ASTM D6873-03
(Practice)Standard Practice for Bearing Fatigue Response of Polymer Matrix Composite Laminates
Standard Practice for Bearing Fatigue Response of Polymer Matrix Composite Laminates
SIGNIFICANCE AND USE
This practice provides supplemental instructions for using Test Method D 5961/D 5961M to obtain bearing fatigue data for material specifications, research and development, material design allowables, and quality assurance. The primary property that results is the fatigue life of the test specimen under a specific loading and environmental condition. Replicate tests may be used to obtain a distribution of fatigue life for specific material types, laminate stacking sequences, environments, and loading conditions. Guidance in statistical analysis of fatigue data, such as determination of linearized stress life (S-N) curves, can be found in Practice E 739.
This practice can be utilized in the study of fatigue damage in a polymer matrix composite bearing specimen. The loss in strength associated with fatigue damage may be determined by discontinuing cyclic loading to obtain the static strength using Test Method D 5961/D 5961M.
Note 2—This practice may be used as a guide to conduct spectrum loading. This information can be useful in the understanding of fatigue behavior of composite structures under spectrum loading conditions, but is not covered in this standard.
Factors that influence bearing fatigue response and shall therefore be reported include the following: material, methods of material fabrication, accuracy of lay-up, laminate stacking sequence and overall thickness, specimen geometry, specimen preparation (especially of the hole), fastener-hole clearance, fastener type, fastener geometry, fastener installation method, fastener torque (if appropriate), countersink depth (if appropriate), specimen conditioning, environment of testing, type of mating material, number of fasteners, type of support fixture, specimen alignment and gripping, test frequency, force (stress) ratio, bearing stress magnitude, void content, and volume percent reinforcement. Properties that result include the following:
5.3.1 Hole elongation versus fatigue life curves for selected be...
SCOPE
1.1 This practice provides instructions for modifying static bearing test methods to determine the fatigue behavior of composite materials subjected to cyclic bearing forces. 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 This practice supplements Test Method D 5961/D 5961M with provisions for testing specimens under cyclic loading. Several important test specimen parameters (for example, fastener selection, fastener installation method, and fatigue force/stress ratio) are not mandated by this practice; however, repeatable results require that these parameters be specified and reported.
1.3 This practice is limited to test specimens subjected to constant amplitude uniaxial loading, where the machine is controlled so that the test specimen is subjected to repetitive constant amplitude force (stress) cycles. Either engineering stress or applied force may be used as a constant amplitude fatigue variable. The repetitive loadings may be tensile, compressive, or reversed, depending upon the test specimen and procedure utilized.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.5 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
Designation: D 6873 – 03
Standard Practice for
Bearing Fatigue Response of Polymer Matrix Composite
Laminates
This standard is issued under the fixed designation D6873; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This practice provides instructions for modifying static 2.1 ASTM Standards:
bearing test methods to determine the fatigue behavior of D883 Terminology Relating to Plastics
composite materials subjected to cyclic bearing forces. The D3878 Terminology for Composite Materials
composite material forms are limited to continuous-fiber rein- D5229/D5229M Test Method for Moisture Absorption
forced polymer matrix composites in which the laminate is Properties and Equilibrium Conditioning of Polymer Ma-
both symmetric and balanced with respect to the test direction. trix Composite Materials
The range of acceptable test laminates and thicknesses are D5961/D5961M Test Method for Bearing Response of
described in 8.2. Polymer Matrix Composite Laminates
1.2 This practice supplements Test Method D 5961/ E4 Practices for Force Verification of Testing Machines
D5961MD5961/D5961M with provisions for testing speci- E6 Terminology Relating to Methods of Mechanical Test-
mens under cyclic loading. Several important test specimen ing
parameters (for example, fastener selection, fastener installa- E122 Practice for Calculating Sample Size to Estimate,
tionmethod,andfatigueforce/stressratio)arenotmandatedby with a Specified Tolerable Error, the Average for Charac-
this practice; however, repeatable results require that these teristic of a Lot or Process
parameters be specified and reported. E177 Practice for Use of the Terms Precision and Bias in
1.3 This practice is limited to test specimens subjected to ASTM Test Methods
constant amplitude uniaxial loading, where the machine is E456 Terminology Relating to Quality and Statistics
controlled so that the test specimen is subjected to repetitive E467 Practice for Verification of Constant Amplitude Dy-
constant amplitude force (stress) cycles. Either engineering namic Forces in an Axial Fatigue Testing System
stress or applied force may be used as a constant amplitude E739 Practice for Statistical Analysis of Linear or Linear-
fatigue variable. The repetitive loadings may be tensile, com- ized Stress-Life (S-N) and Strain-Life (e-N) Fatigue Data
pressive, or reversed, depending upon the test specimen and E 1309 Guide for Identification of Fiber-Reinforced
procedure utilized. Polymer-Matrix Composite Materials in Databases
1.4 The values stated in either SI units or inch-pound units E1434 GuideforRecordingMechanicalTestDataofFiber-
are to be regarded separately as standard. Within the text the Reinforced Composite Materials in Databases
inch-pound units are shown in brackets. The values stated in E1823 Terminology Relating to Fatigue and Fracture Test-
each system are not exact equivalents; therefore, each system ing
must be used independently of the other. Combining values
3. Terminology
from the two systems may result in nonconformance with the
standard. 3.1 Definitions—Terminology D3878D3878 defines terms
relating to high-modulus fibers and their composites. Termi-
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the nology D883D883 defines terms relating to plastics. Termi-
nology E6E6 defines terms relating to mechanical testing.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- Terminology E1823E1823 defines terms relating to fatigue.
Terminology E456E456 and Practice E177E177 define
bility of regulatory limitations prior to use.
1 2
This practice is under the jurisdiction ofASTM Committee D30 on Composite Annual Book of ASTM Standards, Vol 08.01.
MaterialsandisthedirectresponsibilityofSubcommitteeD30.05onStructuralTest Annual Book of ASTM Standards, Vol 15.03.
Methods. Annual Book of ASTM Standards, Vol 03.01.
Current edition approved March 10, 2003. Published April 2003. 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.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
D6873–03
terms relating to statistics. In the event of a conflict between
h = specimen thickness
terms,Terminology D3878D3878 shall have precedence over
k = calculation factor used in bearing equations to
the other standards.
distinguish single-fastener tests from double-
fastener tests
NOTE 1—If the term represents a physical quantity, its analytical
L = extensometer gage length
g
dimensionsarestatedimmediatelyfollowingtheterm(orlettersymbol)in
N = number of constant amplitude cycles
fundamental dimension form, using the following ASTM standard sym-
P = force carried by specimen
bology for fundamental dimensions, shown within square brackets: [M]
d = crosshead translation
for mass, [L] for length, [T] for time, [u] for thermodynamic temperature,
and[nd]fornon-dimensionalquantities.Useofthesesymbolsisrestricted D = hole elongation
alt
to analytical dimensions when used with square brackets, as the symbols s = alternating bearing stress during fatigue loading
brm
may have other definitions when used without the brackets.
s = maximum cyclic bearing stress magnitude, given
max
by the greater of the absolute values of s and
3.2 Definitions of Terms Specific to This Standard:
min
-2
s
3.2.1 bearing force, P[MLT ], n—thetotalforcecarriedby
max
s = valueofstresscorrespondingtothepeakvalueof
a bearing coupon.
force (stress) under constant amplitude loading
3.2.2 constant amplitude loading, n—in fatigue, a loading
maxq
s = valueofstresscorrespondingtothepeakvalueof
in which all of the peak values of force (stress) are equal and
force (stress) under quasi-static loading for mea-
all of the valley values of force (stress) are equal.
surement of hole elongation, given by the greater
3.2.3 fatigue loading transition, n—in the beginning of
max min
of the absolute values of s and 0.5 3s
fatigue loading, the number of cycles before the force (stress)
mean
s = mean bearing stress during fatigue loading
reaches the desired peak and valley values.
min
s = value of stress corresponding to the valley value
3.2.4 force (stress) ratio, R [nd], n—in fatigue loading, the
offorce(stress)underconstantamplitudeloading
ratio of the minimum applied force (stress) to the maximum
minq
s = value of stress corresponding to the valley value
applied force (stress).
of force (stress) under quasi-static loading for
-1
3.2.5 frequency, f [T ], n—in fatigue loading, the number
measurement of hole elongation, given by the
of force (stress) cycles completed in 1 s (Hz).
min
greater of the absolute values of s and 0.5 3
3.2.6 hole elongation, D [L], n—the permanent change in
max
s
hole diameter in a bearing coupon caused by damage forma-
tion, equal to the difference between the hole diameter in the
4. Summary of Practice
directionofthebearingforceafteraprescribedloadingandthe
hole diameter prior to loading. 4.1 In accordance with Test Method D 5961/
3.2.7 nominal value, n—a value, existing in name only, D5961MD5961/D5961M, but under constant amplitude fa-
assigned to a measurable property for the purpose of conve-
tigue loading, perform a uniaxial test of a bearing specimen.
nient designation. Tolerances may be applied to a nominal Cycle the specimen between minimum and maximum axial
value to define an acceptable range for the property.
forces (stresses) at a specified frequency. At selected cyclic
3.2.8 peak, n—in fatigue loading, the occurrence where the
intervals, determine the hole elongation either through direct
first derivative of the force (stress) versus time changes from
measurementorfromaforce(stress)versusdeformationcurve
positive to negative sign; the point of maximum force (stress)
obtained by quasi-statically loading the specimen through one
in constant amplitude loading.
tension-compression cycle. Determine the number of force
-1 -2
3.2.9 residual strength, [ML T ], n—the value of force
cycles at which failure occurs, or at which a predetermined
(stress) required to cause failure of a specimen under quasi-
hole elongation is achieved, for a specimen subjected to a
static loading conditions after the specimen is subjected to
specific force (stress) ratio and bearing stress magnitude.
fatigue loading.
3.2.10 run-out, n—in fatigue, an upper limit on the number
5. Significance and Use
of force cycles to be applied.
5.1 This practice provides supplemental instructions for
3.2.11 spectrum loading, n—in fatigue, a loading in which
using Test Method D5961/D5961MD5961/D5961M to ob-
the peak values of force (stress) are not equal or the valley
tain bearing fatigue data for material specifications, research
values of force (stress) are not equal (also known as variable
and development, material design allowables, and quality
amplitude loading or irregular loading).
assurance. The primary property that results is the fatigue life
3.2.12 valley, n—in fatigue loading, the occurrence where
ofthetestspecimenunderaspecificloadingandenvironmental
the first derivative of the force (stress) versus time changes
condition. Replicate tests may be used to obtain a distribution
from negative to positive sign; the point of minimum force
of fatigue life for specific material types, laminate stacking
(stress) in constant amplitude loading.
sequences, environments, and loading conditions. Guidance in
3.2.13 wave form, n—the shape of the peak-to-peak varia-
statistical analysis of fatigue data, such as determination of
tion of the force (stress) as a function of time.
linearized stress life (S-N) curves, can be found in Practice
3.3 Symbols:
E739E739.
5.2 This practice can be utilized in the study of fatigue
d = fastener or pin diameter
damage in a polymer matrix composite bearing specimen. The
D = specimen hole diameter
loss in strength associated with fatigue damage may be
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
D6873–03
determined by discontinuing cyclic loading to obtain the static loading. Experience has demonstrated that non-reversed force
strength using Test Method D 5961/D 5961MD 5961/ ratios (especially compression-compression force ratios) ex-
D5961M. hibit greater debris buildup than reversed force ratios, and that
hole elongation can be most accurately determined if debris is
NOTE 2—This practice may be used as a guide to conduct spectrum
removed prior to hole elongation measurement (1,2,4). There-
loading. This information can be useful in the understanding of fatigue
fore, cleaning the specimen hole(s) prior to measurement is
behaviorofcompositestructuresunderspectrumloadingconditions,butis
recommended to ensure conservatism of hole elongation data.
not covered in this standard.
6.4 Environment—Results are affected by the environmen-
5.3 Factorsthatinfluencebearingfatigueresponseandshall
tal conditions under which the tests are conducted. Laminates
therefore be reported include the following: material, methods
tested in various environments can exhibit significant differ-
of material fabrication, accuracy of lay-up, laminate stacking
ences in both hole elongation behavior and failure mode.
sequence and overall thickness, specimen geometry, specimen
Experience has demonstrated that elevated temperature, humid
preparation (especially of the hole), fastener-hole clearance,
environments are generally critical for bearing fatigue-induced
fastener type, fastener geometry, fastener installation method,
hole elongation (1-4). However, critical environments must be
fastener torque (if appropriate), countersink depth (if appropri-
assessed independently for each material system, stacking
ate), specimen conditioning, environment of testing, type of
sequence, and torque condition tested.
mating material, number of fasteners, type of support fixture,
specimen alignment and gripping, test frequency, force (stress) 6.5 Fastener-Hole Clearance—Bearing fatigue test results
ratio, bearing stress magnitude, void content, and volume are affected by the clearance arising from the difference
percent reinforcement. Properties that result include the fol- between hole and fastener diameters. Small changes in clear-
lowing: ancecanchangethenumberofcyclesatwhichholeelongation
5.3.1 Hole elongation versus fatigue life curves for selected initiates, and can affect damage propagation behavior (1). For
bearing stress values. this reason, both the hole and fastener diameters must be
5.3.2 Bearing stress versus hole elongation curves at se- accurately measured and recorded. A typical aerospace toler-
lected cyclic intervals. ance on fastener-hole clearance is +75/-0 µm [+0.003/-0.000
5.3.3 Bearing stress versus fatigue life curves for selected in.] for structural fastener holes.
hole elongation values.
6.6 Fastener Type/Hole Preparation—Results are affected
by the geometry and type of fastener utilized (for example,
6. Interferences
lockbolt, blind bolt) and the fastener installation procedures.
6.1 Force (Stress) Ratio—Results are affected by the force
Results are also affected by the hole preparation procedures.
(stress) ratio under which the tests are conducted. Specimens
6.7 Method of Hole Elongation Measurement—Results are
loaded under tension-tension or compression-compression
affected by the method used to monitor hole elongation. Direct
force (stress) ratios develop hole elongation damage on one
measurement permits an accurate examination of the extent of
side of the fastener hole, whereas specimens loaded under
damage and elongation local to the hole surface. However, the
tension-compression force (stress) ratios can develop damage
measuredelongationmaynotbeuniformthroughthethickness
onbothsidesofthefastenerhole.Experiencehasdemonstrated
of the laminate and may be uneven along the surface of the
that reversed (tension-compression) force ratios are critical for
hole. Additionally, fasteners such as blind bolts and lockbolts
bearing fatigue-induced hole elongation, with fully reversed
are not practical to remove during fatigue testing; use of such
tension-compression (R = −1) being the most critical force
...
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