ASTM C1341-00(2005)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: C 1341 – 00 (Reapproved 2005)
Standard Test Method for
Flexural Properties of Continuous Fiber-Reinforced
Advanced Ceramic Composites
This standard is issued under the fixed designation C1341; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope
Section
Scope 1
1.1 This test method covers the determination of flexural
Referenced Documents 2
properties of continuous fiber-reinforced ceramic composites
Terminology 3
Summary of Test Method 4
in the form of rectangular bars formed directly or cut from
Significance and Use 5
sheets, plates, or molded shapes. Three test geometries are
Interferences 6
described as follows:
Apparatus 7
Precautionary Statement 8
1.1.1 Test Geometry I—Athree-point loading system utiliz-
Specimens 9
ing center loading on a simply supported beam.
Procedures 10
1.1.2 Test Geometry IIA—A four-point loading system uti- Calculation of Results 11
Report 12
lizing two load points equally spaced from their adjacent
Precision and Bias 13
support points with a distance between load points of one half
Keywords 14
of the support span. References
CFCC Surface Condition and Finishing A1
1.1.3 Test Geometry IIB—A four-point loading system uti-
Conditions and Issues in Hot Loading of A2
lizing two load points equally spaced from their adjacent
Specimens into Furnaces
support points with a distance between load points of one third Toe Compensation on Stress-Strain A3
Curves
of the support span.
Corrections for Thermal Expansion in A4
1.2 This test method applies primarily to all advanced
Flexural Equations
ceramic matrix composites with continuous fiber reinforce- Example of Test Report X1
ment:uni-directional(1-D),bi-directional(2-D),tri-directional
1.5 The values stated in SI units are to be regarded as the
(3-D),andothercontinuousfiberarchitectures.Inaddition,this
standard in accordance with IEEE/ASTM SI 10.
test method may also be used with glass (amorphous) matrix
1.6 This standard does not purport to address all of the
composites with continuous fiber reinforcement. However,
safety concerns, if any, associated with its use. It is the
flexural strength cannot be determined for those materials that
responsibility of the user of this standard to establish appro-
do not break or fail by tension or compression in the outer
priate safety and health practices and determine the applica-
fibers.Thistestmethoddoesnotdirectlyaddressdiscontinuous
bility of regulatory limitations prior to use.
fiber-reinforced, whisker-reinforced, or particulate-reinforced
ceramics. Those types of ceramic matrix composites are better
2. Referenced Documents
tested in flexure using Test Methods C1161 and C1211.
2.1 ASTM Standards:
1.3 Tests can be performed at ambient temperatures or at
C1145 Terminology of Advanced Ceramics
elevated temperatures. At elevated temperatures, a suitable
C1161 Test Method for Flexural Strength of Advanced
furnace is necessary for heating and holding the specimens at
Ceramics at Ambient Temperature
the desired testing temperatures.
C1211 Test Method for Flexural Strength of Advanced
1.4 This test method includes the following:
Ceramics at Elevated Temperatures
This test method is under the jurisdiction of ASTM Committee C28 on
Advanced Ceramics and is the direct responsibility of Subcommittee C28.07 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Ceramic Matrix Composites. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved June 1, 2005. Published June 2005. Originally Standards volume information, refer to the standard’s Document Summary page on
approved in 1996. Last previous edition approved in 2000 as C1341–00. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C 1341 – 00 (2005)
−2
C1239 Practice for Reporting Uniaxial Data and Estimat- 3.1.5 flexural strength, n [FL ]—measure of the ultimate
ing Weibull Distribution Parameters forAdvanced Ceram- strength of a specified beam in bending. C 1161
ics
3.1.6 four-point- ⁄3 point flexure, n—configuration of flex-
C1292 Test Method for Shear Strength of Continuous uralstrengthtestingwhereaspecimenissymmetricallyloaded
Fiber-Reinforced Advanced Ceramics at Ambient Tem-
at two locations that are situated one third of the overall span
peratures away from the outer two support bearings.
D790 TestMethodsforFlexuralPropertiesofUnreinforced
3.1.7 four-point- ⁄4 point flexure, n—configuration of flex-
andReinforcedPlasticsandElectricalInsulatingMaterials uralstrengthtestingwhereaspecimenissymmetricallyloaded
D2344/D2344M Test Method for Short-Beam Strength of
attwolocationsthataresituatedonequarteroftheoverallspan
PolymerMatrixCompositeMaterialsandTheirLaminates away from the outer two support bearings. C 1161
−2
D3878 Terminology for Composite Materials
3.1.8 fracture strength, n [FL ]—calculated flexural stress
E4 Practices for Force Verification of Testing Machines
at the breaking load.
−2
E6 Terminology Relating to Methods of Mechanical Test-
3.1.9 modulus of elasticity, n [FL ]—ratio of stress to
ing
corresponding strain below the proportional limit. E6
−2
E177 Practice for Use of the Terms Precision and Bias in
3.1.10 proportional limit stress, n [FL ]—greatest stress
ASTM Test Methods
that a material is capable of sustaining without any deviation
E220 Test Method for Calibration of Thermocouples by
from proportionality of stress to strain (Hooke’s law).
Comparison Techniques
3.1.10.1 Discussion—Many experiments have shown that
E337 TestMethodforMeasuredHumiditywithPsychrom-
valuesobservedfortheproportionallimitvarygreatlywiththe
eter (the Measurement of Wet- and Dry-Bulb Tempera-
sensitivity and accuracy of the testing equipment, eccentricity
tures)
of loading, the scale to which the stress-strain diagram is
E691 Practice for Conducting an Interlaboratory Study to
plotted, and other factors. When determination of proportional
Determine the Precision of a Test Method
limit is required, the procedure and sensitivity of the test
IEEE/ASTM SI 10 American National Standard for Use of
equipment shall be specified. E6
the International System of Units (SI): The Modern Metric
3.1.11 slow crack growth, n—subcritical crack growth (ex-
System
tension) that may result from, but is not restricted to, such
mechanisms as environmentally assisted stress corrosion or
3. Terminology
diffusive crack growth.
3.1 Definitions—The definitions of terms relating to flexure
3.1.12 span-to-depth ratio, n [nd]—for a particular speci-
testingappearinginTerminologyE6applytothetermsusedin
men geometry and flexure test configuration, the ratio (L/d)of
this test method. The definitions of terms relating to advanced
theoutersupportspanlength(L)oftheflexuretestspecimento
ceramics appearing in Terminology C1145 apply to the terms
the thickness/depth (d) of specimen (as used and described in
used in this test method. The definitions of terms relating to
Test Methods D790).
fiber-reinforced composites appearing in Terminology D3878
3.1.13 three-point flexure, n—configuration of flexural
applytothetermsusedinthistestmethod.Pertinentdefinitions
strength testing where a specimen is loaded at a location
as listed in Test Method C1161, Test Methods D790, Termi-
midway between two support bearings. C 1161
nologyC1145,TerminologyD3878,andTerminologyE6are
shown in the following with the appropriate source given in
4. Summary of Test Method
brackets. Additional terms used in conjunction with this test
4.1 Abar of rectangular cross section is tested in flexure as
method are also defined in the following.
a beam as in one of the following three load geometries:
3.1.1 advanced ceramic, n—highly engineered, high-
4.1.1 Test Geometry I—Thebarrestsontwosupportsandis
performance, predominately nonmetallic, inorganic, ceramic
loaded by means of a loading roller midway between the
material having specific functional attributes. C 1145
supports (see Fig. 1.)
3.1.2 breaking load, n [F]—load at which fracture occurs.
4.1.2 TestGeometryIIA—Thebarrestsontwosupportsand
(Inthistestmethod,fractureconsistsofbreakageofthetestbar
is loaded at two points (by means of two loading rollers), each
into two or more pieces or a loss of at least 20% of the
an equal distance from the adjacent support point. The inner
maximum load carrying capacity.) E6
loadingpointsaresituatedonequarteroftheoverallspanaway
3.1.3 ceramic matrix composite, n—material consisting of
from the outer two support bearings.The distance between the
two or more materials (insoluble in one another) in which the
loadingrollers(thatis,theloadspan)isonehalfofthesupport
major,continuouscomponent(matrixcomponent)isaceramic,
span (see Fig. 1).
while the secondary component(s) (reinforcing component)
4.1.3 TestGeometryIIB—Thebarrestsontwosupportsand
may be ceramic, glass-ceramic, glass, metal, or organic in
nature. These components are combined on a macroscale to is loaded at two points (by means of two loading rollers),
situated one third of the overall span away from the outer two
form a useful engineering material possessing certain proper-
ties or behavior not possessed by the individual constituents. supportbearings.Thedistancebetweentheloadingrollers(that
is, the load span) is one third of the support span (see Fig. 1).
3.1.4 continuous fiber-reinforced ceramic composite
(CFCC), n—ceramic matrix composite in which the reinforc- 4.2 The specimen is deflected until rupture occurs in the
ing phase consists of a continuous fiber, continuous yarn, or a outer fibers or until there is a 20% decrease from the peak
woven fabric. load.
C 1341 – 00 (2005)
conditionisrequiredforstatisticalanalysis,withguidelinesfor
sufficient numbers provided in 9.7. Studies to determine the
exact influence of specimen volume on strength distributions
for CFCCs are not currently available.
5.4 The four-point loading geometries (Geometries IIAand
IIB) are preferred over the three-point loading geometry
(Geometry I). In four-point loading, a larger portion of the test
specimenissubjectedtothemaximumtensileandcompressive
stresses, as compared to the three-point geometry. If there is a
statistical/Weibull character failure in the particular composite
systembeingtested,thesizeofthemaximumstressregionwill
play a role in determining the mechanical properties. The
four-point geometry may then produce more reliable statistical
data.
5.5 Flexure tests provide information on the strength and
FIG. 1 Flexural Test Geometries deformation of materials under complex flexural stress condi-
tions. In CFCCs nonlinear stress-strain behavior may develop
as the result of cumulative damage processes (for example,
4.3 The flexural properties of the specimen (flexural
matrixcracking,matrix/fiberdebonding,fiberfracture,delami-
strength and strain, fracture strength and strain, modulus of
nation, etc.) which may be influenced by testing mode, testing
elasticity, and stress-strain curves) are calculated from the load
rate, processing effects, or environmental influences. Some of
and deflection using elastic beam equations.
these effects may be consequences of stress corrosion or
subcritical (slow) crack growth which can be minimized by
5. Significance and Use
testing at sufficiently rapid rates as outlined in 10.3 of this test
5.1 This test method is used for material development,
method.
quality control, and material flexural specifications. Although
5.6 Because of geometry effects, the results of flexure tests
flexural test methods are commonly used to determine design
ofspecimensfabricatedtostandardizedtestdimensionsfroma
strengths of monolithic advanced ceramics, the use of flexure
particular material or selected portions of a component, or
test data for determining tensile or compressive properties of
both, cannot be categorically used to define the strength and
CFCC materials is strongly discouraged. The nonuniform
deformationpropertiesoftheentire,full-sizeendproductorits
stress distributions in the flexure specimen, the dissimilar
in-service behavior in different environments. The effects of
mechanical behavior in tension and compression for CFCCs,
size and geometry shall be carefully considered in extrapolat-
low shear strengths of CFCCs, and anisotropy in fiber archi-
ing the test results to other configurations and performance
tecture all lead to ambiguity in using flexure results for CFCC
conditions.
material design data (1-4). Rather, uniaxial-loaded tensile and
5.7 For quality control purposes, results from standardized
compressive tests are recommended for developing CFCC
flexure test specimens may be considered indicative of the
material design data based on a uniformly stressed test condi-
response of the material lot from which they were taken with
tion.
the given primary processing conditions and post-processing
5.2 In this test method, the flexure stress is computed from
heat treatments.
elastic beam theory with the simplifying assumptions that the
5.8 The flexure behavior and strength of a CFCC are
material is homogeneous and linearly elastic. This is valid for
dependentonitsinherentresistancetofracture,thepresenceof
composites where the principal fiber direction is coincident/
fracture sources, or damage accumulation processes or combi-
transverse with the axis of the beam. These assumptions are
nation thereof. Analysis of fracture surfaces and fractography,
necessary to calculate a flexural strength value, but limit the
though beyond the scope of this test method, is highly
application to comparative type testing such as used for
recommended.
material development, quality control, and flexure specifica-
6. Interferences
tions. Such comparative testing requires consistent and stan-
dardized test conditions, that is, specimen geometry/thickness, 6.1 ACFCC material tested in flexure may fail in a variety
strain rates, and atmospheric/test conditions. of distinct fracture modes, depending on the interaction of the
5.3 Unlike monolithic advanced ceramics which fracture nonuniform stress fields in the flexure specimen and the local
catastrophicallyfromasingledominantflaw,CFCCsgenerally mechanical properties. The specimen may fail in tension,
experience “graceful” fracture from a cumulative damage compression, shear, or in a mix of different modes, depending
process. Therefore, the volume of material subjected to a on which mode reaches the critical stress level for failure to
uniform flexural stress may not be as significant a factor in initiate. To obtain a vali
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