ASTM C1275-18

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: C1275 − 18
Standard Test Method for
Monotonic Tensile Behavior of Continuous Fiber-Reinforced
Advanced Ceramics with Solid Rectangular Cross-Section
Test Specimens at Ambient Temperature
This standard is issued under the fixed designation C1275; 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 1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This test method covers the determination of tensile
ization established in the Decision on Principles for the
behavior including tensile strength and stress-strain response
Development of International Standards, Guides and Recom-
under monotonic uniaxial loading of continuous fiber-
mendations issued by the World Trade Organization Technical
reinforcedadvancedceramicsatambienttemperature.Thistest
Barriers to Trade (TBT) Committee.
method addresses, but is not restricted to, various suggested
test specimen geometries as listed in the appendix. In addition,
2. Referenced Documents
test specimen fabrication methods, testing modes (force,
displacement, or strain control), testing rates (force rate, stress
2.1 ASTM Standards:
rate, displacement rate, or strain rate), allowable bending, and
C1145Terminology of Advanced Ceramics
data collection and reporting procedures are addressed. Note
C1239Practice for Reporting Uniaxial Strength Data and
that tensile strength as used in this test method refers to the
EstimatingWeibull Distribution Parameters forAdvanced
tensile strength obtained under monotonic uniaxial loading
Ceramics
where monotonic refers to a continuous nonstop test rate with
D3039/D3039MTestMethodforTensilePropertiesofPoly-
no reversals from test initiation to final fracture.
mer Matrix Composite Materials
1.2 This test method applies primarily to all advanced D3379TestMethodforTensileStrengthandYoung’sModu-
ceramic matrix composites with continuous fiber reinforce- lus for High-Modulus Single-Filament Materials
ment:unidirectional(1D),bidirectional(2D),andtridirectional D3878Terminology for Composite Materials
(3D). In addition, this test method may also be used with glass E4Practices for Force Verification of Testing Machines
(amorphous) matrix composites with 1D, 2D, and 3D continu- E6Terminology Relating to Methods of MechanicalTesting
ous fiber reinforcement. This test method does not directly
E83Practice for Verification and Classification of Exten-
address discontinuous fiber-reinforced, whisker-reinforced, or someter Systems
particulate-reinforced ceramics, although the test methods
E177Practice for Use of the Terms Precision and Bias in
detailed here may be equally applicable to these composites.
ASTM Test Methods
E337Test Method for Measuring Humidity with a Psy-
1.3 Values expressed in this test method are in accordance
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
withtheInternationalSystemofUnits(SI)andIEEE/ASTMSI
peratures)
10.
E691Practice for Conducting an Interlaboratory Study to
1.4 This standard does not purport to address all of the
Determine the Precision of a Test Method
safety concerns, if any, associated with its use. It is the
E1012Practice for Verification of Testing Frame and Speci-
responsibility of the user of this standard to establish appro-
men Alignment Under Tensile and Compressive Axial
priate safety, health, and environmental practices and deter-
Force Application
mine the applicability of regulatory limitations prior to use.
IEEE/ASTM SI 10American National Standard for Use of
Specific hazard statements are given in Section 7 and 8.2.5.2.
theInternationalSystemofUnits(SI):TheModernMetric
System
This test method is under the jurisdiction of ASTM Committee C28 on
Advanced Ceramics and is the direct responsibility of Subcommittee C28.07 on
Ceramic Matrix Composites. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Jan. 1, 2018. Published January 2018. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1994. Last previous edition approved in 2016 as C1275–16. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C1275-18. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1275 − 18
3. Terminology totheproportionallimit,indicatingtheabilityofthematerialto
absorb energy when deformed elastically and return it when
3.1 Definitions:
unloaded.
3.1.1 The definitions of terms relating to tensile testing
–3
3.1.12 modulus of toughness, [FLL ], n—strain energy per
appearing in Terminology E6 apply to the terms used in this
unit volume required to stress the material from zero to final
test method. The definitions of terms relating to advanced
fracture, indicating the ability of the material to absorb energy
ceramics appearing in Terminology C1145 apply to the terms
beyond the elastic range (that is, damage tolerance of the
used in this test method. The definitions of terms relating to
material).
fiber-reinforced composites appearing in Terminology D3878
3.1.12.1 Discussion—Themodulusoftoughnesscanalsobe
applytothetermsusedinthistestmethod.Pertinentdefinitions
referred to as the cumulative damage energy and as such is
as listed in Practice E1012 and Terminologies C1145, D3878,
regardedasanindicationoftheabilityofthematerialtosustain
and E6 are shown in the following with the appropriate source
damage rather than as a material property. Fracture mechanics
given in parentheses. Additional terms used in conjunction
methods for the characterization of CFCCs have not been
with this test method are defined in the following:
developed. The determination of the modulus of toughness as
3.1.2 advanced ceramic, n—highly engineered, high-
provided in this test method for the characterization of the
performance, predominantly nonmetallic, inorganic, ceramic
cumulative damage process in CFCCs may become obsolete
material having specific functional attributes. C1145
when fracture mechanics methods for CFCCs become avail-
3.1.3 axial strain—average longitudinal strains measured at
able.
the surface on opposite sides of the longitudinal axis of
3.1.13 percent bending—bending strain times 100 divided
symmetry of the specimen by two strain-sensing devices
by the axial strain. E1012
located at the mid length of the reduced section. E1012
3.1.14 proportional limit stress—greatest stress that a mate-
3.1.4 bending strain—difference between the strain at the
rial is capable of sustaining without any deviation from
surface and the axial strain. In general, the bending strain
proportionality of stress to strain (Hooke’s law).
variesfrompointtopointaroundandalongthereducedsection
3.1.14.1 Discussion—Many experiments have shown that
of the specimen. E1012
valuesobservedfortheproportionallimitvarygreatlywiththe
3.1.5 breaking force—force at which fracture occurs. E6
sensitivity and accuracy of the testing equipment, eccentricity
of loading, the scale to which the stress-strain diagram is
3.1.6 ceramic matrix composite, n—material consisting of
plotted, and other factors. When determination of proportional
two or more materials (insoluble in one another), in which the
limit is required, the procedure and sensitivity of the test
major,continuouscomponent(matrixcomponent)isaceramic,
equipment should be specified. (See Terminology E6.)
whilethesecondarycomponent/s(reinforcingcomponent)may
be ceramic, glass-ceramic, glass, metal, or organic in nature.
3.1.15 slow crack growth—subcritical crack growth (exten-
These components are combined on a macroscale to form a
sion) which may result from, but is not restricted to, such
useful engineering material possessing certain properties or
mechanisms as environmentally assisted stress corrosion or
behavior not possessed by the individual constituents.
diffusive crack growth.
3.1.7 continuous fiber-reinforced ceramic matrix composite 3.1.16 tensile strength—maximum tensile stress which a
(CFCC), n—ceramic matrix composite in which the reinforc- material is capable of sustaining. Tensile strength is calculated
ing phase consists of a continuous fiber, continuous yarn, or a fromthemaximumloadduringatensiontestcarriedtorupture
woven fabric. and the original cross-sectional area of the specimen. E6
3.1.8 gage length—original length of that portion of the
4. Significance and Use
specimen over which strain or change of length is determined.
4.1 Thistestmethodmaybeusedformaterialdevelopment,
E6
material comparison, quality assurance, characterization, and
–2
3.1.9 matrix-cracking stress, [FL ], n—applied tensile
design data generation.
stress at which the matrix cracks into a series of roughly
4.2 Continuous fiber-reinforced ceramic matrix composites
parallel blocks normal to the tensile stress.
generally characterized by fine grain-sized (<50 µm) matrices
3.1.9.1 Discussion—In some cases, the matrix-cracking
and ceramic fiber reinforcements are candidate materials for
stress may be indicated on the stress-strain curve by deviation
structural applications requiring high degrees of wear and
from linearity (proportional limit) or incremental drops in the
corrosion resistance, and high-temperature inherent damage
stress with increasing strain. In other cases, especially with
tolerance (that is, toughness). In addition, continuous fiber-
materials which do not possess a linear portion of the stress-
reinforced glass (amorphous) matrix composites are candidate
straincurve,thematrix-crackingstressmaybeindicatedasthe
materials for similar but possibly less demanding applications.
first stress at which a permanent offset strain is detected in the
Although flexural test methods are commonly used to evaluate
unloading stress-strain (elastic limit).
strengths of monolithic advanced ceramics, the nonuniform
3.1.10 modulus of elasticity—ratio of stress to correspond-
stress distribution of the flexure specimen in addition to
ing strain below the proportional limit. E6
dissimilar mechanical behavior in tension and compression for
–3
3.1.11 modulus of resilience, [FLL ], n—strain energy per CFCCs lead to ambiguity of interpretation of strength results
unitvolumerequiredtoelasticallystressthematerialfromzero obtained from flexure tests for CFCCs. Uniaxially loaded
C1275 − 18
tensile strength tests provide information on mechanical be- conducted in environments and testing modes and rates repre-
havior and strength for a uniformly stressed material. sentative of service conditions to evaluate material perfor-
mance under use conditions. When testing is conducted in
4.3 Unlike monolithic advanced ceramics which fracture
uncontrolled ambient air with the intent of evaluating maxi-
catastrophicallyfromasingledominantflaw,CFCCsgenerally
mum strength potential, relative humidity and temperature
experience “graceful” fracture from a cumulative damage
must be monitored and reported. Testing at humidity levels
process. Therefore, the volume of material subjected to a
>65% relative humidity (RH) is not recommended and any
uniform tensile stress for a single uniaxially loaded tensile test
deviations from this recommendation must be reported.
may not be as significant a factor in determining the ultimate
strengths of CFCCs. However, the need to test a statistically
5.2 Surface preparation of test specimens, although nor-
significant number of tensile test specimens is not obviated.
mallynotconsideredamajorconcerninCFCCs,canintroduce
Therefore, because of the probabilistic nature of the strength
fabrication flaws that may have pronounced effects on tensile
distributions of the brittle matrices of CFCCs, a sufficient
mechanical properties and behavior (for example, shape and
number of test specimens at each testing condition is required
level of the resulting stress-strain curve, tensile strength and
for statistical analysis and design. Studies to determine the
strain, proportional limit stress and strain, etc.). Machining
exact influence of test specimen volume on strength distribu-
damage introduced during specimen preparation can be either
tions for CFCCs have not been completed. It should be noted
a random interfering factor in the determination of ultimate
that tensile strengths obtained using different recommended
strength of pristine material (that is, increased frequency of
tensile specimens with different volumes of material in the
surface-initiated fractures compared to volume-initiated
gagesectionsmaybedifferentduetothesevolumedifferences.
fractures), or an inherent part of the strength characteristics to
be measured. Surface preparation can also lead to the intro-
4.4 Tensile tests provide information on the strength and
duction of residual stresses. Universal or standardized test
deformation of materials under uniaxial tensile stresses. Uni-
methods of surface preparation do not exist. It should be
form stress states are required to effectively evaluate any
understood that final machining steps may or may not negate
nonlinear stress-strain behavior which may develop as the
machining damage introduced during the initial machining.
result of cumulative damage processes (for example, matrix
Thus, test specimen fabrication history may play an important
cracking, matrix/fiber debonding, fiber fracture, delamination,
role in the measured strength distributions and should be
etc.) which may be influenced by testing mode, testing rate,
reported. In addition, the nature of fabrication used for certain
processing or alloying effects, or environmental influences.
composites (for example, chemical vapor infiltration or hot
Some of these effects may be consequences of stress corrosion
pressing) may require the testing of test specimens in the
or subcritical (slow) crack growth that can be minimized by
as-processed condition (that is, it may not be possible to
testingatsufficientlyrapidratesasoutlinedinthistestmethod.
machine the specimen faces).
4.5 The results of tensile tests of test specimens fabricated
5.3 Bending in uniaxial tensile tests can cause or promote
to standardized dimensions from a particular material or
nonuniform stress distributions with maximum stresses occur-
selected portions of a part, or both, may not totally represent
ring at the test specimen surface, leading to nonrepresentative
the strength and deformation properties of the entire, full-size
fracturesoriginatingatsurfacesorneargeometricaltransitions.
end product or its in-service behavior in different environ-
In addition, if deformations or strains are measured at surfaces
ments.
where maximum or minimum stresses occur, bending may
4.6 For quality control purposes, results derived from stan-
introduce over or under measurement of strains depending on
dardizedtensiletestspecimensmaybeconsideredindicativeof
the location of the strain measuring device on the test speci-
the response of the material from which they were taken for,
men.Similarly,fracturefromsurfaceflawsmaybeaccentuated
given primary processing conditions and post-processing heat
or suppressed by the presence of the nonuniform stresses
treatments.
caused by bending.
4.7 The tensile behavior and strength of a CFCC are
5.4 Fractures that initiate outside the uniformly stressed
dependentonitsinherentresistancetofracture,thepresenceof
gage section of a test specimen may be due to factors such as
flaws, or damage accumulation processes, or both.Analysis of
stress concentrations or geometrical transitions, extraneous
fracturesurfacesandfractography,thoughbeyondthescopeof
stressesintroducedbygripping,orstrength-limitingfeaturesin
this test method, is highly recommended.
the microstructure of the test specimen. Such non-gage section
fractures will normally constitute invalid tests. In addition, for
5. Interferences
face-loaded geometries, gripping pressure is a key variable in
5.1 Test environment (vacuum, inert gas, ambient air, etc.)
the initiation of fracture. Insufficient pressure can shear the
including moisture content (for example, relative humidity)
outer plies in laminated CFCCs, while too much pressure can
may have an influence on the measured tensile strength. In
causelocalcrushingoftheCFCCandfractureinthevicinityof
particular, the behavior of materials susceptible to slow crack
the grips.
growthfracturewillbestronglyinfluencedbytestenvironment
and testing rate. Testing to evaluate the maximum strength
6. Apparatus
potential of a material should be conducted in inert environ-
ments or at sufficiently rapid testing rates, or both, so as to 6.1 Testing Machines—Machines used for tensile testing
minimizeslowcrackgrowtheffects.Conversely,testingcanbe shall conform to the requirements of Practices E4. The force
C1275 − 18
used in determining tensile strength shall be accurate to within
61%atanyforcewithintheselectedforcerangeofthetesting
machine as defined in Practices E4. A schematic showing
pertinent features of the tensile testing apparatus is shown in
Fig. 1.
6.2 Gripping Devices:
6.2.1 General—Various types of gripping devices may be
used to transmit the measured load applied by the testing
machine to the test specimens. The brittle nature of the
FIG. 2 Example of a Direct Lateral Pressure Grip Face for a
matrices of CFCCs requires a uniform interface between the
Face-Loaded Grip Interface
gripcomponentsandthegrippedsectionofthespecimen.Line
or point contacts and nonuniform pressure can produce
Hertizan-typestressesleadingtocrackinitiationandfractureof
the test specimen in the gripped section. Gripping devices can
be classed generally as those employing active and those
employingpassivegripinterfacesasdiscussedinthefollowing
sections.
6.2.2 Active Grip Interfaces—Active grip interfaces require
a continuous application of a mechanical, hydraulic, or pneu-
matic force to transmit the load applied by the test machine to
the test specimen. Generally, these types of grip interfaces
causeaforcetobeappliednormaltothesurfaceofthegripped
section of the specimen. Transmission of the uniaxial force
applied by the test machine is then accomplished by friction
between the test specimen and the grip faces. Thus, important
aspects of active grip interfaces are uniform contact between
the gripped section of the test specimen and the grip faces and
constant coefficient of friction over the grip/specimen inter-
face.
FIG. 3 Example of Indirect Wedge-Type Grip Faces for a Face-
Loaded Grip Interface
6.2.2.1 For flat test specimens, face-loaded grips, either by
directlateralpressuregripfaces (1) orbyindirectwedge-type
grip faces, act as the grip interface (2) as illustrated in Fig. 2
and Fig. 3, respectively. Generally, close tolerances are re-
quired for the flatness and parallelism as well as for the wedge
angle of the wedge grip faces. In addition, the thickness,
flatness, and parallelism of the gripped section of the test
specimen must be within similarly close tolerances to promote
uniform contact at the test specimen/grip interface. Tolerances
willvarydependingontheexactconfigurationasshowninthe
appropriate test specimen drawings.
6.2.2.2 Sufficientlateralpressuremustbeappliedtoprevent
slippage between the grip face and the test specimen. Grip
surfacesthatarescoredorserratedwithapatternsimilartothat
of a single-cut file have been found satisfactory. A fine
serration appears to be the most satisfactory. The serrations
shouldbekeptcleanandwelldefinedbutnotoverlysharp.The
lengthandwidthofthegripfacesshouldbeequaltoorgreater
than the respective length and width of the gripped sections of
the test specimen.
FIG. 1 Schematic Diagram of One Possible Apparatus for Con- The boldface numbers given in parentheses refer to a list of references at the
ducting a Uniaxially Loaded Tensile Test end of the text.
C1275 − 18
6.2.3 Passive Grip Interfaces—Passivegripinterfacestrans- 6.3.1 General—Various types of devices (load train cou-
mit the force applied by the test machine to the test specimen plers)maybeusedtoattachtheactiveorpassivegripinterface
through a direct mechanical link. Generally, these mechanical
assemblies to the testing machine. The load train couplers in
links transmit the test forces to the specimen via geometrical
conjunction with the type of gripping device play major roles
features of the test specimens such as shank shoulders or holes
in the alignment of the load train and thus subsequent bending
in the gripped head.Thus, the important aspect of passive grip
imposed in the specimen. Load train couplers can be classified
interfacesisuniformcontactbetweenthegrippedsectionofthe
generally as fixed and non-fixed as discussed in the following
test specimen and the grip faces.
sections. Note that use of well-aligned fixed or self-aligning
6.2.3.1 For flat test specimens, passive grips may act either
non-fixedcouplersdoesnotautomaticallyguaranteelowbend-
through edge loading via grip interfaces at the shoulders of the
ing in the gage section of the tensile test specimen. Generally,
specimenshank (3)orbycombinationsoffaceloadingandpin
well-aligned fixed or self-aligning non-fixed couplers provide
loading via pins at holes in the gripped specimen head (4, 5).
for well-aligned load trains, but the type and operation of grip
Generally,closetolerancesoflinearandangulardimensionsof
interfacesaswellastheas-fabricateddimensionsofthetensile
shoulder and grip interfaces are required to promote uniform
test specimen can add significantly to the final bending
contact along the entire test specimen/grip interface as well as
imposed in the gage section of the test specimen.
to provide for non-eccentric loading as shown in Fig. 4.In
6.3.1.1 Regardless of which type of coupler is used, align-
addition, moderately close tolerances are required for center
linecoincidenceanddiametersofthepinsandholeasindicated mentofthetestingsystemshallbeverifiedataminimumatthe
in Fig. 5. beginning and end of a test series unless the conditions for
6.2.3.2 When using edge-loaded test specimen, lateral cen-
verifying alignment as detailed in X1.1 are otherwise met. A
tering of the test specimen within the grip attachments is
test series is interpreted to mean a discrete group of tests on
accomplished by use of wedge-type inserts machined to fit
individualtestspecimensconductedwithinadiscreteperiodof
within the grip cavity. In addition, wear of the grip cavity can
time on a particular material configuration, test specimen
bereducedbyuseofthethinbrasssheetsbetweenthegripand
geometry, test conditions, or other uniquely definable qualifier
test specimen without adversely affecting specimen alignment.
(for example, a test series composed of materialAcomprising
6.2.3.3 Thepinsintheface/pin-loadedgripareprimarilyfor
tentestspecimensofgeometryBtestedatafixedrateinstrain
alignment purposes with a secondary role of force transmis-
control to final fracture in ambient air). An additional verifi-
sion. Primary load transmission is through face loading via
cation of alignment is recommended, although not required, at
mechanically actuated wedge grip faces. Proper tightening of
the middle of the test series. Either a dummy or actual test
the wedge grip faces against the test specimen to prevent
specimen and the alignment verification procedures detailed in
slipping but avoid compressive fracture of the test specimen
the appendix must be used. Allowable bending requirements
gripped section must be determined for each material and test
are discussed in 6.5.Tensile test specimens used for alignment
specimen type.
verification should be equipped with a recommended eight
6.2.3.4 Note that passive grips employing single pins in
separate longitudinal strain gages to determine bending contri-
each gripped section of the test specimen as the primary force
butions from both eccentric and angular misalignment of the
transfer mechanism are not recommended. Relatively low
grip heads. Ideally the verification specimen should be of
interfacial shear strengths compared to longitudinal tensile
identical material to that being tested. However, in the case of
strengths in CFCCs (particularly for 1D reinforced materials
CFCCs, the type of reinforcement or degree of residual
loadedalongthefiberdirection)maypromotenon-gagesection
porosity may complicate the consistent and accurate measure-
fractures along interfaces particularly at geometric transitions
or at discontinuities such as holes. ment of strain. Therefore, an alternate material (isotropic,
homogeneous, continuous) with elastic modulus, elastic strain
6.3 Load Train Couplers:
capability, and hardness similar to the test material is recom-
mended.Inaddition,dummytestspecimensusedforalignment
verification should have the same geometry and dimensions of
the actual test specimens, as well as similar mechanical
properties as the test material to ensure similar axial and
bendingstiffnesscharacteristicsastheactualtestspecimenand
material.
6.3.2 Fixed Load Train Couplers—Fixed couplers may
incorporate devices that require either a one-time pre-test
alignment adjustment of the load train which remains constant
for all subsequent tests, or an in situ pre-test alignment of the
load train that is conducted separately for each test specimen
and each test. Such devices (6, 7) usually employ angularity
andconcentricityadjusterstoaccommodateinherentloadtrain
misalignments.Regardlessofwhichmethodisused,alignment
FIG. 4 Example of an Edge-Loaded, Passive Grip Interface (3) verification must be performed as discussed in 6.3.1.1.
C1275 − 18
FIG. 5 Example of Pin/Face-Loaded Passive Grip Interface (4)
6.3.2.1 Fixedloadtraincouplersarepreferredinmonotonic nate the need to evaluate the bending in the test specimen for
testing CFCCs because of the “graceful” fracture process in each test, the operation of the couplers must be verified as
these materials. During this “graceful” fracture process, the discussed in 6.3.1.1.
fixed coupler tends to hold the test specimen in an aligned
6.3.3.1 Non-fixed load train couplers are useful in rapid test
position, and thus, provides a continuous uniform stress across
rate or constant load testing of CFCCs where the “graceful”
the remaining ligament of the gage section.
fracture process is not as apparent. If the material exhibits
6.3.3 Non-Fixed Load Train Couplers—Non-fixed couplers
“graceful” fracture, the self-aligning feature of the non-fixed
may incorporate devices that promote self-alignment of the
coupler will allow rotation of the gripped section of the test
load train during the movement of the crosshead or actuator.
specimen,thuspromotinganonuniformstressintheremaining
Generally, such devices rely upon freely moving linkages to
ligament of the gage section.
eliminate applied moments as the load train components are
6.4 Strain Measurement—Strain should be determined by
loaded.Knifeedges,universaljoints,hydrauliccouplers,orair
means of either a suitable extensometer or strain gages. If
bearings are examples (4, 8, 9) of such devices. Examples of
Poisson’s ratio is to be determined, the test specimen must be
two such devices are shown in Fig. 6.Although non-fixed load
instrumented to measure strain in both longitudinal and lateral
train couplers are intended to be self-aligning and thus elimi-
directions.
6.4.1 Extensometers used for tensile testing of CFCC test
specimens shall satisfy Practice E83, Class B-1 requirements
and are recommended to be used in place of strain gages for
test specimens with gage lengths of ≥25 mm and shall be used
for high-performance tests beyond the range of strain gage
applications. Extensometers shall be calibrated periodically in
accordancewithPracticeE83.Forextensometersmechanically
attachedtothetestspecimen,theattachmentshouldbesuchas
to cause no damage to the test specimen surface. In addition,
the weight of the extensometer should be supported so as not
to introduce bending greater than that allowed in 6.5.
6.4.2 Although not recommended for the actual testing,
strain can also be determined directly from strain gages. If
Poisson’s ratio is to be determined, the test specimen must be
instrumented to measure strain in both longitudinal and lateral
directions.Unlessitcanbeshownthatstraingagereadingsare
not unduly influenced by localized strain events such as fiber
crossovers, strain gages should not be less than 9 to 12 mm in
length for the longitudinal direction and not less than 6 mm in
lengthforthetransversedirection.Notethatlargerstraingages
than those recommended here may be required for fabric
FIG. 6 Examples of Hydraulic, Self-Aligning, Non-Fixed Load
Train Couplers (8, 9) reinforcements to average the localized strain effects of the
C1275 − 18
fiber crossovers. The strain gages, surface preparation, and 6.7 Dimension Measuring Devices—Micrometers and other
bonding agents should be chosen to provide adequate perfor- devices used for measuring linear dimensions should be
mance on the subject materials and suitable strain recording accurate and precise to at least one-half the smallest unit to
equipment should be employed. Note that many CFCCs may whichtheindividualdimensionisrequiredtobemeasured.For
exhibit high degrees of porosity and surface roughness and the purposes of this test method, cross-sectional dimensions
therefore require surface preparation including surface filling should be measured to within 0.02 mm, requiring dimension
before the strain gages can be applied. measuring devices with accuracies of 0.01 mm.
6.5 Allowable Bending—Analytical and empirical studies
7. Hazards
(10)haveconcludedthatfornegligibleeffectsontheestimates
7.1 Duringtheconductofthistestmethod,thepossibilityof
of the strength distribution parameters (for example, Weibull
flying fragments of broken test material is high. The brittle
modulus, mˆ, and characteristic strength, σˆ ) of monolithic
θ
nature of advanced ceramics and the release of strain energy
advanced ceramics, allowable percent bending as defined in
contribute to the potential release of uncontrolled fragments
Practice E1012 should not exceed five.These conclusions (10)
upon fracture. Means for containment and retention of these
assume that tensile strength fractures are due to single fracture
fragments for later fractographic reconstruction and analysis is
origins in the volume of the material, all tensile test specimens
highly recommended.
experienced the same level of bending, and that Weibull
modulus, mˆ, was constant.
7.2 Exposed fibers at the edges of CFCC test specimens
6.5.1 Similar studies of the effect of bending on the tensile
present a hazard due to the sharpness and brittleness of the
strength distributions of CFCCs do not exist. Until such
ceramic fiber. All those required to handle these materials
informationisforthcomingforCFCCs,thistestmethodadopts
should be well informed of such conditions and the proper
the recommendations for tensile testing of monolithic ad-
handling techniques.
vanced ceramics. Therefore, the recommended maximum al-
lowablepercentbendingattheonsetofthecumulativefracture 8. Test Specimens
process (for example, matrix-cracking stress) for test speci-
8.1 Test Specimen Geometry:
mens tested under this test method is five. However, it should
8.1.1 General—The geometry of tensile test specimen is
benotedthatunlessalltestspecimensareproperlystraingaged
dependent on the ultimate use of the tensile strength data. For
and percent bending monitored until the onset of the cumula-
example, if the tensile strength of an as-fabricated component
tivefractureprocess,therewillbenorecordofpercentbending
is required, the dimensions of the resulting tensile test speci-
at the onset of fracture for each test specimen. Therefore, the
menmayreflectthethickness,width,andlengthrestrictionsof
testing system shall be verified using the procedure detailed in
the component. If it is desired to evaluate the effects of
the appendix such that percent bending does not exceed five at
interactions of various constituent materials for a particular
a mean strain equal to either one-half the anticipated strain at
CFCC manufactured via a particular processing route, then the
the onset of the cumulative fracture process (for example,
size of the test specimen and resulting gage section will reflect
matrix-cracking stress) or a strain of 0.0005 (that is, 500
the desired volume to be sampled. In addition, grip interfaces
microstrain), whichever is greater. This verification shall be
and load train couplers as discussed in Section 6 will influence
conducted at a minimum at the beginning and end of each test
the final design of the test specimen geometry.
seriesasrecommendedin6.3.1.1.Anadditionalverificationof
8.1.1.1 The following sections discuss the more common,
alignment is recommended, although not required, at the
and thus proven, of these tensile test specimen geometries,
middle of the test series.
although any geometry is acceptable if it meets the gripping,
6.6 DataAcquisition—Ataminimum,autographicrecordof
fracturelocation,andbendingrequirementsofthistestmethod.
applied load and gage section elongation or strain versus time
Deviations from the recommended geometries may be neces-
shouldbeobtained.Eitheranalogchartrecordersordigitaldata sary depending upon the particular CFCC being evaluated.
acquisition systems can be used for this purpose, although a
Stress analyses of untried test specimens should be conducted
digital record is recommended for ease of later data analysis. to ensure that stress concentrations that can lead to undesired
Ideally, an analog chart recorder or plotter should be used in
fractures outside the gage sections do not exist. It should be
conjunction with the digital data acquisition system to provide notedthatcontouredspecimensbytheirnaturecontaininherent
an immediate record of the test as a supplement to the digital
stressconcentrationsduetogeometrictransitions.Stressanaly-
record. Recording devices shall be accurate to within 60.1% ses can indicate the magnitude of such stress concentrations
for the entire testing system including readout unit as specified
while revealing the success of producing a uniform tensile
inPracticesE4andshallhaveaminimumdataacquisitionrate stress state in the gage section of the test specimen.
of 10 Hz, with a response of 50 Hz deemed more than
8.1.1.2 Generally, test specimens with contoured gage sec-
sufficient. tions (transition radiuses of >50 mm) are preferred to promote
6.6.1 Strain or elongation of the gage section, or both, the tensile stresses with the greatest values in the uniformly
should be recorded either similarly to the force or as indepen- stressed gage section (11) while minimizing the stress concen-
dent variables of force. Crosshead displacement of the test trationduetothegeometricaltransitionoftheradius.However,
machinemayalsoberecordedbutshouldnotbeusedtodefine in certain instances (for example, 1D CFCCs tested along the
displacement or strain in the gage section, especially when directionofthefibers),lowinterfacialshearstrengthrelativeto
self-aligning couplers are used in the load train. the tensile strength in the fiber direction will cause splitting of
C1275 − 18
the test specimen initiating at the transition region between the woven E-glass have proven to be satisfactory for certain
gage section and the gripped section of the test specimen with fiber-reinforced polymers (see Test Method D3039/D3039M).
the split propagating along the fiber direction, leading to For CFCCs, fiberglass-reinforced epoxy, PMR, and carbon
fractureofthetestspecimen.Inthesecases,straight-sided(that fiber-reinforcedresintabmaterialshavebeenusedsuccessfully
is, noncontoured) test specimens as shown in Fig. 7 may be (11). However metallic tabs (for example, aluminum alloys)
required for determining the tensile strength behavior of the may be satisfactory as long as the tabs are strain compatible
CFCC. In other instances, a particular fiber weave or process- (havingasimilarelasticmodulusastheCFCC)withtheCFCC
ing route will preclude fabrication of test specimens with material being tested. Each beveled tab (bevel angle <15°)
reduced gage sections, thus requiring implementation of should be a minimum of 30 mm long, the same width of the
straight-sidedspecimens.Straight-sidedtestspecimensmaybe test specimen, and have the total thickness of the tabs on the
gripped in any of the methods discussed here, although active order of the thickness of the test specimen. Any high-
gripping systems are recommended for minimizing non-gage elongation (tough) adhesive system may be used with the
section fractures. length of the tabs determined by the shear strength of the
8.1.2 Edge-Loaded Flat Tensile Test Specimens—Figs.X2.1 adhesive, size of the test specimen, and estimated strength of
and X2.2 show examples of edge-loaded test specimens which the composite. In any case, a significant fraction (≥20%) of
utilize the lateral compressive stresses developed at the test fractures within one test specimen width of the tab shall be
specimen/grip interface at the gripped section as the test cause to re-examine the tab materials and configuration,
specimen is pulled into the wedge of the grip. This type of gripping method and adhesive, and to make necessary adjust-
geometryhasbeensuccessfullyemployedfortheevaluationof mentstopromotefracturewithinthegagesection.Fig.8shows
1D, 2D, and 3D CFCCs. Of particular concern with this an example of tab design which has been used successfully
geometry is the proper and consistent angle of the edge-loaded with CFCCs (11).
shank as shown in Figs. X2.1 and X2.2.Thus, the edge-loaded 8.1.4 Pin/Face-Loaded Flat Tensile Specimens—The test
geometry may require somewhat intensive fabrication and specimens shown in Figs. X2.6-X2.8 employ combinations of
inspection procedures. pin and face loading to transmit the uniaxial force of the test
8.1.3 Face-Loaded Flat Tensile Test Specimens—Figs. machine to the specimen. Close tolerances of hole/pin diam-
X2.3-X2.5 show examples of face-loaded test specimens that eters and center lines are required to ensure proper test
exploit the friction at the test specimen/grip interface to specimenalignmentinthegripsandtransmissionoftheforces.
transmit the uniaxial force applied by the test machine. Theface-loadedpartofthegeometryprovidestheprimaryload
Important tolerances for the face-loaded geometry include transmission mechanisms in these test specimens. Important
parallelism and flatness of faces, all of which will vary tolerances for the face-loaded part of the geometry include
depending on the exact configuration as shown in the appro- parallelism and flatness of faces, both of which will vary
priate test specimen drawings. depending on the exact configuration as shown in the appro-
8.1.3.1 For face-loaded test specimens, especially for priate test specimen drawings.Thus the pin/face loaded geom-
straight sided (that is, noncontoured) test specimens, end tabs etry may require somewhat intensive fabrication procedures.
may be required to provide a compliant layer for gripping. 8.1.4.1 Note that test specimens requiring single pins in
Balanced 0/90° cross-ply tabs made from unidirectional non- each gripped section of the specimen as the primary force
FIG. 7 Example of Straight-Sided Test Specimen Geometry
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FIG. 8 Example of a Bevelled Tab Successfully Used with Face-Loaded CFCC Tensile Test Specimens (11)
transfer mechanism are not recommended. Relatively low 8.2.5.1 All grinding or cutting should be done with ample
interfacial shear strengths compared to longitudinal tensile supply of appropriate filtered coolant to keep the workpiece
strengths in CFCCs (particularly for 1D reinforced materials and grinding wheel constantly flooded and particles flushed.
loadedalongthefiberdirection)maypromotenon-gagesection Grinding can be done in at least two stages, ranging from
fractures along interfaces particularly at geometric transitions coarse to fine rate of material removal.All cutting can be done
or at discontinuities such as holes. in one stage appropriate for the depth of cut.
8.2.5.2 Stock removal rate should be on the order of
8.2 Test Specimen Preparation:
0.03mm per pass using diamond tools that have between 320
8.2.1 Dependingupontheintendedapplicationofthetensile
and 600 grit. Remove equal stock from each face where
strength data, use one of the following test specimen prepara-
applicable. (Warning—Care should be exercised in storage
tion procedures. Regardless of the preparation procedure used,
and handling of finished test specimens to avoid the introduc-
sufficient details regarding the procedure must be reported to
tion of random and severe flaws. In addition, attention should
allow replication.
be given to pre-test storage of test specimens in controlled
8.2.2 As-Fabricated—The tensile test specimen should
environments or desiccators to avoid unquantifiable environ-
simulatethesurface/edgeconditionsandprocessingrouteofan
mental degradation of specimens prior to testing.)
application where no machining is used; for example, as-cast,
sintered, or injection-molded part. No additional machining
8.3 Number of Test Specimens—A minimum of five test
specifications are relevant.As-processed test specimens might
specimens tested validly is required for the purposes of
possess rough surface textures and nonparallel edges, and as
estimating a mean. A greater number of test specimens tested
such may cause excessive misalignment or be prone to
validlymaybenecessaryifestimatesregardingtheformofthe
non-gage section fractures, or both.
strength distribution are required. If material cost or test
8.2.3 Application-Matched Machining—The tensile test
specimenavailabilitylimitsthenumberofpossibletests,fewer
specimen should have the same surface/edge preparation as
tests can be conducted to determine an indication of material
that given to the component. Unless the process is proprietary,
properties.
the report should be specific about the stages of material
8.4 Valid Test—A valid individual test is one that meets all
removal, wheel grits, wheel bonding, amount of material
the following requirements—all the testing requirements of
removed per pass, and type of coolant used.
this test method, and final fracture occurs in the uniformly
8.2.4 Customary Practices—In instances where customary
stressed gage section unless those tests fracturing outside the
machining procedure has been developed that is completely
gage section are interpreted as interrupted tests for the purpose
satisfactory for a class of materials (that is, it induces no
of censored test analyses.
unwanted surface/subsurface damage or residual stresses), this
procedure should be used.
9. Procedure
8.2.5 Standard Procedure—In instances where 8.2.2 – 8.2.4
are not appropriate, 8.2.5 should apply. Studies to evaluate the 9.1 Test Specimen Dimensions—Determine the thickness
machinability of CFCCs have not been completed. Therefore, and width of the gage section of each test specimen to within
thestandardprocedureof8.2.5canbeviewedasstarting-point 0.02 mm. Make measurements on at least three different
guidelines and a more stringent procedure may be necessary. cross-sectional planes in the gage section. To avoid damage in
C1275 − 18
the critical gage section area, it is recommended that these strain dependent. Generally, displacement or strain-controlled
measurementsbemadeeitheroptically(forexample,anoptical tests are employed in such cumulative damage or yielding
comparator) or mechanically using a self-limiting (friction or deformation processes to prevent a “runaway” condition (that
ratchet mechanism), flat, anvil-type micrometer. When mea- is, rapid uncontrolled deformation and fracture) characteristic
suring dimensions between the woven faces of woven
of force- or stress-controlled tests. Thus, to elucidate the
materials, use a self-limiting (friction or ratchet mechanism), potential “toughening” mechanisms under controlled fracture
flat,anvil-typemicrometerhavinganvilcross-sectionaldimen-
of the CFCC, displacement or strain cont
...