• Reporting Influencers: Factors to be documented include:
  • Material type and fabrication method
  • Stacking sequence and laminate thickness
  • Specimen preparation, conditioning, and alignment
  • Testing environment, speed, and duration
  • Void content and reinforcement volume percentage
• Measured Properties:
  • Unnotched compressive strength (Fxunc)
  • Ultimate compressive strain
  • Compressive modulus of elasticity (Ec)
  • Poisson’s ratio under compression
• Specimen Requirements: Geometries and preparation must follow the specified guidelines to ensure accuracy, with a focus on multidirectional fiber orientation.
• Validation: Valid tests require failure within the designated gage section and must check for specimen buckling or excessive bending. Thorough reporting of results, failure modes, and deviations is required.

Applications

• Material Qualification: Used to determine mechanical properties of composite materials for specification and certification in aerospace, automotive, marine, and industrial applications.
• Design Allowables: Supplies essential mechanical property data to inform design decisions and structural performance analysis.
• Quality Assurance: Regularly applied in manufacturing environments to ensure that polymer matrix composites meet required compressive strength and durability standards.
• Research and Development: Supports the development of new composite materials and optimization of existing laminates for better compressive performance.
• Comparative Testing: Enables evaluation and comparison of different composite laminates, fiber orientations, and fabrication methods in a controlled and reproducible manner.

Related Standards

• ASTM D6484/D6484M: Test Method for Open-Hole Compressive Strength of Polymer Matrix Composite Laminates
• ASTM D3410/D3410M: Compressive Properties of Polymer Matrix Composite Materials by Shear Loading
• ASTM D5467/D5467M: Compressive Properties of Unidirectional Polymer Matrix Composite Materials Using a Sandwich Beam
• ASTM D6641/D6641M: Compressive Properties Using a Combined Loading Compression (CLC) Test
• ASTM D7249/D7249M: Testing Facesheet Properties of Sandwich Constructions by Long Beam Flexure
• ASTM D3171: Constituent Content of Composite Materials
• ASTM D792: Density and Specific Gravity of Plastics by Displacement
• ASTM E132: Poisson’s Ratio at Room Temperature

Practical Value

Adhering to ASTM D8066/D8066M-23 promotes reliability and repeatability in unnotched compression testing for polymer matrix composite laminates. By following a uniform procedure, organizations can generate high-confidence data critical for product certification, material development, and structural analysis. The standard also ensures compatibility of results across laboratories and industries, helping advance quality and innovation in composite material applications.

Keywords: composite materials, compression testing, compressive strength, polymer matrix composites, material testing standards, compressive modulus, Poisson’s ratio, ASTM D8066/D8066M

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: D8066/D8066M − 23
Standard Practice
Unnotched Compression Testing of Polymer Matrix
Composite Laminates
This standard is issued under the fixed designation D8066/D8066M; 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 D883 Terminology Relating to Plastics
D3410/D3410M Test Method for Compressive Properties of
1.1 This practice provides instructions for using the Test
Polymer Matrix Composite Materials with Unsupported
Method D6484/D6484M open hole compression test fixture to
Gage Section by Shear Loading
determine unnotched compressive strength of multi-directional
D3171 Test Methods for Constituent Content of Composite
laminates. The composite material forms are limited to
Materials
continuous-fiber reinforced polymer matrix composites in
D3878 Terminology for Composite Materials
which the laminate is both symmetric and balanced with
D5229/D5229M Test Method for Moisture Absorption Prop-
respect to the test direction. The range of acceptable test
erties and Equilibrium Conditioning of Polymer Matrix
laminates and thicknesses are described in 8.2.1.
Composite Materials
1.2 Units—The values stated in either SI units or inch-
D5467/D5467M Test Method for Compressive Properties of
pound units are to be regarded separately as standard. The
Unidirectional Polymer Matrix Composite Materials Us-
values stated in each system are not necessarily exact equiva-
ing a Sandwich Beam
lents; therefore, to ensure conformance with the standard, each
D6484/D6484M Test Method for Open-Hole Compressive
system shall be used independently of the other, and values
Strength of Polymer Matrix Composite Laminates
from the two systems shall not be combined.
D6507 Practice for Fiber Reinforcement Orientation Codes
1.2.1 Within the text the inch-pound units are shown in
for Composite Materials
brackets.
D6641/D6641M Test Method for Compressive Properties of
1.3 This standard does not purport to address all of the
Polymer Matrix Composite Materials Using a Combined
safety concerns, if any, associated with its use. It is the Loading Compression (CLC) Test Fixture
responsibility of the user of this standard to establish appro-
D7249/D7249M Test Method for Facesheet Properties of
priate safety, health and environmental practices and deter-
Sandwich Constructions by Long Beam Flexure
mine the applicability of regulatory limitations prior to use. E6 Terminology Relating to Methods of Mechanical Testing
1.4 This international standard was developed in accor-
E132 Test Method for Poisson’s Ratio at Room Temperature
dance with internationally recognized principles on standard- E177 Practice for Use of the Terms Precision and Bias in
ization established in the Decision on Principles for the
ASTM Test Methods
Development of International Standards, Guides and Recom- E456 Terminology Relating to Quality and Statistics
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
3. Terminology
3.1 Definitions—Terminology D3878 defines terms relating
2. Referenced Documents
to high-modulus fibers and their composites, as well as terms
2.1 ASTM Standards:
relating to structural sandwich constructions. Terminology
D695 Test Method for Compressive Properties of Rigid
D883 defines terms relating to plastics. Terminology E6 defines
Plastics
terms relating to mechanical testing. Terminology E456 and
D792 Test Methods for Density and Specific Gravity (Rela-
Practice E177 define terms relating to statistics. In the event of
tive Density) of Plastics by Displacement
a conflict between terms, Terminology D3878 shall have
precedence over the other standards.
3.2 Definitions of Terms Specific to This Standard—
This test method is under the jurisdiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.05 on
NOTE 1—If the term represents a physical quantity, its analytical
Structural Test Methods.
dimensions are stated immediately following the term (or letter symbol) in
Current edition approved May 1, 2023. Published June 2023. Originally
approved in 2017. Last previous edition approved in 2017 as D8066/D8066M – 17. fundamental dimension form, using the following ASTM International
DOI: 10.1520/D8066_D8066M-23. standard symbology for fundamental dimensions, shown within square
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8066/D8066M − 23
brackets: [M] for mass, [L] for length, [T] for time, [θ] for thermodynamic
5.1.4 Poisson’s ratio in compression.
temperature, and [nd] for non-dimensional quantities. Use of these
5.2 This practice provides a compression test method for
symbols is restricted to analytical dimensions when used with square
laminates containing fibers in multiple fiber directions, particu-
brackets, as the symbols may have other definitions when used without the
brackets.
larly those combining axial (0 degree) fibers and off-axis (6 θ
degree) fibers. Other compression strength test methods in-
3.2.1 nominal value, n—a value, existing in name only,
clude SACMA SRM-1 (also known as the modified D695),
assigned to a measurable property for the purpose of conve-
D3410/D3410M, D5467/D5467M, D6641/D6641M, and
nient designation. Tolerances may be applied to a nominal
D7249/D7249M. The SRM-1 test uses 12.6 mm [0.50 in.] wide
value to define an acceptable range for the property.
specimens, which is only appropriate for unidirectional tape,
3.3 Symbols:
cross-ply [0/90]ns tape, or small unit-cell-size fabrics (e.g.
A—cross-sectional area of a specimen
3K-70-P). Larger cell-size fabrics (for example, spread-tow
B —face-to-face percent bending in specimen
y
12K fabrics) should be tested with wider specimens. The
CV—sample coefficient of variation, in percent
standard D3410/D3410M and D6641/D6641M test fixtures do
c
E —laminate compressive modulus
permit the use of wider specimens, for example, 25.4 mm [1.0
unc
F —ultimate unnotched compressive strength in the test
x
in.] wide, and thus can be used to test laminates containing
direction
both axial and off-axis fibers; however their gage lengths are
h—specimen thickness
relatively short. Test Method D5467/D5467M is intended to
max
P —maximum force carried by test specimen prior to
obtain the compressive strength of unidirectional laminates,
failure
but is expensive due to the sandwich beam configuration. Test
P —load at ɛ
1 x1
Method D7249/D7249M is intended to obtain the compressive
P —load at ɛ
2 x2
strength of sandwich facesheets.
w—specimen width
5.2.1 Advantages of this practice include:
ɛ —actual measured axial strain value nearest lower end of
x1
5.2.1.1 Avoiding the use of tabs, which are typically re-
strain range used
quired with the end-loaded SRM-1 specimen, which are often
ɛ —actual measured axial strain value nearest upper end of
x2
required with the shear loaded Test Method D3410/D3410M
strain range used
specimen, and sometimes required with the Test Method
ɛ —actual measured transverse strain value nearest lower
y1
D6641/D6641M test specimen, in order to obtain valid failure
end of strain range used
modes, and
ɛ —actual measured transverse strain value nearest upper
y2
5.2.1.2 Longer and wider gage section imposing less con-
end of strain range used
straint on in-plane transverse displacement.
ɛ —indicated axial strain from Gage 1 (used in % bending
xg1
5.2.2 Disadvantages of this practice include:
equation)
5.2.2.1 Longer and wider specimen, thus consuming more
ɛ —indicated axial strain from Gage 2 (used in % bending
xg2
material than other standards noted above
equation)
c
v —Compressive Poisson’s ratio
xy
6. Interferences
4. Summary of Practice
6.1 Environment—Results are affected by the environmental
conditions under which the tests are conducted. Laminates
4.1 In accordance with Test Method D6484/D6484M, per-
tested in various environments can exhibit significant differ-
form a uniaxial compression test of a balanced, symmetric
ences in both failure force and failure mode. Experience has
laminate without a hole.
demonstrated that elevated temperature, humid environments
5. Significance and Use
are generally critical for compressive strength. However,
critical environments must be assessed independently for each
5.1 This practice provides supplemental instructions for the
material system and stacking sequence tested.
use of Test Method D6484/D6484M to determine unnotched
compressive strength data for material specifications, research
6.2 Material Orthotropy—The degree of laminate orthot-
and development, material design allowables, and quality
ropy strongly affects the failure mode and measured strengths.
assurance. Factors that influence compressive strengths and
Valid strength results should only be reported when appropriate
shall therefore be reported include the following: material,
failure modes are observed, according to Section 12.
methods of material fabrication, accuracy of lay-up, laminate
6.3 Thickness Scaling—Thick composite structures do not
stacking sequence and overall thickness, specimen preparation,
necessarily fail at the same strengths as thin structures with the
specimen conditioning, environment of testing, specimen
same laminate orientation (that is, strength does not always
alignment and gripping, speed of testing, time at temperature,
scale linearly with thickness). Thus, data gathered using the
void content, and volume percent reinforcement. Composite
test method described in this practice may not translate directly
properties in the test direction that may be obtained from this
into equivalent thick-structure properties.
test method include:
unc
5.1.1 Unnotched compressive (UNC) strength, F , 6.4 Support Fixture—Results are affected by the amount of
x
5.1.2 Ultimate compressive strain, lateral pressure applied to the test specimen by the support
5.1.3 Compressive (linear or chord) modulus of elasticity, fixture. Sources of variation in this lateral pressure include
c
E , and fixture grip surface, fixture bolt torque, hydraulic gripping
D8066/D8066M − 23
pressure, and fixture shimming choices, and should be con- 8.2.1 Stacking Sequence—The standard laminates shall
trolled and reported as required in Section 11, Procedure, and have multidirectional fiber orientations (fibers shall be oriented
Section 14, Report. Testing unnotched specimens in the Test in a minimum of two directions) and balanced and symmetric
Method D6484/D6484M support fixture is very sensitive to stacking sequences. Nominal thickness shall be 4 mm
fixture gaps, tolerances, and alignment; the fixture can become [0.160 in.], with a permissible range of 3 mm to 5 mm
bent due to high unnotched compressive failure forces, there- [0.125 in. to 0.200 in.], inclusive. Fabric laminates containing
fore the fixture dimensions should be periodically checked. satin-type weaves shall have symmetric warp surfaces, unless
The support fixture can inhibit the growth of delamination otherwise specified and noted in the report.
damage by inhibiting out-of-plane deformation, and by reliev-
NOTE 3—Typically, a [45 /–45 /0 /90 ]ns tape or [45 /0 ]ns fabric
i i j k i j
ing force from the specimen via friction effects.
laminate should be selected such that a minimum of 5 % of the fibers lay
in each of the four principal orientations. This laminate design has been
NOTE 2—It has been found for at least one carbon tape material that the
found to yield the highest likelihood of acceptable failure modes. Note
thermal-spray gripping surface on the Test Method D6484/D6484M test
that testing [0 /90 ]ns tape or fabric laminates can result in acceptable
i j
fixture (see Flagnote 2 in Test Method D6484/D6484M Figures 5 to 8) can
failure modes (see also Section 5). Consult Practice D6507 for informa-
lead to premature failures at the ends of the gripped areas, and that smooth
2 tion on fiber orientation codes.
grip surfaces (no thermal spray) yield superior strength results (1).
8.2.2 Specimen Configuration—The test specimen configu-
6.5 Type of Loading—Differences in force versus crosshead
ration shall be in accordance with Test Method D6484/
displacement and force versus extensometer strain response
D6484M. No hole, notch or damage shall be introduced into
may be observed when comparing hydraulic grip-loaded speci-
the specimen.
mens with end-loaded specimens. Hydraulic grip-loaded data
typically exhibit linear behavior at the onset of loading. At high 8.3 Specimen Preparation—Specimens shall be prepared in
force levels, some nonlinear behavior may be observed due to general accordance with Test Method D6484/D6484M, with
grip slippage. End-loaded data typically display some initial the omission of the hole.
nonlinear behavior at low force levels, due to seating of the
9. Calibration
specimen/fixture assembly underneath the load platens, but
then exhibit linear behavior to failure. The use of specimen end
9.1 The accuracy of all measuring equipment shall have
loading is not allowed by this standard for unnotched specimen
certified calibrations that are current at the time of use of the
testing, as it often leads to end brooming/crushing failures in
equipment.
unnotched compression specimens.
10. Conditioning
7. Apparatus
10.1 The recommended pre-test condition is effective mois-
7.1 General Apparatus—General apparatus shall be in ac-
ture equilibrium at a specific relative humidity as established
cordance with Test Method D6484/D6484M.
by Test Method D5229/D5229M; however, if the test requestor
7.2 Strain-Indicating Device—When required by the test
does not explicitly specify a pre-test conditioning environment,
requestor, longitudinal strain shall be either a) simultaneously no conditioning is required and the test specimens may be
measured using strain gages on opposite faces in the center of
tested as prepared.
the specimen (so as to be within the support fixture opening) to
10.2 The pre-test specimen conditioning process, to include
allow for a correction as a result of any bending of the
specified environmental exposure levels and resulting moisture
specimen, b) measured by use of edge mounted extensometers,
content, shall be reported with the test data.
or c) suitable non-contact strain measurement devices. When
NOTE 4—The term moisture, as used in Test Method D5229/D5229M,
Poisson’s ratio is to be determined, the specimen shall be strain
includes not only the vapor of a liquid and its condensate, but the liquid
gaged instrumented to measure strain in the lateral direction
itself in large quantities, as for immersion.
using the same type of transducer. The same type of strain
10.3 If no explicit conditioning process is performed the
transducer shall be used for all strain measurements on any
specimen conditioning process shall be reported as “uncondi-
single coupon. Attachment of the strain-indicating device to the
tioned” and the moisture content as “unknown.”
coupon shall not cause damage to the specimen surface. Refer
to Test Method D3410/D3410M for additional requirements
11. Procedure
for strain measurement on compression specimens.
11.1 Parameters to Be Specified Before Test:
7.3 Data Acquisition Equipment—Equipment capable of
11.1.1 The specimen sampling method, specimen type and
recording force and strain data is required.
geometry, and conditioning travelers (if required).
11.1.2 All other parameters documented in Test Method
8. Sampling and Test Specimens
D6484/D6484M.
8.1 Sampling—shall be in accordance with Test Method
11.2 General Instruction:
D6484/D6484M.
11.2.1 Any deviations
...

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: D8066/D8066M − 17 D8066/D8066M − 23
Standard Practice
Unnotched Compression Testing of Polymer Matrix
Composite Laminates
This standard is issued under the fixed designation D8066/D8066M; 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 practice provides instructions for using the Test Method D6484D6484/D6484M open hole compression test fixture to
determine unnotched compressive strength of multi-directional laminates. The composite material forms are limited to
continuous-fiber reinforced polymer matrix composites in which the laminate is both symmetric and balanced with respect to the
test direction. The range of acceptable test laminates and thicknesses are described in 8.2.1.
1.2 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.
1.2.1 Within the text the inch-pound units are shown in brackets.
1.3 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.
1.4 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:
D695 Test Method for Compressive Properties of Rigid Plastics
D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement
D883 Terminology Relating to Plastics
D3410/D3410M Test Method for Compressive Properties of Polymer Matrix Composite Materials with Unsupported Gage
Section by Shear Loading
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
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 Aug. 1, 2017May 1, 2023. Published September 2017June 2023. Originally approved in 2017. Last previous edition approved in 2017 as
D8066/D8066M – 17. DOI: 10.1520/D8066_D8066M-17.10.1520/D8066_D8066M-23.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8066/D8066M − 23
D5467/D5467M Test Method for Compressive Properties of Unidirectional Polymer Matrix Composite Materials Using a
Sandwich Beam
D6484/D6484M Test Method for Open-Hole Compressive Strength of Polymer Matrix Composite Laminates
D6507 Practice for Fiber Reinforcement Orientation Codes for Composite Materials
D6641/D6641M Test Method for Compressive Properties of Polymer Matrix Composite Materials Using a Combined Loading
Compression (CLC) Test Fixture
D7249/D7249M Test Method for Facesheet Properties of Sandwich Constructions by Long Beam Flexure
E6 Terminology Relating to Methods of Mechanical Testing
E132 Test Method for Poisson’s Ratio at Room Temperature
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
3. Terminology
3.1 Definitions—Terminology D3878 defines terms relating to high-modulus fibers and their composites, as well as terms relating
to structural sandwich constructions. 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—
NOTE 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 International 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.
3.2.1 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.
3.3 Symbols:
A—cross-sectional area of a specimen
B —face-to-face percent bending in specimen
y
CV—sample coefficient of variation, in percent
c
E —laminate compressive modulus
unc
F —ultimate unnotched compressive strength in the test direction
x
h—specimen thickness
max
P —maximum force carried by test specimen prior to failure
P —load at ɛ
1 x1
P —load at ɛ
2 x2
w—specimen width
ɛ —actual measured axial strain value nearest lower end of strain range used
x1
ɛ —actual measured axial strain value nearest upper end of strain range used
x2
ɛ —actual measured transverse strain value nearest lower end of strain range used
y1
ɛ —actual measured transverse strain value nearest upper end of strain range used
y2
ɛ —indicated axial strain from Gage 1 (used in % bending equation)
xg1
ɛ —indicated axial strain from Gage 2 (used in % bending equation)
xg2
c
v —Compressive Poisson’s ratio
xy
4. Summary of Practice
4.1 In accordance with Test Method D6484/D6484M, perform a uniaxial compression test of a balanced, symmetric laminate
without a hole.
5. Significance and Use
5.1 This practice provides supplemental instructions for the use of Test Method D6484/D6484M to determine unnotched
compressive strength data for material specifications, research and development, material design allowables, and quality assurance.
D8066/D8066M − 23
Factors that influence compressive strengths and shall therefore be reported include the following: material, methods of material
fabrication, accuracy of lay-up, laminate 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. Composite properties in the test direction that may be obtained from this test method include:
unc
5.1.1 Unnotched compressive (UNC) strength, F ,
x
5.1.2 Ultimate compressive strain,
c
5.1.3 Compressive (linear or chord) modulus of elasticity, E , and
5.1.4 Poisson’s ratio in compression.
5.2 This practice provides a compression test method for laminates containing fibers in multiple fiber directions, particularly those
combining axial (0 degree) fibers and off-axis (6 θ degree) fibers. Other compression strength test methods include SACMA
SRM-1 (also known as the modified D695), D3410/D3410M, D5467/D5467M, D6641/D6641M, and D7249/D7249M. The
SRM-1 test uses 12.6 mm [0.50 in.] wide specimens, which is only appropriate for unidirectional tape, cross-ply [0/90]ns tape, or
small unit-cell-size fabrics (e.g. 3K-70-P). Larger cell-size fabrics (e.g., (for example, spread-tow 12K fabrics) should be tested
with wider specimens. The standard D3410/D3410M and D6641/D6641M test fixtures do permit the use of wider specimens, e.g.,
for example, 25.4 mm [1.0 in.] wide, and thus can be used to test laminates containing both axial and off-axis fibers; however their
gage lengths are relatively short. Test Method D5467/D5467M is intended to obtain the compressive strength of unidirectional
laminates, but is expensive due to the sandwich beam configuration. Test Method D7249/D7249M is intended to obtain the
compressive strength of sandwich facesheets.
5.2.1 Advantages of this practice include:
5.2.1.1 Avoiding the use of tabs, which are typically required with the end-loaded SRM-1 specimen, which are often required with
the shear loaded Test Method D3410/D3410M specimen, and sometimes required with the Test Method D6641/D6641M test
specimen, in order to obtain valid failure modes, and
5.2.1.2 Longer and wider gage section imposing less constraint on in-plane transverse displacement.
5.2.2 Disadvantages of this practice include:
5.2.2.1 Longer and wider specimen, thus consuming more material than other standards noted above
6. Interferences
6.1 Environment—Results are affected by the environmental conditions under which the tests are conducted. Laminates tested in
various environments can exhibit significant differences in both failure force and failure mode. Experience has demonstrated that
elevated temperature, humid environments are generally critical for compressive strength. However, critical environments must be
assessed independently for each material system and stacking sequence tested.
6.2 Material Orthotropy—The degree of laminate orthotropy strongly affects the failure mode and measured strengths. Valid
strength results should only be reported when appropriate failure modes are observed, according to Section 12.
6.3 Thickness Scaling—Thick composite structures do not necessarily fail at the same strengths as thin structures with the same
laminate orientation (that is, strength does not always scale linearly with thickness). Thus, data gathered using the test method
described in this practice may not translate directly into equivalent thick-structure properties.
6.4 Support Fixture—Results are affected by the amount of lateral pressure applied to the test specimen by the support fixture.
Sources of variation in this lateral pressure include fixture grip surface, fixture bolt torque, hydraulic gripping pressure, and fixture
shimming choices, and should be controlled and reported as required in Section 11, Procedure, and Section 14, Report. Testing
unnotched specimens in the Test Method D6484/D6484M support fixture is very sensitive to fixture gaps, tolerances, and
alignment; the fixture can become bent due to high unnotched compressive failure forces, therefore the fixture dimensions should
be periodically checked. The support fixture can inhibit the growth of delamination damage by inhibiting out-of-plane deformation,
and by relieving force from the specimen via friction effects.
D8066/D8066M − 23
NOTE 2—It has been found for at least one carbon tape material that the thermal-spray gripping surface on the Test Method D6484/D6484M test fixture
(see Flagnote 2 in Test Method D6484/D6484M Figures 5 to 8) can lead to premature failures at the ends of the gripped areas, and that smooth grip
surfaces (no thermal spray) yield superior strength results (1).
6.5 Type of Loading—Differences in force versus crosshead displacement and force versus extensometer strain response may be
observed when comparing hydraulic grip-loaded specimens with end-loaded specimens. Hydraulic grip-loaded data typically
exhibit linear behavior at the onset of loading. At high force levels, some nonlinear behavior may be observed due to grip slippage.
End-loaded data typically display some initial nonlinear behavior at low force levels, due to seating of the specimen/fixture
assembly underneath the load platens, but then exhibit linear behavior to failure. The use of specimen end loading is not allowed
by this standard for unnotched specimen testing, as it often leads to end brooming/crushing failures in unnotched compression
specimens.
7. Apparatus
7.1 General Apparatus—General apparatus shall be in accordance with Test Method D6484/D6484M.
7.2 Strain-Indicating Device—When required by the test requestor, longitudinal strain shall be either a) simultaneously measured
using strain gages on opposite faces in the center of the specimen (so as to be within the support fixture opening) to allow for a
correction as a result of any bending of the specimen, b) measured by use of edge mounted extensometers, or c) suitable
non-contact strain measurement devices. When Poisson’s ratio is to be determined, the specimen shall be strain gaged instrumented
to measure strain in the lateral direction using the same type of transducer. The same type of strain transducer shall be used for
all strain measurements on any single coupon. Attachment of the strain-indicating device to the coupon shall not cause damage
to the specimen surface. Refer to Test Method D3410/D3410M for additional requirements for strain measurement on compression
specimens.
7.3 Data Acquisition Equipment—Equipment capable of recording force and strain data is required.
8. Sampling and Test Specimens
8.1 Sampling—shall be in accordance with Test Method D6484/D6484M.
8.2 Geometry:
8.2.1 Stacking Sequence—The standard laminates shall have multidirectional fiber orientations (fibers shall be oriented in a
minimum of two directions) and balanced and symmetric stacking sequences. Nominal thickness shall be 4 mm [0.160 in.], with
a permissible range of 3 to 5 mm [0.125 to 0.200 in.], 3 mm to 5 mm [0.125 in. to 0.200 in.], inclusive. Fabric laminates containing
satin-type weaves shall have symmetric warp surfaces, unless otherwise specified and noted in the report.
NOTE 3—Typically, a [45 /–45 /0 /90 ]ns tape or [45 /0 ]ns fabric laminate should be selected such that a minimum of 5 % of the fibers lay in each of the
i i j k i j
four principal orientations. This laminate design has been found to yield the highest likelihood of acceptable failure modes. Note that testing [0 /90 ]ns
i j
tape or fabric laminates can result in acceptable failure modes (see also Section 5). Consult Practice D6507 for information on fiber orientation codes.
8.2.2 Specimen Configuration—The test specimen configuration shall be in accordance with Test Method D6484/D6484M. No
hole, notch or damage shall be introduced into the specimen.
8.3 Specimen Preparation—Specimens shall be prepared in general accordance with Test Method D6484/D6484M, with the
omission of the hole.
9. Calibration
9.1 The accuracy of all measuring equipment shall have certified calibrations that are current at the time of use of the equipment.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
D8066/D8066M − 23
10. Conditioning
10.1 The recommended pre-test condition is effective moisture equilibrium at a specific relative humidity as established by Test
Method D5229/D5229M; however, if the test requestor does not explicitly specify a pre-test conditioning environment, no
conditioning is required and the test specimens may be tested as prepared.
10.2 The pre-test specimen conditioning process, to include specified environmental exposure levels and resulting moisture
content, shall be reported with the test data.
NOTE 4—The term moisture, as used in Test Method D5229/D5229M, includes not only the vapor of a liquid and its condensate, but the liquid itself in
large quantities, as for immersion.
10.3 If no explicit conditioning process is performed the specimen conditioning process shall be reported as “unconditioned” and
the moisture content as “unknown.
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