ASTM C1359-18e1

Standard Test Method for Monotonic Tensile Strength Testing of Continuous Fiber-Reinforced Advanced Ceramics With Solid Rectangular Cross Section Test Specimens at Elevated Temperatures

SIGNIFICANCE AND USE
4.1 This test method may be used for material development, material comparison, quality assurance, characterization, reliability assessment, and design data generation.  
4.2 Continuous fiber-reinforced ceramic matrix composites generally characterized by crystalline matrices and ceramic fiber reinforcements are candidate materials for structural applications requiring high degrees of wear and corrosion resistance, and elevated-temperature inherent damage tolerance (that is, toughness). In addition, continuous fiber-reinforced glass (amorphous) matrix composites are candidate materials for similar but possibly less demanding applications. Although flexural test methods are commonly used to evaluate strengths of monolithic advanced ceramics, the nonuniform stress distribution of the flexure test specimen, in addition to dissimilar mechanical behavior in tension and compression for CFCCs, leads to ambiguity of interpretation of strength results obtained from flexure tests for CFCCs. Uniaxially loaded tensile strength tests provide information on mechanical behavior and strength for a uniformly stressed material.  
4.3 Unlike monolithic advanced ceramics that fracture catastrophically from a single dominant flaw, CFCCs generally experience “graceful” (that is, non-catastrophic, ductile-like stress-strain behavior) fracture from a cumulative damage process. Therefore, the volume of material subjected to a uniform tensile stress for a single uniaxially loaded tensile test may not be as significant a factor in determining the ultimate strengths of CFCCs. However, the need to test a statistically significant number of tensile test specimens is not obviated. Therefore, because of the probabilistic nature of the strengths of the brittle fibers and matrices of CFCCs, a sufficient number of test specimens at each testing condition is required for statistical analysis and design. Studies to determine the influence of test specimen volume or surface area on strength distributi...
SCOPE
1.1 This test method covers the determination of tensile strength, including stress-strain behavior, under monotonic uniaxial loading of continuous fiber-reinforced advanced ceramics at elevated temperatures. This test method addresses, but is not restricted to, various suggested test specimen geometries as listed in the appendixes. In addition, test specimen fabrication methods, testing modes (force, displacement, or strain control), testing rates (force rate, stress rate, displacement rate, or strain rate), allowable bending, temperature control, temperature gradients, and data collection and reporting procedures are addressed. 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 applies primarily to advanced ceramic matrix composites with continuous fiber reinforcement: unidirectional (1D), bidirectional (2D), and tridirectional (3D) or other multi-directional reinforcements. In addition, this test method may also be used with glass (amorphous) matrix composites with 1D, 2D, 3D, and other multi-directional continuous fiber reinforcements. This test method does not directly address discontinuous fiber-reinforced, whisker-reinforced, or particulate-reinforced ceramics, although the test methods detailed here may be equally applicable to these composites.  
1.3 The values stated in SI units are to be regarded as the standard and are in accordance with IEEE/ASTM SI 10.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Refer to Section 7 for specific precautions.  
1.5 ...

General Information

• Status: Published
• Publication Date: 31-Jul-2018
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: C28 - Advanced Ceramics
• Drafting Committee: C28.07 - Ceramic Matrix Composites

Relations

• Replaces: ASTM C1359-18 - Standard Test Method for Monotonic Tensile Strength Testing of Continuous Fiber-Reinforced Advanced Ceramics with Solid Rectangular Cross Section Test Specimens at Elevated Temperatures
• Effective Date: 01-Aug-2018
• Refers: ASTM D6856/D6856M-23 - Standard Guide for Testing Fabric-Reinforced “Textile” Composite Materials
• Effective Date: 01-Nov-2023
• Refers: ASTM D3878-19a - Standard Terminology for Composite Materials
• Effective Date: 15-Oct-2019
• Refers: ASTM C1145-19 - Standard Terminology of Advanced Ceramics
• Effective Date: 01-Jul-2019
• Refers: ASTM D3878-19 - Standard Terminology for Composite Materials
• Effective Date: 15-Apr-2019
• Refers: ASTM D3878-18 - Standard Terminology for Composite Materials
• Effective Date: 01-Apr-2018
• Refers: ASTM D6856/D6856M-03(2016) - Standard Guide for Testing Fabric-Reinforced “Textile” Composite Materials
• Effective Date: 01-Sep-2016
• Refers: ASTM D3878-16 - Standard Terminology for Composite Materials
• Effective Date: 01-Aug-2016
• Refers: ASTM D3878-15 - Standard Terminology for Composite Materials
• Effective Date: 01-Jul-2015
• Refers: ASTM E4-14 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2014
• Refers: ASTM E220-13 - Standard Test Method for Calibration of Thermocouples By Comparison Techniques
• Effective Date: 01-Nov-2013
• Refers: ASTM D3878-07(2013) - Standard Terminology for Composite Materials
• Effective Date: 01-May-2013
• Refers: ASTM C1145-06(2013) - Standard Terminology of Advanced Ceramics
• Effective Date: 01-Feb-2013
• Refers: ASTM C1145-06(2013)e1 - Standard Terminology of Advanced Ceramics
• Effective Date: 01-Feb-2013
• Refers: ASTM E1012-12e1 - Standard Practice for Verification of Testing Frame and Specimen Alignment Under Tensile and Compressive Axial Force Application
• Effective Date: 01-Jun-2012

Overview

ASTM C1359-18e1 is the recognized standard test method developed by ASTM International for evaluating the monotonic tensile strength of continuous fiber-reinforced advanced ceramics with solid rectangular cross-section specimens at elevated temperatures. This test method is essential for understanding the mechanical performance of advanced ceramic matrix composites (CMCs), especially when they are reinforced with continuous fibers and subjected to high-temperature environments.

The standard addresses not only specimen geometries but also covers specimen fabrication, loading modes (force, displacement, or strain control), testing rates, allowable bending, temperature control, and detailed data collection and reporting procedures. The results provide key mechanical property data, including stress-strain behavior, needed for material development, characterization, quality assurance, and design in demanding engineering applications.

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Key Topics

• Tensile Testing at Elevated Temperatures: This method determines the monotonic tensile strength and complete stress-strain behavior for advanced CMCs under continuous, uniaxial loading with no reversals, which closely simulates real-world loading scenarios in service environments.
• Material Coverage: Primarily focuses on advanced ceramics reinforced with continuous fibers (unidirectional/1D, bidirectional/2D, tridirectional/3D, or multidirectional). It is also applicable to glass matrix composites with similar fiber architectures.
• Significance of Test Results: The information is valuable for:
  • Material comparison and selection
  • Quality assurance processes
  • Characterization and reliability assessment
  • Generation of meaningful design data
• Composites Behavior: Unlike monolithic ceramics that exhibit brittle, catastrophic failure from a single flaw, continuous fiber-reinforced ceramics generally demonstrate gradual, damage-tolerant (ductile-like) fracture behavior, making tensile testing particularly informative.
• Specimen Preparation and Testing: Addresses the effects of test environment, specimen surface preparation, gripping mechanisms, strain measurement accuracy, and specimen alignment to ensure valid, reproducible results.
• Statistical Considerations: Due to inherent variability in brittle fibers and ceramic matrices, testing multiple specimens under each condition is necessary for statistical analysis and robust design inputs.

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Applications

The ASTM C1359-18e1 standard is instrumental in industries and research areas that utilize advanced ceramics and ceramic matrix composites, especially when high wear, corrosion resistance, and performance at elevated temperatures are required. Typical application areas include:

• Aerospace: Thermal protection systems, rocket engines, and structural components exposed to high stresses and temperatures.
• Energy: Components in turbines, boilers, and high-temperature reactors, requiring longevity and structural integrity.
• Automotive: Engine parts, brakes, and exhaust systems where advanced ceramics may replace metals for weight or performance benefits.
• Electronics: Substrates or insulators operating under high-temperature or harsh environmental conditions.
• Industrial Processing: Kiln furniture, cutting tools, and other equipment subjected to aggressive wear and heat.

This test method is valued in R&D for new material development, benchmarking different composite architectures, and qualifying materials for critical service.

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Related Standards

For comprehensive material evaluation and testing practices in ceramics and composite materials, consider these referenced and related ASTM standards:

• ASTM C1145: Terminology of Advanced Ceramics
• ASTM D3379: Test Method for Tensile Strength and Young’s Modulus for High-Modulus Single-Filament Materials
• ASTM D3878: Terminology for Composite Materials
• ASTM D6856: Guide for Testing Fabric-Reinforced “Textile” Composite Materials
• ASTM E4: Practices for Force Verification of Testing Machines
• ASTM E6: Terminology Relating to Mechanical Testing Methods
• ASTM E21: Test Methods for Elevated Temperature Tension Tests of Metallic Materials
• ASTM E83: Practice for Verification and Classification of Extensometer Systems
• ASTM E220: Test Method for Calibration of Thermocouples by Comparison Techniques
• ASTM E1012: Practice for Verification of Testing Frame and Specimen Alignment

Each of these standards complements ASTM C1359-18e1 by providing guidelines for terminology, equipment calibration, and additional property measurements, ensuring best practices for ceramics mechanical testing.

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Keywords: ASTM C1359-18e1, monotonic tensile strength, ceramic matrix composites, advanced ceramics testing, high-temperature mechanical properties, continuous fiber reinforcement, tensile testing standard, ceramic materials, composite material characterization, elevated temperature test methods.

Standards Content (Sample)

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.
´1
Designation: C1359 − 18
Standard Test Method for
Monotonic Tensile Strength Testing of Continuous Fiber-
Reinforced Advanced Ceramics With Solid Rectangular
Cross Section Test Specimens at Elevated Temperatures
This standard is issued under the fixed designation C1359; 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.
ε NOTE—Fig. 12 was updated editorially in September 2018.
1. Scope* priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 This test method covers the determination of tensile
Refer to Section 7 for specific precautions.
strength, including stress-strain behavior, under monotonic
1.5 This international standard was developed in accor-
uniaxial loading of continuous fiber-reinforced advanced ce-
dance with internationally recognized principles on standard-
ramics at elevated temperatures. This test method addresses,
ization established in the Decision on Principles for the
but is not restricted to, various suggested test specimen
Development of International Standards, Guides and Recom-
geometries as listed in the appendixes. In addition, test
mendations issued by the World Trade Organization Technical
specimen fabrication methods, testing modes (force,
Barriers to Trade (TBT) Committee.
displacement, or strain control), testing rates (force rate, stress
rate, displacement rate, or strain rate), allowable bending,
2. Referenced Documents
temperature control, temperature gradients, and data collection
and reporting procedures are addressed. Tensile strength as 2.1 ASTM Standards:
C1145Terminology of Advanced Ceramics
used in this test method refers to the tensile strength obtained
undermonotonicuniaxialloading,wheremonotonicreferstoa D3379TestMethodforTensileStrengthandYoung’sModu-
lus for High-Modulus Single-Filament Materials
continuous nonstop test rate with no reversals from test
initiation to final fracture. D3878Terminology for Composite Materials
D6856/D6856MGuide for Testing Fabric-Reinforced “Tex-
1.2 This test method applies primarily to advanced ceramic
tile” Composite Materials
matrix composites with continuous fiber reinforcement: unidi-
E4Practices for Force Verification of Testing Machines
rectional (1D), bidirectional (2D), and tridirectional (3D) or
E6Terminology Relating to Methods of MechanicalTesting
other multi-directional reinforcements. In addition, this test
E21TestMethodsforElevatedTemperatureTensionTestsof
method may also be used with glass (amorphous) matrix
Metallic Materials
composites with 1D, 2D, 3D, and other multi-directional
E83Practice for Verification and Classification of Exten-
continuous fiber reinforcements. This test method does not
someter Systems
directly address discontinuous fiber-reinforced, whisker-
E220Test Method for Calibration of Thermocouples By
reinforced,orparticulate-reinforcedceramics,althoughthetest
Comparison Techniques
methods detailed here may be equally applicable to these
E337Test Method for Measuring Humidity with a Psy-
composites.
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
1.3 The values stated in SI units are to be regarded as the
peratures)
standard and are in accordance with IEEE/ASTM SI 10.
E1012Practice for Verification of Testing Frame and Speci-
1.4 This standard does not purport to address all of the men Alignment Under Tensile and Compressive Axial
safety concerns, if any, associated with its use. It is the Force Application
responsibility of the user of this standard to establish appro- IEEE/ASTM SI 10American National Standard for Metric
Practice
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 Aug. 1, 2018. Published September 2018. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1996. Last previous edition approved in 2013 as C1359–13. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C1359-18E01. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
C1359 − 18
3. Terminology first stress at which a permanent offset strain is detected in the
unloading stress-strain (elastic limit) curve.
3.1 Definitions:
–2
3.2.10 modulus of elasticity [FL ], n—ratio of stress to
3.1.1 Definitions of terms relating to tensile testing, ad-
corresponding strain below the proportional limit. E6
vanced ceramics, and fiber-reinforced composites as they
–3
appear inTerminology E6,Terminology C1145, andTerminol-
3.2.11 modulus of resilience [FLL ], n—strain energy per
ogy D3878, respectively, apply to the terms used in this test
unitvolumerequiredtoelasticallystressthematerialfromzero
method. Pertinent definitions are shown in the following with
totheproportionallimit,indicatingtheabilityofthematerialto
theappropriatesourcegiveninboldtext.Additionaltermsused
absorb energy when deformed elastically and return it when
in conjunction with this test method are defined in 3.2.
unloaded. C1145
3.2 Definitions of Terms Specific to This Standard: –3
3.2.12 modulus of toughness [FLL ], n—strain energy per
3.2.1 advanced ceramic, n—highly engineered, high-
unit volume required to stress the material from zero to final
performance, predominately nonmetallic, inorganic, ceramic
fracture, indicating the ability of the material to absorb energy
material having specific functional attributes. C1145
beyond the elastic range (that is, damage tolerance of the
–1
3.2.2 axial strain [LL ], n—average longitudinal strains material). C1145
measured at the surface on opposite sides of the longitudinal 3.2.12.1 Discussion—Themodulusoftoughnesscanalsobe
axisofsymmetryofthespecimenbytwostrainsensingdevices referred to as the cumulative damage energy and as such is
located at the mid length of the reduced section. E1012 regardedasanindicationoftheabilityofthematerialtosustain
–1
damage rather than as a material property. Fracture mechanics
3.2.3 bending strain [LL ], n—difference between the
methods for the characterization of CFCCs have not been
strainatthesurfaceandtheaxialstrain.Ingeneral,thebending
developed. The determination of the modulus of toughness as
strain varies from point to point around and along the reduced
provided in this test method for the characterization of the
section of the specimen. E1012
cumulative damage process in CFCCs may become obsolete
3.2.4 breaking force [F], n—force at which fracture occurs.
when fracture mechanics methods for CFCCs become avail-
E6
able.
3.2.5 ceramic matrix composite, n—material consisting of
–2
3.2.13 proportional limit stress [FL ], n—greatest stress
two or more materials (insoluble in one another), in which the
whichamaterialiscapableofsustainingwithoutanydeviation
major,continuouscomponent(matrixcomponent)isaceramic,
from proportionality of stress to strain (Hooke’s law). E6
while the secondary component(s) (reinforcing component)
3.2.13.1 Discussion—Many experiments have shown that
may be ceramic, glass-ceramic, glass, metal, or organic in
valuesobservedfortheproportionallimitvarygreatlywiththe
nature. These components are combined on a macroscale to
sensitivity and accuracy of the testing equipment, eccentricity
form a useful engineering material possessing certain proper-
of loading, the scale to which the stress-strain diagram is
ties or behavior not possessed by the individual constituents.
plotted, and other factors. When determination of proportional
C1145
limit is required, the procedure and sensitivity of the test
3.2.6 continuous fiber-reinforced ceramic matrix composite
equipment shall be specified.
(CFCC), n—ceramic matrix composite in which the reinforc-
3.2.14 percentbending,n—bendingstraintimes100divided
ing phase consists of a continuous fiber, continuous yarn, or a
by the axial strain. E1012
woven fabric. C1145
3.2.15 slow crack growth (SCG), n—subcritical crack
–2
3.2.7 fracture strength [FL ], n—tensile stress that the
growth(extension)whichmayresultfrom,butisnotrestricted
material sustains at the instant of fracture. Fracture strength is
to, such mechanisms as environmentally assisted stress corro-
calculated from the force at fracture during a tension test
sion or diffusive crack growth. C1145
carried to rupture and the original cross-sectional area of the
–2
3.2.16 tensile strength [FL ], n—maximum tensile stress
specimen. E6
which a material is capable of sustaining. Tensile strength is
3.2.7.1 Discussion—In some cases, the fracture strength
calculated from the maximum force during a tension test
may be identical to the tensile strength if the force at fracture
carried to rupture and the original cross-sectional area of the
is the maximum for the test.
specimen. E6
3.2.8 gage length [L], n—original length of that portion of
4. Significance and Use
the specimen over which strain or change of length is
determined. E6 4.1 Thistestmethodmaybeusedformaterialdevelopment,
–2
material comparison, quality assurance, characterization, reli-
3.2.9 matrix-cracking stress [FL ], n—applied tensile
ability assessment, and design data generation.
stress at which the matrix cracks into a series of roughly
parallel blocks normal to the tensile stress. C1145 4.2 Continuous fiber-reinforced ceramic matrix composites
3.2.9.1 Discussion—In some cases, the matrix-cracking generally characterized by crystalline matrices and ceramic
stress may be indicated on the stress-strain curve by deviation fiber reinforcements are candidate materials for structural
from linearity (proportional limit) or incremental drops in the applications requiring high degrees of wear and corrosion
stress with increasing strain. In other cases, especially with resistance, and elevated-temperature inherent damage toler-
materials which do not possess a linear portion of the stress- ance (that is, toughness). In addition, continuous fiber-
straincurve,thematrix-crackingstressmaybeindicatedasthe reinforced glass (amorphous) matrix composites are candidate
´1
C1359 − 18
materials for similar but possibly less demanding applications. 5. Interferences
Although flexural test methods are commonly used to evaluate
5.1 Test environment (vacuum, inert gas, ambient air, etc.),
strengths of monolithic advanced ceramics, the nonuniform
including moisture content (for example, relative humidity),
stress distribution of the flexure test specimen, in addition to
may have an influence on the measured tensile strength. In
dissimilar mechanical behavior in tension and compression for
particular, the behavior of materials susceptible to slow crack
CFCCs, leads to ambiguity of interpretation of strength results
growth fracture will be strongly influenced by test
obtained from flexure tests for CFCCs. Uniaxially loaded
environment, testing rate, and elevated temperature of the test.
tensile strength tests provide information on mechanical be-
Conduct tests to evaluate the maximum strength potential of a
havior and strength for a uniformly stressed material.
material in inert environments or at sufficiently rapid testing
rates, or both, to minimize slow crack growth effects.
4.3 Unlikemonolithicadvancedceramicsthatfracturecata-
Conversely, conduct tests in environments or at test modes, or
strophically from a single dominant flaw, CFCCs generally
both, and rates representative of service conditions to evaluate
experience “graceful” (that is, non-catastrophic, ductile-like
materialperformanceunderuseconditions.Monitorandreport
stress-strain behavior) fracture from a cumulative damage
relative humidity (RH) and temperature when testing is con-
process. Therefore, the volume of material subjected to a
ductedinuncontrolledambientairwiththeintentofevaluating
uniform tensile stress for a single uniaxially loaded tensile test
maximum strength potential.Testing at humidity levels >65%
may not be as significant a factor in determining the ultimate
RH is not recommended.
strengths of CFCCs. However, the need to test a statistically
significant number of tensile test specimens is not obviated.
5.2 Surface preparation of test specimens, although nor-
Therefore, because of the probabilistic nature of the strengths
mallynotconsideredamajorconcerninCFCCs,canintroduce
ofthebrittlefibersandmatricesofCFCCs,asufficientnumber
fabricationflawswhichmayhavepronouncedeffectsontensile
of test specimens at each testing condition is required for
mechanical properties and behavior (for example, shape and
statistical analysis and design. Studies to determine the influ-
level of the resulting stress-strain curve, tensile strength and
ence of test specimen volume or surface area on strength
strain, proportional limit stress and strain, and so forth).
distributions for CFCCs have not been completed. It should be
Machining damage introduced during test specimen prepara-
noted that tensile strengths obtained using different recom-
tion can be either a random interfering factor in the determi-
mended tensile test specimen geometries with different vol-
nationofultimatestrengthofpristinematerial(thatis,increase
umes of material in the gage sections may be different due to
frequency of surface-initiated fractures compared to volume-
these volume differences.
initiated fractures), or an inherent part of the strength charac-
teristics to be measured. Surface preparation can also lead to
4.4 Tensile tests provide information on the strength and
the introduction of residual stresses. Universal or standardized
deformation of materials under uniaxial tensile stresses. Uni-
methods for surface preparation do not exist. In addition, the
form stress states are required to effectively evaluate any
nature of fabrication used for certain composites (for example,
nonlinear stress-strain behavior that may develop as the result
chemical vapor infiltration or hot pressing) may require the
ofcumulativedamageprocesses(forexample,matrixcracking,
testing of test specimens in the as-processed condition (that is,
matrix/fiber debonding, fiber fracture, delamination, and so
it may not be possible to machine the test specimen faces
forth) that may be influenced by testing mode, testing rate,
without compromising the in-plane fiber architecture). Final
effects of processing or combinations of constituent materials,
machining steps may or may not negate machining damage
environmental influences, or elevated temperatures. Some of
introduced during the initial machining. Therefore, report test
these effects may be consequences of stress corrosion or
specimen fabrication history since it may play an important
subcritical (slow) crack growth that can be minimized by
role in the measured strength distributions.
testingatsufficientlyrapidratesasoutlinedinthistestmethod.
5.3 Bending in uniaxial tensile tests can cause or promote
4.5 The results of tensile tests of test specimens fabricated
nonuniform stress distributions with maximum stresses occur-
to standardized dimensions from a particular material or
ring at the test specimen surface, leading to nonrepresentative
selected portions of a part, or both, may not totally represent
fracturesoriginatingatsurfacesorneargeometricaltransitions.
the strength and deformation properties of the entire, full-size
Bending may be introduced from several sources, including
endproductoritsin-servicebehaviorindifferentenvironments
misaligned load trains, eccentric or misshaped test specimens,
or various elevated temperatures.
and nonuniformly heated test specimens or grips. In addition,
4.6 For quality control purposes, results derived from stan- if deformations or strains are measured at surfaces where
dardizedtensiletestspecimensmaybeconsideredindicativeof
maximum or minimum stresses occur, bending may introduce
theresponseofthematerialfromwhichtheyweretakenforthe over or under measurement of strains depending on the
particular primary processing conditions and post-processing
location of the strain measuring device on the test specimen.
heat treatments. Similarly, fracture from surface flaws may be accentuated or
suppressed by the presence of the nonuniform stresses caused
4.7 The tensile behavior and strength of a CFCC are
by bending.
dependentonitsinherentresistancetofracture,thepresenceof
flaws, or damage accumulation processes, or both.Analysis of 5.4 Fractures that initiate outside the uniformly stressed
fracturesurfacesandfractography,thoughbeyondthescopeof gage section of a test specimen may be due to factors such as
this test method, is recommended. stress concentrations or geometrical transitions, extraneous
´1
C1359 − 18
FIG. 1 Schematic Diagram of One Possible Apparatus for Conducting a Uniaxially Loaded Tensile Test
forces used in determining tensile strength shall be accurate to
within 61%atanyforcewithintheselectedforcerangeofthe
testing machine.Aschematic 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 force applied by the testing
machinetothetestspecimen.Thebrittlenatureofthematrices
of CFCCs requires a uniform interface between the grip
components and the gripped section of the test specimen. Line
or point contacts and nonuniform pressure can produce
Hertzian-type stresses, leading to crack initiation and fracture
of the test specimen in the gripped section. Gripping devices
canbeclassifiedgenerallyasthoseemployingactiveandthose
employingpassivegripinterfacesasdiscussedinthefollowing
NOTE 1—Shape is that of a quarter section of a face-loaded tensile test
paragraphs. Uncooled grips located inside the heated zone are
specimen.
termed “hot grips,” and generally produce almost no thermal
FIG. 2 Temperature Distributions in a Reduced Gage Section Test gradient in the test specimen but at the relative expense of grip
Specimen for Various Types of Gripping Arrangements
materials of at least the same temperature capability as the test
materialandincreaseddegradationofthegripsduetoexposure
stressesintroducedbygripping,orstrength-limitingfeaturesin
to the elevated-temperature oxidizing environment. Grips lo-
the microstructure of the test specimen. Such non-gage section cated outside the heated zone surrounding the test specimen
fractures will normally constitute invalid tests. In addition, for
may or may not employ cooling. Uncooled grips located
face-loaded geometries, gripping pressure is a key variable in outsidetheheatedzonearetermed“warmgrips,”andgenerally
the initiation of fracture. Insufficient pressure can shear the
induce a mild thermal gradient in the test specimen but at the
outer plies in laminated CFCCs, while too much pressure can relativeexpenseofelevated-temperaturealloysinthegripsand
cause local crushing of the CFCC and initiate fracture in the
increased degradation of the grips due to exposure to the
vicinity of the grips. elevated-temperature oxidizing environment. Cooled grips lo-
cated outside the heated zone are termed “cold grips,” and
6. Apparatus
generally induce a steep thermal gradient in the test specimen
6.1 Testing Machines—Machines used for tensile testing (as shown by example in Fig. 2) at a greater relative expense
shall conform to Practices E4. As defined in Practices E4, because of grip cooling equipment and allowances, although
´1
C1359 − 18
the test specimen/grip interface. Tolerances will vary depend-
ing on the exact configuration as shown in the appropriate test
specimen drawings.
6.2.1.3 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. Keep the serra-
tions clean and well defined but not overly sharp. The length
and width of the grip faces shall be equal to or greater than the
respective length and width of the gripped sections of the test
FIG. 3 Example of a Direct Lateral Pressure Grip Face for a Face-
specimen.
Loaded Grip Interface
6.2.1.4 Passive Grip Interfaces—Passive grip interfaces
transmit the force applied by the test machine to the test
specimen through a direct mechanical link. These mechanical
links transmit the test forces to the test specimen via geometri-
with the advantage of consistent alignment and little degrada-
cal features of the test specimens such as shank shoulders or
tion from exposure to elevated temperatures.
holesinthegrippedhead.Thus,theimportantaspectofpassive
NOTE 1—The expense of the cooling system for cold grips is balanced
grip interfaces is uniform contact between the gripped section
against maintaining alignment that remains consistent from test to test
of the test specimen and the grip faces.
(stable grip temperature) and decreased degradation of the grips due to
6.2.1.5 For flat test specimens, passive grips may act either
exposure to the elevated-temperature oxidizing environment. When grip
through edge loading via grip interfaces at the shoulders of the
cooling is employed, means should be provided to control the cooling
medium to maximum fluctuations of 5 K (less than 1 K preferred) about
testspecimenshank (4)orbycombinationsoffaceloadingand
a setpoint temperature (1) over the course of the test to minimize
pin loading via pins at holes in the gripped test specimen head
thermally induced strain changes in the test specimen. In addition,
(5, 6). Close tolerances of linear and angular dimensions of
opposing grip temperatures should be maintained at uniform and consis-
shoulder and grip interfaces are required to promote uniform
tent temperatures within 65 K (less than 61 K preferred) (1) so as to
avoid introducing unequal thermal gradients and subsequent nonuniaxial contact along the entire test specimen/grip interface, as well as
stresses in the test specimen. Generally, the need for control of grip
to provide for non-eccentric loading as shown in Fig. 5.In
temperature fluctuations or differences may be indicated if test specimen
addition, moderately close tolerances are required for center-
gage-sectiontemperaturescannotbemaintainedwithinthelimitsrequired
linecoincidenceanddiametersofthepinsandholeasindicated
in 9.3.2.
in Fig. 6.
6.2.1.1 Active Grip Interfaces—Active grip interfaces re-
6.2.1.6 When using edge-loaded test specimens, lateral
quire a continuous application of a mechanical, hydraulic, or
centering of the test specimen within the grip attachments is
pneumatic force to transmit the force applied by the test
accomplished by use of wedge-type inserts machined to fit
machine to the test specimen. Generally, these types of grip
within the grip cavity. In addition, wear of the grip cavity can
interfaces cause a force to be applied normal to the surface of
bereducedbyuseofthethinbrasssheetsbetweenthegripand
the gripped section of the test specimen. Transmission of the
test specimen without adversely affecting test specimen align-
uniaxialforceappliedbythetestmachineisthenaccomplished
ment.
by friction between the test specimen and the grip faces.Thus,
6.2.1.7 Thepinsintheface/pin-loadedgripareprimarilyfor
important aspects of active grip interfaces are uniform contact
alignment purposes and force transmission. Secondary force
between the gripped section of the test specimen and the grip
transmissionisthroughfaceloadingviamechanicallyactuated
facesandconstantcoefficientoffrictionoverthetestspecimen/
wedge grip faces. Proper tightening of the wedge grip faces
grip interface. In addition, note that fixed-displacement active
against the test specimen to prevent slipping while avoiding
grips set at ambient temperatures may introduce excessive
compressivefractureofthetestspecimengrippedsectionmust
gripping stresses due to thermal expansion of the test material
be determined for each material and test specimen type.
when the test specimen is heated to the test temperature.
6.2.1.8 Passive grips employing single pins in each gripped
Provide means to avoid such excessive stresses.
section of the test specimen as the primary force transfer
6.2.1.2 For flat test specimens, face-loaded grips, either by
mechanism are not recommended. Relatively low interfacial
direct lateral pressure grip faces (2) or by indirect wedge-type
shear strengths compared to longitudinal tensile strengths in
grip faces, act as the grip interface (3) as illustrated in Fig. 3
CFCCs (particularly for 1D reinforced materials loaded along
and Fig. 4, respectively. Close tolerances are required for the
the fiber direction) may promote non-gage section fractions
flatness and parallelism, as well as for the wedge angle of the
along interfaces, particularly at geometric transitions or at
wedge grip faces. In addition, the thickness, flatness, and
discontinuities such as holes.
parallelism of the gripped section of the test specimen must be
6.3 Force Train Couplers:
withinsimilarlyclosetolerancestopromoteuniformcontactat
6.3.1 General—Various types of devices (load train cou-
plers)maybeusedtoattachtheactiveorpassivegripinterface
assemblies to the testing machine. The load train couplers, in
The boldface numbers given in parentheses refer to a list of references at the
end of the text. conjunction with the type of gripping device, play major roles
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FIG. 4 Example of Indirect Wedge-Type Grip Faces for a Face-Loaded Grip Interface
FIG. 5 Example of a Edge-Loaded, Passive Grip Interface (4)
FIG. 6 Example of Pin/Face-Loaded, Passive Grip Interface (5)
in the alignment of the load train and thus subsequent bending aligning non-fixed couplers does not automatically guarantee
imposed in the test specimen. Load train couplers can be low bending in the gage section of the tensile test specimen.
classified generally as fixed and non-fixed as discussed in the Well-aligned fixed or self-aligning non-fixed couplers provide
following paragraphs. Use of well-aligned fixed or self- for well-aligned load trains, but the type and operation of grip
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C1359 − 18
interfaces,aswellastheas-fabricateddimensionsofthetensile 6.3.3.1 Non-fixedloadtraincouplersareusefulintestingof
test specimen, can add significantly to the final bending CFCCs at rapid test rates or in load control where the
imposed in the gage section of the test specimen.
cumulativedamagefractureprocessmaynotbeasmacroscopi-
6.3.1.1 Regardless of which type of coupler is used, verify cally apparent. If the material exhibits such fracture behavior,
alignment of the testing system at a minimum at the beginning
the self-aligning feature of the non-fixed coupler allows
and end of a test series, unless the conditions for verifying rotation of the gripped section of the test specimen, thus
alignment are otherwise met. An additional verification of
promotinganonuniformstressintheremainingligamentofthe
alignment is recommended, although not required, at the
gage section.
middle of the test series. Use either a dummy or actual test
6.4 Strain Measurement—Determine strain at elevated tem-
specimen. Allowable bending requirements are discussed in
peratures by means of a suitable extensometer.
6.5. See Practice E1012 for discussions of alignment and
6.4.1 Extensometers used for tensile testing of CFCC test
Appendix X1 for suggested procedures specific to this test
specimens shall satisfy Practice E83, Class B-1 requirements.
method.Atest series is interpreted to mean a discrete group of
tests on individual test specimens conducted within a discrete Calibrate extensometers periodically in accordance with Prac-
period of time on a particular material configuration, test tice E83. For extensometers which mechanically contact the
specimen geometry, test condition, or other uniquely definable test specimen, the contact shall not cause damage to the test
qualifier (for example, a test series composed of Material A specimen surface. However, shallow grooves (0.025 to
comprising ten test specimens of Geometry B tested at a fixed
0.051mm deep) machined into the surfaces of CFCCs to
rate in strain control to final fracture in ambient air).
prevent extensometer slippage have been shown to not have a
detrimental effect on failure strengths at elevated temperatures
NOTE 2—Tensile test specimens used for alignment verification should
(5). Choose extensometer contact probes which are chemically
be equipped with a recommended eight separate longitudinal strain gages
to determine bending contributions from both eccentric and angular compatible with the test material (for example, alumina exten-
misalignment of the grip heads. Ideally, the verification test specimen
someter extensions and SiC CFCC are incompatible). In
should be of identical material to that being tested. However, in the case
addition, support the weight of the extensometer so as not to
of CFCCs, the type of reinforcement or degree of residual porosity may
introduce bending greater than that allowed in 6.5. Finally,
complicate the consistent and accurate measurement of strain. Therefore,
an alternate material (isotropic, homogeneous, continuous) with similar configure the tips of the probes of contacting extensometers
elastic modulus, elastic strain capability, and hardness to the test material
(for example, sharp, knife edges, or chisel tips) so as to
may be used. In addition, dummy test specimens used for alignment
minimize slippage.
verification should have the same geometry and dimensions of the actual
test specimens, as well as similar mechanical properties as the test
6.5 Allowable Bending—Analytical and empirical studies
materialtoensuresimilaraxialandbendingstiffnesscharacteristicsasthe
(11) have concluded that for negligible effects on the estimates
actual test specimen and material.
of the strength distribution parameters (for example, Weibull
6.3.2 Fixed Load Train Couplers—Fixed couplers may
modulus, mˆ, and characteristic strength, σˆ ) of monolithic
θ
incorporate devices which require either a one-time, pre-test
advanced ceramics, allowable percent bending as defined in
alignmentadjustmentoftheloadtrainthatremainsconstantfor
Practice E1012 should not exceed five.These conclusions (11)
all subsequent tests or an in situ, pre-test alignment of the load
assume that tensile strength fractures are due to single fracture
train which is conducted separately for each test specimen and
origins in the volume of the material, all tensile test specimens
each test. Such devices (7, 8) usually employ angularity and
experienced the same level of bending, and that Weibull
concentricity adjusters to accommodate inherent load train
modulus, mˆ, was constant.
misalignments. Regardless of which method is used, verify
6.5.1 Similar studies of the effect of bending on the tensile
alignment verification as discussed in 6.3.1.1.
strength distributions of CFCCs do not exist. Until such
6.3.2.1 Fixed load train couplers are preferred in the mono-
informationisforthcomingforCFCCs,thistestmethodadopts
tonic testing of CFCCs because of the fracture behavior in
the recommendations for tensile testing of monolithic ad-
these materials. During the fracture process of CFCCs, the
vanced ceramics. Therefore, the recommended maximum al-
fixed coupler tends to hold the test specimen in an aligned
lowablepercentbendingattheonsetofthecumulativefracture
position and thus provides a continuous uniform stress across
process (for example, matrix-cracking stress) for test speci-
the remaining ligament of the gage section.
mens tested under this test method is five. Verify the testing
6.3.3 Non-Fixed Load Train Couplers—Non-fixed couplers
system such that percent bending does not exceed five at a
may incorporate devices which promote self-alignment of the
meanstrainequaltoeitherone-halftheanticipatedstrainatthe
load train during the movement of the crosshead or actuator.
onset of the cumulative fracture process (for example, matrix-
Such devices rely upon freely moving linkages to eliminate
cracking stress) or a strain of 0.0005 (that is, 500 microstrain),
applied moments as the load train components are loaded.
whichever is greater. Unless all test specimens are properly
Knife edges, universal joints, hydraulic couplers, or air bear-
strain gaged and percent bending monitored until the onset of
ings are examples (5, 9, 10) of such devices. Examples of two
the cumulative fracture process, there will be no record of
suchdevicesareshowninFig.7.Althoughnon-fixedloadtrain
percent bending at the onset of fracture for each test specimen.
couplersaredesignedtobeself-aligningandthuseliminatethe
Therefore, verify the alignment of the testing system. See
need to evaluate the bending in the test specimen for each test,
Practice E1012 for discussions of alignment and Appendix X1
this alignment must be confirmed. Verify the operation of the
couplers as discussed in 6.3.1.1. for suggested procedures specific to this test method.
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C1359 − 18
FIG. 7 Examples of Hydraulic, Self-Aligning, Non-Fixed Load Train Couplers (9, 10)
6.6 Heating Apparatus—The apparatus for, and method of, MNL12 (12).Firstly,thermocouplecalibrationandinstrument
heating the test specimens shall provide the temperature measuring errors initially produce uncertainty as to the exact
control necessary to satisfy the requirement of 9.3.2. temperature. Secondly, both thermocouples and measuring
6.6.1 Heating can be by indirect electrical resistance (heat- instruments may be subject to variations over time. Common
ing elements), direct induction, indirect induction through a errors encountered in the use of thermocouples to measure
susceptor,orradiantlampwiththetestspecimeninambientair temperatures include: calibration error, drift in calibration due
at atmospheric pressure, unless other environments are specifi- to contamination or deterioration with use, lead wire error,
cally applied and reported. error arising from method of attachment to the test specimen,
direct radiation of heat to the bead, heat conduction along
NOTE 3—Direct resistance heating is not recommended for heating
thermocouple wires, etc.
CFCCs due to possible differences of the electrical resistances of the
constituent materials that may produce nonuniform heating of the test
6.7.1.1 Measure temperature with thermocouples of known
specimen.
calibration (calibrated according to Test Method E220). Cali-
6.7 Temperature Measuring Apparatus—The method of braterepresentativethermocouplesfromeachlotofwiresused
temperature measurement shall be sufficiently sensitive and for making noble (for example, Pt or Rh/Pt) metal thermo-
reliable to ensure that the temperature of the test specimen is couples. Except for relatively low temperatures of exposure,
within the limits specified in 9.3.2. noble-metalthermocouplesareeventuallysubjecttoerrorupon
6.7.1 For test temperatures less than 2000 K, make primary reuse,unlessthedepthofimmersionandtemperaturegradients
temperature measurements with noble-metal thermocouples in of the initial exposure are reproduced. Consequently, calibrate
conjunction with potentiometers, millivoltmeters, or electronic noble-metal thermocouples using representative thermo-
temperature controllers or readout units, or all of these. Such couples. Do not reuse degraded noble-metal thermocouples
measurements are subject to two types of error as discussed in without proper treatment. This treatment includes clipping
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C1359 − 18
back the wire exposed to the hot zone, rewelding a thermo- be recorded but should not be used to define displacement or
couple bead, and properly annealing the rewelded thermo- strain in the gage section, especially when self-aligning cou-
couplebeadandwire.Anyreuseofnoble-metalthermocouples plers are used in the load train.
(except after relatively low-temperature use) without this 6.8.2 At a minimum, record temperature as single points at
precautionary treatment shall be accompanied by recalibration the initiation and completion of the actual test. However,
data demonstrating that calibration of the temperature reading temperature can also be recorded similarly to force and strain,
system was not unduly affected by the conditions of exposure. except the record can begin at the start of the heating of the
furnace (including ramp-up to test temperature) and ending at
6.7.1.2 Measurement of the drift in calibration of thermo-
the completion of the test.
couples during use is difficult. When drift is a problem during
tests, devise a method to check the readings of the thermo-
6.9 Dimension Measuring Devices—Micrometres and other
couples on the test specimen during the test. For reliable
devicesusedformeasuringlineardimensionsshallbeaccurate
calibration of thermocouples after use, reproduce the tempera-
and precise to at least one-half the smallest unit to which the
ture gradient of the test furnace during the recalibration.
individual dimension is required to be measured. For the
6.7.1.3 Thermocouples containing Pt are also subject to
purposes of this test method, cross-sectional dimensions shall
degradation in the presence of silicon and silicon-containing
be measured to within 0.02 mm, using dimension measuring
compounds. Platinum silicides may form leading to several
devices with accuracies of 0.01 mm.
possible outcomes. One outcome is the embrittlement of the
7. Precautionary Statements
noble-metal thermocouple tips and their eventual degradation
and breakage. Another outcome is the degradation of the
7.1 Duringtheconductofthistestmethod,thepossibilityof
silicon-containing material (for example, test specimen, fur-
flying fragments of broken test material may be great. The
nace heating elements, or refractory furnace materials). In all
brittle nature of advanced ceramics and the release of strain
cases, do not allow platinum-containing materials to contact
energy contribute to the potential release of uncontrolled
silicon-containing materials. In particular, do not allow noble-
fragments upon fracture. Means for containment and retention
metalthermocouplestocontactsilicon-basedtestmaterials(for
of these fragments for safety, as well as later fractographic
example, SiC or Si N ). In some cases (for example, when
3 4
reconstruction and analysis, is recommended.
using SiC heating elements), it is advisable to use ceramic-
7.2 Exposed fibers at the edges of CFCC test specimens
shielded noble-metal thermocouples to avoid the reaction of
present a hazard due to the sharpness and brittleness of the
the Pt-alloy thermocouples with the SiO gas generated by the
ceramic fiber. Inform all persons required to handle these
volatilization of the SiO protective layers of SiC heating
materials of such conditions and the proper handling tech-
elements.
niques.
6.7.1.4 Calibrate temperature measuring, controlling, and
recording instruments versus a secondary standard, such as
8. Test Specimen
precision potentiometer, optical pyrometer, or black-body thy-
8.1 Test Specimen Geometry:
ristor.Checkleadwireerrorwiththeleadwiresinplaceasthey
8.1.1 General—The geometry of tensile test specimens is
normally are used.
dependent on the ultimate use of the tensile strength data. For
6.7.2 For test temperatures greater than 2000 K, less-
example, if the tensile strength of an as-fabricated component
common temperature measurement devices such as thermo-
is required, the dimensions of the resulting tensile test speci-
couples of elevated-temperature, non noble-metal alloys (for
menmayreflectthethickness,width,andlengthrestrictionsof
example, W-Re) or optical pyrometry may be used. Since
the component. If it is desired to evaluate the effects of
widely recognized standards do not exist for these less-
interactions of various constituent materials for a particular
common devices, report the type of measurement device, its
CFCC manufactured via a particular processing route, then the
method of calibration, and its accuracy and precision.
size of the test specimen and resulting gage section will reflect
6.8 DataAcquisition—Ataminimum,obtainanautographic
the desired volume or surface area to be sampled. In addition,
record of applied load and gage section elongation or strain
grip interfaces and load train couplers as discussed in Section
versus time. Either analog chart recorders or digital data
6 will influence the final design of the test specimen geometry.
acquisition systems can be used for this purpose, although a
8.1.1.1 The following paragraphs discuss the more
digital record is recommended for ease of later data analysis.
common, and thus proven, of these test specimen geometries,
Ideally, use an analog chart recorder or plotter in conjunction
although any geometry is acceptable if it meets the gripping,
with the digital data acquisition system to provide an immedi-
fracture location, bending, and temperature profile require-
ate record of the test as a supplement to the digital record.
ments of this test method. Deviations from the recommended
Recording devices shall be accurate to within 61.0% of the
geometries may be necessary depending upon the particular
selected range for the testing system including readout unit, as
CFCC being evaluated. Conduct stress analyses of untried test
specified in Practices E4, and should have a minimum data
specimens to ensure that stress concentrations which can lead
acquisition rate of 10 Hz, with a response of 50 Hz deemed
to undesired fractures outside the gage sections do not exist.
more than sufficient.
Contoured test specimens by their nature contain inherent
6.8.1 Record strain or elongation, or both, of the gage stressconcentrationsduetogeometrictransitions.Stressanaly-
sectioneithersimilarlytotheforceorasindependentvariables ses can indicate the magnitude of such stress concentrations
of force. Crosshead displacement of the test machine may also while revealing the success of producing a uniform tensile
´1
C1359 − 18
stress state in the gage section of the test specimen. shank as shown in Figs. X2.1 and X2.2.Thus, the edge-loaded
Additionally, the success of an elevated-temperature tensile geometry may require somewhat intensive fabrication and
test will depend on the type of heating system, extent of test inspection procedures.
specimen heating, and test specimen geometry since these
8.1.3 Face-Loaded Flat Tensile Test Specimens—Figs.
factorsareallinterrelated.Forexample,thermalgradientsmay
X2.3-X2.5showexamplesofface-loadedtestspecimenswhich
introduce additional stress gradients in test specimens which
exploit the friction at the test specimen/grip interface to
may already exhibit stress gradients at ambient temperatures
transmit the uniaxial force applied by the test machine.
due to geometric transitions. Therefore, analyze untried test Important tolerances for the face-loaded geometry include
configurations simultaneously for both loading-induced stress
parallelism and flatness of faces, all of which will vary
gradients and thermally induced temperature gradients to depending on the exact configuration as shown in the appro-
ascertain any adverse interactions.
priate test specimen drawings.
8.1.1.2 Test specimens with contoured gage sections (tran- 8.1.3.1 For face-loaded test specimens, especially for
sition radii of >50 mm) are preferred to promote the tensile
straight-sided (that is, noncontoured) test specimens, end tabs
stresses with the greatest values in the uniformly stressed gage may be required to provide a compliant layer for gripping.
section (13) while minimizing the stress concentration due to
Balanced 0/90° cross-ply tabs made from unidirectional, non-
the geometrical transition of the radius. However, in certain woven E-glass have proven to be satisfactory for certain
instances(forexample,1DCFCCstestedalongthedirectionof
fiber-reinforcedpolymers.ForCFCCs,tabmaterialscomprised
the fibers), low interfacial shear strength rel
...