ASTM C1468-00
(Test Method)Standard Test Method for Transthickness Tensile Strength of Continuous Fiber-Reinforced Advanced Ceramics at Ambient Temperature
Standard Test Method for Transthickness Tensile Strength of Continuous Fiber-Reinforced Advanced Ceramics at Ambient Temperature
SCOPE
1.1 This test method covers the determination of transthickness tensile strength (SUT) under monotonic uniaxial loading of continuous fiber-reinforced ceramics (CFCC) at ambient temperature. This test method addresses, but is not restricted to, various suggested test specimen geometries, test fixtures, data collection and reporting procedure. In general, round or square test specimens are tensile tested in the direction normal to the thickness by bonding appropriate hardware to the samples and performing the test. For a Cartesian coordinate system, the x-axis and the y-axis are in the plane of the test specimen. The transthickness direction is normal to the plane and is labeled the z-axis for this test method. For CFCCs, the plane of the test specimen normally contains the larger of the three dimensions and is parallel to the fiber layers for uni-directional, bi-directional, and woven composites. Note that transthickness tensile strength as used in this test method refers to the tensile strength obtained under monotonic uniaxial loading where monotonic refers to a continuous nonstop test rate with no reversals from test initiation to final fracture.
1.2 This test method is intended primarily for use with all advanced ceramic matrix composites with continuous fiber reinforcement: unidirectional (1-D), bidirectional (2-D), woven, and tridirectional (3-D). In addition, this test method also may be used with glass (amorphous) matrix composites with 1-D, 2-D, and 3-D continuous fiber reinforcement. This test method does not address directly discontinuous fiber-reinforced, whisker-reinforced or particulate-reinforced ceramics, although the test methods detailed here may be equally applicable to these composites. It should be noted that 3-D architectures with a high volume fraction of fibers in the " z" direction may be difficult to test successfully.
1.3 Values are in accordance with the International System of Units (SI) and Practice E380.
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. Additional recommendations are provided in and Section .
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Designation: C 1468 – 00
Standard Test Method for
Transthickness Tensile Strength of Continuous Fiber-
Reinforced Advanced Ceramics at Ambient Temperature
This standard is issued under the fixed designation C 1468; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope bility of regulatory limitations prior to use. Additional recom-
mendations are provided in 6.7 and Section 7.
1.1 This test method covers the determination of transthick-
T
ness tensile strength ~S ! under monotonic uniaxial loading of
U
2. Referenced Documents
continuous fiber-reinforced ceramics (CFCC) at ambient tem-
2.1 ASTM Standards:
perature. This test method addresses, but is not restricted to,
C 1145 Terminology on Advanced Ceramics
various suggested test specimen geometries, test fixtures, data
C 1239 Practice for Reporting Uniaxial Strength Data and
collection and reporting procedure. In general, round or square
Estimating Weibull Distribution Parameters for Advanced
test specimens are tensile tested in the direction normal to the
Ceramics
thickness by bonding appropriate hardware to the samples and
C 1275 Test Method for Monotonic Tensile Strength Test-
performing the test. For a Cartesian coordinate system, the
ing of Continuous Fiber-Reinforced Advanced Ceramics
x-axis and the y-axis are in the plane of the test specimen. The
With Solid Rectangular Cross-Section Specimens at Am-
transthickness direction is normal to the plane and is labeled
bient Temperatures
the z-axis for this test method. For CFCCs, the plane of the test
D 3878 Terminology of High-Modulus Reinforcing Fibers
specimen normally contains the larger of the three dimensions
and Their Composites
and is parallel to the fiber layers for uni-directional, bi-
E 4 Practices for Force Verification of Testing Machines
directional, and woven composites. Note that transthickness
E 6 Terminology Relating to Methods of Mechanical Test-
tensile strength as used in this test method refers to the tensile
ing
strength obtained under monotonic uniaxial loading where
E 337 Test Method for Measuring Humidity With a Psy-
monotonic refers to a continuous nonstop test rate with no
chrometer (the Measurement of Wet-and Dry-Bulb Tem-
reversals from test initiation to final fracture.
peratures)
1.2 This test method is intended primarily for use with all
E 380 Practice for Use of International System of Units (SI)
advanced ceramic matrix composites with continuous fiber
(the Modernized Metric System)
reinforcement: unidirectional (1-D), bidirectional (2-D), wo-
E 1012 Practice for Verification of Specimen Alignment
ven, and tridirectional (3-D). In addition, this test method also
Under Tensile Loading
may be used with glass (amorphous) matrix composites with
1-D, 2-D, and 3-D continuous fiber reinforcement. This test
3. Terminology
method does not address directly discontinuous fiber-
3.1 Definitions—The definitions of terms relating to tensile
reinforced, whisker-reinforced or particulate-reinforced ceram-
testingappearinginTerminologyE 6applytothetermsusedin
ics, although the test methods detailed here may be equally
this test method. The definitions of terms relating to advanced
applicable to these composites. It should be noted that 3-D
ceramics appearing in Terminology C 1145 apply to the terms
architectures with a high volume fraction of fibers in the “z”
used in this test method. The definitions of terms relating to
direction may be difficult to test successfully.
fiber-reinforced composites appearing in Terminology D 3878
1.3 Values are in accordance with the International System
applytothetermsusedinthistestmethod.Pertinentdefinitions
of Units (SI) and Practice E 380.
as listed in Practice E 1012,Terminology C 1145,Terminology
1.4 This standard does not purport to address all of the
D 3878, and Terminology E 6 are shown in the following with
safety concerns, if any, associated with its use. It is the
the appropriate source given in brackets. Terms used in
responsibility of the user of this standard to establish appro-
conjunction with this test method are defined as follows:
priate safety and health practices and determine the applica-
Annual Book of ASTM Standards, Vol 15.01.
1 3
This test method is under the jurisdiction of ASTM Committee C28 on Annual Book of ASTM Standards, Vol 15.03.
Advanced Ceramics and is the direct responsibility of Subcommittee C28.07 on Annual Book of ASTM Standards, Vol 03.01.
Ceramic Matrix Composites. Annual Book of ASTM Standards, Vol 11.03.
Current edition approved June 10, 2000. Published October 2000. Discontinued 1997—Replaced by IEEE/ASTM SI-10.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C 1468
3.1.1 advanced ceramic, n—a highly-engineered, high- difficulty in test specimen machining and testing. Improperly
performance predominately nonmetallic, inorganic, ceramic prepared notches can produce nonuniform stress distribution in
material having specific functional attributes. [C 1145] the shear test specimens and can lead to ambiguity of interpre-
3.1.2 bending strain, n—the difference between the strain at tation of strength results. In addition, these shear test speci-
the surface and the axial strain. [E 1012] mensalsorarelyproduceagagesectionthatisinastateofpure
3.1.3 breaking load, n—the load at which fracture occurs, shear. Uniaxially-loaded transthickness tensile strength tests
T
P , is the breaking load in units of N. [E 6]
measure the tensile interlaminar strength ~S !, avoid the
max
U
3.1.4 ceramic matrix composite (CMC), n—a material con- complications listed above, and provide information on me-
sisting of two or more materials (insoluble in one another), in
chanical behavior and strength for a uniformly stressed mate-
which the major, continuous component (matrix component) is rial. The ultimate strength value measured is not a direct
a ceramic, while the secondary component(s) (reinforcing
measure of the matrix strength, but a combination of the
component) may be ceramic, glass-ceramic, glass, metal or strength of the matrix and the level of bonding between the
organic in nature. These components are combined on a
fiber, fiber/matrix interphase, and the matrix.
macroscale to form a useful engineering material possessing 4.3 CFCCs tested in a transthickness tensile test may fail
certain properties or behavior not possessed by the individual
from a single dominant flaw or from a cumulative damage
constituents. [C 1145]
process; therefore, the volume of material subjected to a
3.1.5 continuous fiber-reinforced ceramic matrix composite
uniform tensile stress for a single uniaxially-loaded transthick-
(CFCC), n—aceramicmatrixcompositeinwhichthereinforc-
ness tensile test may be a significant factor in determining the
ing phases consists of continuous filaments, fibers, yarn, or
ultimate strength of CFCCs. The probabilistic nature of the
knitted or woven fabrics. [C 1145]
strength distributions of the brittle matrices of CFCCs requires
3.1.6 gage length, n—the original length [L ] of that
a sufficient number of test specimens at each testing condition
GL
portion of the test specimen over which strain or change of
for statistical analysis and design, with guidelines for test
length is determined. [E 6]
specimen size and sufficient numbers provided in this test
3.1.7 modulus of elasticity, n—the ratio of stress to corre-
method. Studies to determine the exact influence of test
sponding strain below the proportional limit. [E 6] specimen volume on strength distributions for CFCCs have not
3.1.8 percent bending, n—the bending strain times 100
been completed. It should be noted that strengths obtained
divided by the axial strain. [E 1012] using other recommended test specimens with different vol-
3.1.9 tensile strength, n—themaximumtensilestress,which
umes and areas may vary due to these volume differences.
a material is capable of sustaining. Tensile strength is calcu- 4.4 The results of transthickness tensile tests of test speci-
lated from the maximum load during a tension test carried to
mens fabricated to standardized dimensions from a particular
rupture and the original cross-sectional area of the test speci- material, or selected portions of a part, or both, may not totally
men. [E 6]
represent the strength and deformation properties of the entire,
3.2 Definitions of Terms Specific to This Standard: full-size end product or its in-service behavior in different
3.2.1 transthickness, n—the direction parallel to the thick-
environments.
ness, that is, out-of-plane dimension, as identified in 1.1, and
4.5 For quality control purposes, results derived from stan-
also typically normal to the plies for 1-D, 2-D laminate, and
dardized transthickness tensile test specimens may be consid-
woven cloth. For 3-D laminates this direction is typically taken
ered indicative of the response of the material from which they
to be normal to the thickness and associated with the “z”
were taken for given primary processing conditions and
direction.
post-processing heat treatments.
3.2.2 fixturing, n—fixturing is referred to as the device(s)
4.6 The strength of CFCCs is dependent on their inherent
bonded to the test specimen. It is this device(s) that is actually
resistance to fracture, the presence of flaws, or damage
gripped or pinned to the load train. The fixturing transmits the
accumulation processes, or a combination thereof. Analysis of
applied load to the test specimen.
fracture surfaces and fractography, though beyond the scope of
this test method, is highly recommended.
4. Significance and Use
5. Interferences
4.1 This test method may be used for material development,
material comparison, quality assurance, characterization, and 5.1 Test environment (vacuum, inert gas, ambient air, etc.)
design data generation. including moisture content, for example, relative humidity,
4.2 Continuous fiber-reinforced ceramic matrix composites may have an influence on the measured strength. In particular,
generally are characterized by fine grain sized (<50 µm) glass the behavior of materials susceptible to slow crack growth
or ceramic matrices and ceramic fiber reinforcements. CFCCs fracture will be strongly influenced by test environment and
are candidate materials for high-temperature structural appli- testingrate.Testingtoevaluatethemaximumstrengthpotential
cations requiring high degrees of corrosion and oxidation of a material should be conducted in inert environments or at
resistance,wearresistance,andinherentdamagetolerance,that sufficiently rapid testing rates, or both, so as to minimize slow
is, toughness. In addition, continuous fiber-reinforced glass crack growth effects. Conversely, testing can be conducted in
(amorphous) matrix composites are candidate materials for environments and testing modes and rates representative of
similar but possibly less-demanding applications. Although service conditions to evaluate material performance under use
shear test methods are used to evaluate shear interlaminar conditions. When testing is conducted in uncontrolled ambient
strength (t , t ) in advanced ceramics, there is significant air with the intent of evaluating maximum strength potential,
ZX ZY
C 1468
relative humidity, and temperature must be monitored and
reported. Testing at humidity levels >65 % RH is not recom-
mended and any deviations from this recommendation must be
reported.
5.2 Surface and edge preparation of test specimens, al-
though normally not considered a major concern in CFCCs,
can introduce fabrication flaws which may have pronounced
effectsonthemeasuredtransthicknessstrength(1). Machining
damage introduced during test specimen preparation can be
either a random interfering factor in the determination of
strength of pristine material, that is, increased frequency of
surface-initiated fractures compared to volume-initiated frac-
tures, or an inherent part of the strength characteristics.
Universal or standardized test methods of surface and edge
preparation do not exist. It should be understood that final
machining steps may, or may not, negate machining damage
introduced during the initial machining; thus, test specimen
fabrication history may play an important role in the measured
strength distributions and should be reported. In addition, the
nature of fabrication used for certain composites, for example,
chemical vapor infiltration or hot pressing, may require the
FIG. 1 Schematic Diagram of One Possible Apparatus for
testing of test specimens in the as-processed condition.
Conducting a Uniaxially-Loaded Transthickness Tensile Test
5.3 Bending in uniaxial transthickness tensile tests can
cause or promote nonuniform stress distributions with maxi-
mum stresses occurring at the test specimen edge leading to
nonrepresentativefractures.Similarly,fracturefromedgeflaws
may be accentuated or suppressed by the presence of the
nonuniform stresses caused by bending.
NOTE 1—Finite element calculations were performed for the square
cross section test specimen for the loading conditions and test specimen
thickness investigated in reference (1). Stress levels along the four corner
edgeswerefoundtobelowerthantheinterior,exceptforthecornersatthe
bond lines where the stress was slightly higher than the interior. Stress
levels along the sides and interior of the test specimen were found to be
uniform.
6. Apparatus
6.1 Testing Machines—Machines used for transthickness
tensile testing shall conform to the requirements of Practice
E 4. The loads used in determining tensile strength shall be
accurate within 61 % at any load within the selected load
range of the testing machine as defined in Practice E 4. A
schematic showing pertinent features of the transthickness
FIG. 2 Schematic Diagram of a Second Possible Apparatus for
tensile testing apparatus for two possible loading configura-
Conducting a Uniaxially-Loaded Transthickness Tensile Test
tions is shown in Figs. 1 and 2.
6.1.1 Values for transthickness tensile strength can range a
great deal for different types of CFCC. Therefore, it is helpful
6.1.2 Foranytestingapparatus,theloadtrainwillneedtobe
to know an expected strength value in order to properly select
aligned for angularity and concentricity. Alignment of the
a load range. Approximate transthickness tensile strength
testing system will need to be measured and is detailed inA1.1
values (1) for several CFCCs are as follows: porous oxide/
of Test Method C 1275.
oxide compos
...
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