ASTM D3479/D3479M-96(2002)e1
(Test Method)Standard Test Method for Tension-Tension Fatigue of Polymer Matrix Composite Materials
Standard Test Method for Tension-Tension Fatigue of Polymer Matrix Composite Materials
SCOPE
1.1 This test method determines the fatigue behavior of polymer matrix composite materials subjected to tensile cyclic loading. The composite material forms are limited to continuous-fiber or discontinuous-fiber reinforced composites for which the elastic properties are specially orthotropic with respect to the test direction. This test method is limited to unnotched test specimens subjected to constant amplitude uniaxial in-plane loading where the loading is defined in terms of a test control parameter.
1.2 This test method presents two procedures where each defines a different test control parameter.
1.2.1 Procedure A—A system in which the test control parameter is the load (stress) and the machine is controlled so that the test specimen is subjected to repetitive constant amplitude load cycles. In this procedure, the test control parameter may be described using either engineering stress or applied load as a constant amplitude fatigue variable.
1.2.2 Procedure B—A system in which the test control parameter is the strain in the loading direction and the machine is controlled so that the test specimen is subjected to repetitive constant amplitude strain cycles. In this procedure, the test control parameter may be described using engineering strain in the loading direction as a constant amplitude fatigue variable.
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in non-conformance with this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D3479/D3479M–96 (Reapproved 2002)
Standard Test Method for
Tension-Tension Fatigue of Polymer Matrix Composite
Materials
This standard is issued under the fixed designation D3479/D3479M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
e NOTE—Sections 2.1 and 3.1 were revised editorially in October 2002.
1. Scope priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.1 This test method determines the fatigue behavior of
polymer matrix composite materials subjected to tensile cyclic
2. Referenced Documents
loading. The composite material forms are limited to
2.1 ASTM Standards:
continuous-fiber or discontinuous-fiber reinforced composites
D883 Terminology Relating to Plastics
for which the elastic properties are specially orthotropic with
D3039/D3039M Test Method for Tensile Properties of
respect to the test direction. This test method is limited to
Polymer Matrix Composite Materials
unnotched test specimens subjected to constant amplitude
D3878 Terminology for Composite Materials
uniaxial in-plane loading where the loading is defined in terms
D5229/D5229M Test Method for Moisture Absorption
of a test control parameter.
Properties and Equilibrium Conditioning of Polymer Ma-
1.2 This test method presents two procedures where each
trix Composite Materials
defines a different test control parameter.
E4 Practices for Force Verification of Testing Machines
1.2.1 Procedure A—A system in which the test control
E6 Terminology Relating to Methods of Mechanical Test-
parameter is the load (stress) and the machine is controlled so
ing
that the test specimen is subjected to repetitive constant
E83 Practice for Verification and Classification of Exten-
amplitude load cycles. In this procedure, the test control
someters
parameter may be described using either engineering stress or
E122 Practice for Calculating Sample Size to Estimate,
applied load as a constant amplitude fatigue variable.
With a Specified Tolerable Error, the Average for a
1.2.2 Procedure B—A system in which the test control
Characteristic of a Lot or Process
parameteristhestrainintheloadingdirectionandthemachine
E177 Practice for Use of the Terms Precision and Bias in
is controlled so that the test specimen is subjected to repetitive
ASTM Test Methods
constant amplitude strain cycles. In this procedure, the test
E456 Terminology for Relating to Quality and Statistics
controlparametermaybedescribedusingengineeringstrainin
E467 Practice for Verification of Constant Amplitude Dy-
the loading direction as a constant amplitude fatigue variable.
namic Loads on Displacements in an Axial Load Fatigue
1.3 The values stated in either SI units or inch-pound units
Testing System
are to be regarded separately as standard. Within the text the
E739 Practice for Statistical Analysis of Linear or Linear-
inch-pound units are shown in brackets. The values stated in
ized Stress-Life (S-N) and Strain-Life (e-N) Fatigue Data
each system are not exact equivalents; therefore, each system
E1012 Practice for Verification of Specimen Alignment
must be used independently of the other. Combining values
Under Tensile Loading
from the two systems may result in non-conformance with this
E1049 Practices for Cycle Counting in Fatigue Analysis
standard.
E1823 Terminology Relating to Fatigue and Fracture Test-
1.4 This standard does not purport to address all of the
ing
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
This test method is under the jurisdiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.04 on Annual Book of ASTM Standards, Vol 08.01.
Lamina and Laminate Test Methods. Annual Book of ASTM Standards, Vol 15.03.
Current edition approved June 10, 1996. Published August 1996. Originally Annual Book of ASTM Standards, Vol 03.01.
published as D3479–76. Last previous edition D3479–76. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D3479/D3479M–96 (2002)
3. Terminology 3.3.1 S (or e )—the value of stress (or strain) corre-
max max
sponding to the peak value of the test control parameter in a
3.1 Definitions—TerminologyD3878definestermsrelating
constant amplitude loading.
to high-modulus fibers and their composites. Terminology
3.3.2 S (or e )—the value of stress (or strain) corre-
min min
E1823 defines terms relating to fatigue. Terminology D883
sponding to the valley value of the test control parameter in a
defines terms relating to plastics. Terminology E6 defines
constant amplitude loading.
terms relating to mechanical testing. Terminology E456 and
3.3.3 S (or e )—the mean value of stress (or strain) as
PracticeE177definetermsrelatingtostatistics.Intheeventof mn mn
illustrated in Fig. 1 and given by S =(S + S )/2 or
a conflict between terms, Terminology D3878 shall have mn max min
e =(e + e )/2.
precedence over the other standards. max min
mn
3.3.4 S (or e )—the difference between the mean value of
3.2 Definitions of Terms Specific to This Standard: The a a
stress (or strain) and the maximum and minimum stress (or
following definitions shall have precedence over Terminology
strain) as illustrated in Figure 1 and given by S =(S −
D3878 and over other standards. a max
S )/2 or e =(e − e )/2.
min a max min
3.2.1 constant amplitude loading, n—in fatigue, a loading
3.3.5 N—the scalar value of fatigue life or number of
f
inwhichallofthepeakvaluesofthetestcontrolparameterare
constant amplitude cycles to failure.
equal and all of the valley values of the test control parameter
3.3.6 a—Weibull fatigue life scale parameter.
are equal.
3.3.7 b—Weibull fatigue life shape parameter.
3.2.2 fatigue loading transition, n—in the beginning of
fatigue loading, the number of cycles before the test control
4. Summary of Test Method
parameter reaches the desired peak and valley values.
−1
3.2.3 frequency, f [T ], n—in fatigue loading, the number
4.1 The tensile specimen described in Test Method D3039/
of load (stress) or strain cycles completed in 1 s (Hz). D3039M is mounted in the grips of the testing machine and is
tested as follows:
3.2.4 load (stress) ratio, R [nd], n—in fatigue loading, the
ratio of the minimum applied load (stress) to the maximum 4.1.1 Procedure A—The specimen is cycled between mini-
applied load (stress). mum and maximum in-plane axial load (stress) at a specified
frequency. The number of load cycles at which failure occurs
3.2.5 peak, n—in fatigue loading, the occurrence where the
(or at which a predetermined change in specimen stiffness is
first derivative of the test control parameter versus time
observed) can be determined for a specimen subjected to a
changes from positive to negative sign; the point of maximum
specific load (stress) ratio and maximum stress. For some
load (stress) or strain in constant amplitude loading.
purposes it is useful to obtain the in-plane stiffness at selected
3.2.6 replicate (repeat) tests, n—nominally identical tests
cycle intervals from static axial stress-strain curves using
on different test specimens conducted at the same nominal
modulus determination procedures found in Test Method
value of the independent variable.
D3039/D3039M.
−2
3.2.7 residual stiffness, [FL ], n—the value of modulus of
4.1.2 Procedure B—The specimen is cycled between mini-
a specimen under quasi-static loading conditions after the
mum and maximum in-plane axial strain at a specified fre-
specimen is subjected to fatigue loading.
quency.The number of strain cycles at which specimen failure
−2
3.2.8 residual strength, [FL ], n—thevalueofload(stress)
occurs (or at which a predetermined change in specimen
required to cause failure of a specimen under quasi-static
stiffness is observed) can be determined at a given strain ratio
loading conditions after the specimen is subjected to fatigue
and maximum strain. For some purposes it is useful to obtain
loading.
the in-plane stiffness at selected cycle intervals from static
3.2.9 spectrum loading, n—in fatigue, a loading in which
axial stress-strain curves using modulus determination proce-
the peak values of the test control parameter are not equal or
dures found in Test Method D3039/D3039M or continuously
the valley values of the test control parameter are not equal
from dynamic axial stress-strain data using similar procedures
(also known as variable amplitude loading or irregular load-
as found in Test Method D3039/D3039M.
ing.)
3.2.10 strain ratio, R [nd], n—in fatigue loading, the ratio
e 5. Significance and Use
of the minimum applied strain to the maximum applied strain.
5.1 Thistestmethodisdesignedtoyieldtensilefatiguedata
3.2.11 test control parameter, n—the variable in constant
for material specifications, research and development, quality
amplitude loading whose maximum and minimum values
assurance, and structural design and analysis. The primary test
remain the same during cyclic loading, in other words, load
result is the fatigue life of the test specimen under a specific
(stress) or strain.
loading and environmental condition. Replicate tests may be
3.2.12 valley, n—in fatigue loading, the occurrence where
used to obtain a distribution of fatigue life for specific material
the first derivative of the test control parameter versus time
types, laminate stacking sequences, environments, and loading
changes from negative to positive; the point of minimum load
conditions. Guidance in statistical analysis of fatigue life data,
(stress) or strain in constant amplitude loading.
such as determination of linearized stress life (S-N) or strain-
3.2.13 wave form, n—the shape of the peak-to-peak varia-
life (e-N) curves, can be found in Practice E739.
tion of the test control parameter as a function of time.
5.2 This test method can be utilized in the study of fatigue
3.3 Symbols: damage in a polymer matrix composite such as the occurrence
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D3479/D3479M–96 (2002)
of microscopic cracks, fiber fractures, or delaminations. The Practice E467 and shall be capable of imparting a continuous
specimen’s residual strength or stiffness, or both, may change loadingwaveformtothespecimen.Itisimportanttominimize
due to these damage mechanisms. The loss in stiffness may be drift of the fatigue loading away from the maximum and
quantified by discontinuing cyclic loading at selected cycle minimum values. Achieving such accuracy is critical in the
intervals to obtain the quasi-static axial stress-strain curve development of reliable fatigue life data since small errors in
usingmodulusdeterminationproceduresfoundinTestMethod loading may result in significant errors in fatigue life.
D3039/D3039M. The loss in strength associated with fatigue
7.2.3 Load Indicator—As described in Test Method
damage may be determined by discontinuing cyclic loading to D3039/D3039M. The load indicator shall be in compliance
obtain the static strength usingTest Method D3039/D3039M.
with PracticeE4.The fatigue rating of the load indicator shall
exceed the loads at which testing will take place.Additionally
NOTE 1—This test method may be used as a guide to conduct
this test method recommends compliance with Practice E467
tension-tensionvariableamplitudeloading.Thisinformationcanbeuseful
for the development of a system dynamic conversion for the
in the understanding of fatigue behavior of composite structures under
spectrum loading conditions, but is not covered in this test method. verification of specimen loads to within 1% of true loads.
7.2.4 Strain Indicator—It is recommended that an exten-
6. Interferences
someter be used for strain determination for strain control in
6.1 Material and Specimen Preparation—Poor material
Procedure B, or to obtain strain data for Procedure A. For
fabrication practices, lack of control of fiber alignment, and
specimens to be tested per ProcedureAand to be checked for
damage induced by improper coupon machining are known
initial stiffness only, a bonded strain gage (or gages) may be
causes of a large degree scatter in composite fatigue data.
used for static strain measurements. This test method follows
6.2 System Alignment—Excessive bending will cause pre-
extensometer requirements as found in Test Method D3039/
maturefailure.Everyeffortshouldbemadetoeliminateexcess
D3039M. Verification of data acquisition and extensometer
bending from the test system. Bending may occur due to
accuracy shall be completed in accordance with PracticeE83.
misaligned grips, or from specimens themselves if improperly
However, a static verification is insufficient for dynamic
installed in the grips, or from out-of-tolerance due to poor
loading, and it is recommended as a minimum to conduct a
specimen preparation. If there is any doubt as to the alignment
dynamic verification using Appendix X3 of Practice E83.
inherent in a given test machine then the alignment should be
PracticeE83 discusses dynamic calibration of the extensom-
checked as discussed in 7.2.6.
eter by comparing extensometer strain to those from strain
6.3 Tab Failure—Premature failure of the specimen in the
gages during cyclic loading. Practice E83 discusses the
tab region is common in tension-tension fatigue testing as a
assessment of the vibrational sensitivity of the extensometer
resultofstressconcentrationsinthevicinityoftabregion.Aset
using a single moving anvil.
of preliminary fatigue tests are recommended to find the
NOTE 2—The user is also cautioned that the effect of temperature
combination of tab material, tab length, and adhesive that
variation on strain reading by extensometers may result in erroneous
minimizes tab failures. Using an optical microscope to view
fatigue data as is discussed in PracticeE83.
the edge of the specimen, it can be determined if similar states
7.2.5 Grips—As described in Test Method D 3039/
of damage occur in the tab region and the gage region.
D3039M.Thegripsshallalsohavesufficientfatigueratingfor
6.4 Load History—Variations in testing frequency, and
loads at which testing will take place.
stress (or strain) ratio from test to test will result in variations
infatiguelifedata.Everyeffortshouldbemadetoevaluatethe 7.2.6 System Alignment—Poor system alignment can be a
significant contributor to premature fatigue failure and fatigue
fatigue p
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