ASTM C1773-21

Standard Test Method for Monotonic Axial Tensile Behavior of Continuous Fiber-Reinforced Advanced Ceramic Tubular Test Specimens at Ambient Temperature

SIGNIFICANCE AND USE
5.1 This test method provides information on the uniaxial tensile properties and tensile stress-strain response of a ceramic composite tube—tensile strength and strain, fracture strength and strain, proportional limit stress and strain, tensile elastic modulus, etc. The information may be used for material development, material comparison, quality assurance, characterization, and design data generation.  
5.2 Continuous fiber-reinforced ceramic composites (CFCCs) are composed of continuous ceramic-fiber directional (1D, 2D, and 3D) reinforcements in a fine-grain-sized ((1, 2).3  
5.3 CFCC components have a distinctive and synergistic combination of material properties, interface coatings, porosity control, composite architecture (1D, 2D, and 3D), and geometric shape that are generally inseparable. Prediction of the mechanical performance of CFCC tubes (particularly with braid and 3D weave architectures) cannot be made by applying measured properties from flat CFCC plates to the design of tubes. Direct uniaxial tensile strength tests of CFCC tubes are needed to provide reliable information on the mechanical behavior and strength of tube geometries.  
5.4 CFCCs generally experience “graceful” fracture from a cumulative damage process, unlike monolithic advanced ceramics which fracture catastrophically from a single dominant flaw. The tensile behavior and strength of a CFCC are dependent on its inherent resistance to fracture, the presence of flaws, and any damage accumulation processes. These factors are affected by the composite material composition and variability in material and testing—components, reinforcement architecture and volume fraction, porosity content, matrix morphology, interface morphology, methods of material fabrication, test specimen preparation and conditioning, and surface condition.  
5.5 The results of tensile tests of test specimens fabricated to standardized dimensions from a particular material or selected portions of a part, or both, may...
SCOPE
1.1 This test method determines the axial tensile strength and stress-strain response of continuous fiber-reinforced advanced ceramic composite tubes at ambient temperature under monotonic loading. This test method is specific to tube geometries, because fiber architecture and specimen geometry factors are often distinctly different in composite tubes, as compared to flat plates.  
1.2 In the test method a composite tube/cylinder with a defined gage section and a known wall thickness is fitted/bonded into a loading fixture. The test specimen/fixture assembly is mounted in the testing machine and monotonically loaded in uniaxial tension at ambient temperature while recording the tensile force and the strain in the gage section. The axial tensile strength and the fracture strength are determined from the maximum applied force and the fracture force. The strains, the proportional limit stress, and the tensile modulus of elasticity are determined from the stress-strain data.  
1.3 This test method applies primarily to advanced ceramic matrix composite tubes with continuous fiber reinforcement: unidirectional (1D, filament wound and tape lay-up), bidirectional (2D, fabric/tape lay-up and weave), and tridirectional (3D, braid and weave). These types of ceramic matrix composites are composed of a wide range of ceramic fibers (oxide, graphite, carbide, nitride, and other compositions) in a wide range of crystalline and amorphous ceramic matrix compositions (oxide, carbide, nitride, carbon, graphite, and other compositions).  
1.4 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.  
1.5 The test method describes a range of test specimen tube geometries based on past tensile testing of ceramic composite tubes. These geometries are applicable to tubes with outer d...

General Information

• Status: Published
• Publication Date: 30-Jun-2021
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: C28 - Advanced Ceramics
• Drafting Committee: C28.07 - Ceramic Matrix Composites

Relations

• Refers: ASTM E251-20a - Standard Test Methods for Performance Characteristics of Metallic Bonded Resistance Strain Gages
• Effective Date: 01-Jun-2020
• Refers: ASTM E251-20 - Standard Test Methods for Performance Characteristics of Metallic Bonded Resistance Strain Gages
• Effective Date: 01-May-2020
• Refers: ASTM C1557-20 - Standard Test Method for Tensile Strength and Young's Modulus of Fibers
• Effective Date: 01-Jan-2020
• 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 C1239-13(2018) - Standard Practice for Reporting Uniaxial Strength Data and Estimating Weibull Distribution Parameters for Advanced Ceramics
• Effective Date: 01-Jul-2018
• Refers: ASTM C1273-18 - Standard Test Method for Tensile Strength of Monolithic Advanced Ceramics at Ambient Temperatures
• Effective Date: 01-Jul-2018
• Refers: ASTM D3878-18 - Standard Terminology for Composite Materials
• Effective Date: 01-Apr-2018
• 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 C1273-15 - Standard Test Method for Tensile Strength of Monolithic Advanced Ceramics at Ambient Temperatures
• Effective Date: 01-Jul-2015
• Refers: ASTM C1557-14 - Standard Test Method for Tensile Strength and Young’s Modulus of Fibers
• Effective Date: 15-Aug-2014
• Refers: ASTM E4-14 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2014
• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014

Overview

ASTM C1773-21 outlines the standard test method for assessing the monotonic axial tensile behavior of continuous fiber-reinforced advanced ceramic tubular test specimens at ambient temperature. Developed by ASTM Committee C28 on Advanced Ceramics, this method is crucial for measuring the uniaxial tensile properties-including tensile strength, fracture strength, stress-strain response, and elastic modulus-of ceramic matrix composite (CMC) tubes with continuous fiber reinforcements. The unique mechanical characteristics of such tubes necessitate direct tensile testing, as extrapolating from plate-based data is not accurate or reliable.

This standard provides vital data for material comparison, quality assurance, mechanical characterization, and design validation of ceramic composite tubes used in demanding applications, such as aerospace and high-temperature industrial settings.

Key Topics

• Scope and Applicability

  • Focused on tubes fabricated from advanced ceramic matrix composites with continuous fiber reinforcement (1D, 2D, 3D architectures).
  • Applicable to various fiber and matrix compositions including oxides, carbides, nitrides, graphite, and carbon.
  • Covers tube specimens with outer diameters from 10 to 150 mm and wall thicknesses of 1 to 25 mm.

• Test Methodology

  • Tubular specimens with defined gage sections and known wall thickness are installed into a loading fixture and subjected to monotonic uniaxial tension at ambient temperature.
  • Key properties measured include tensile strength, fracture strength, elastic modulus, proportional limit stress, and strain.
  • Requires specialized gripping and load train alignment to minimize bending stresses and ensure uniform axial loading.

• Significance of Direct Tubular Testing

  • The mechanical performance of CMC tubes is highly dependent on their fiber architecture and geometric configuration, which differ significantly from flat composites.
  • Testing provides data that cannot be accurately predicted from flat plate properties, especially for braided and 3D-woven tubes.
  • Results inform material development, comparative evaluation, and structural engineering design data generation.

• Data Collection and Reporting

  • Emphasizes consistent measurement of surface condition, morphology, and dimensions, and requires careful specimen preparation to control variables such as porosity and interface morphology.
  • Recommends using extensometers or strain gauges for strain measurement, with guidelines for instrumentation and data acquisition.
  • Stresses the importance of safe specimen handling due to potential hazards from brittle fracture.

Applications

• Material Development: Enables the evaluation of novel ceramic matrix composite (CMC) tubes' tensile behavior under realistic loading conditions, supporting R&D and optimization.
• Quality Assurance: Provides standardized data for batch qualification and process control in the manufacture of advanced ceramic tubes.
• Mechanical Characterization: Supplies critical mechanical property data necessary for structural analysis, finite element modeling, and predictive maintenance planning.
• Design Validation: Delivers direct insights into the performance of tubular geometries under service conditions, essential for industries where reliability under tensile stress is paramount, such as aerospace, power generation, and chemical processing.

Related Standards

Organizations working with advanced ceramics and composite test methods may also reference the following ASTM standards for related procedures and terminology:

• ASTM C1145: Terminology of Advanced Ceramics
• ASTM C1239: Practice for Reporting Uniaxial Strength Data and Weibull Distribution Parameters for Advanced Ceramics
• ASTM C1273: Test Method for Tensile Strength of Monolithic Advanced Ceramics at Ambient Temperatures
• ASTM C1557: Test Method for Tensile Strength and Young’s Modulus of Fibers
• ASTM D3878: Terminology for Composite Materials
• ASTM E4: Practices for Force Verification of Testing Machines
• ASTM E6 & E83: Mechanical Testing and Extensometer Verification

By adhering to ASTM C1773-21, manufacturers, researchers, and engineers can ensure reliable, repeatable tensile testing of advanced ceramic tubes, enabling informed decision-making and safer, higher-performing composite components in critical applications.

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.
Designation: C1773 − 21
Standard Test Method for
Monotonic Axial Tensile Behavior of Continuous Fiber-
Reinforced Advanced Ceramic Tubular Test Specimens at
Ambient Temperature
This standard is issued under the fixed designation C1773; 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* tubes. These geometries are applicable to tubes with outer
diametersof10to150mmandwallthicknessesof1to25mm,
1.1 This test method determines the axial tensile strength
where the ratio of the outer diameter-to-wall thickness (d /t)
O
and stress-strain response of continuous fiber-reinforced ad-
is typically between 5 and 30.
vanced ceramic composite tubes at ambient temperature under
monotonic loading. This test method is specific to tube 1.5.1 This test method is specific to ambient temperature
geometries, because fiber architecture and specimen geometry
testing.Elevatedtemperaturetestingrequireshigh-temperature
factors are often distinctly different in composite tubes, as
furnaces and heating devices with temperature control and
compared to flat plates.
measurement systems and temperature-capable grips and load-
ing fixtures, which are not addressed in this test method.
1.2 In the test method a composite tube/cylinder with a
defined gage section and a known wall thickness is fitted/
1.6 The test method addresses test equipment, gripping
bondedintoaloadingfixture.Thetestspecimen/fixtureassem-
methods, testing modes, allowable bending stresses,
bly is mounted in the testing machine and monotonically
interferences, tubular test specimen geometries, test specimen
loadedinuniaxialtensionatambienttemperaturewhilerecord-
preparation, test procedures, data collection, calculation, re-
ingthetensileforceandthestraininthegagesection.Theaxial
porting requirements, and precision/bias in the following
tensile strength and the fracture strength are determined from
sections.
the maximum applied force and the fracture force.The strains,
Section
the proportional limit stress, and the tensile modulus of
Scope 1
elasticity are determined from the stress-strain data.
Referenced Documents 2
Terminology 3
1.3 This test method applies primarily to advanced ceramic
Summary of Test Method 4
matrix composite tubes with continuous fiber reinforcement:
Significance and Use 5
Interferences 6
unidirectional (1D, filament wound and tape lay-up), bidirec-
Apparatus 7
tional (2D, fabric/tape lay-up and weave), and tridirectional
Hazards 8
(3D, braid and weave). These types of ceramic matrix com-
Test Specimens 9
posites are composed of a wide range of ceramic fibers (oxide, Test Procedure 10
Calculation of Results 11
graphite, carbide, nitride, and other compositions) in a wide
Report 12
range of crystalline and amorphous ceramic matrix composi-
Precision and Bias 13
Keywords 14
tions (oxide, carbide, nitride, carbon, graphite, and other
Annexes
compositions).
Interferences Annex A1
Test Specimen Geometry Annex A2
1.4 Thistestmethoddoesnotdirectlyaddressdiscontinuous
Grip Fixtures and Load Train Couplers Annex A3
fiber-reinforced, whisker-reinforced, or particulate-reinforced
Allowable Bending and Load Train Alignment Annex A4
ceramics, although the test methods detailed here may be
Test Modes and Rates Annex A5
equally applicable to these composites.
1.7 Units—The values stated in SI units are to be regarded
1.5 The test method describes a range of test specimen tube
as standard.
geometries based on past tensile testing of ceramic composite
1.8 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
This test method is under the jurisdiction of ASTM Committee C28 on
Advanced Ceramics and is the direct responsibility of Subcommittee C28.07 on responsibility of the user of this standard to establish appro-
Ceramic Matrix Composites.
priate safety, health, and environmental practices and deter-
CurrenteditionapprovedJuly1,2021.PublishedJuly2021.Originallyapproved
mine the applicability of regulatory limitations prior to use.
in 2013. Last previous edition approved in 2017 as C1773–17. DOI: 10.1520/
C1773-21. Specific precautionary statements are given in Section 8.
*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
C1773 − 21
1.9 This international standard was developed in accor- 3.1.4 bending strain, n—the difference between the strain at
dance with internationally recognized principles on standard- the surface and the axial strain. In general, the bending strain
ization established in the Decision on Principles for the variesfrompointtopointaroundandalongthereducedsection
Development of International Standards, Guides and Recom- of the test specimen. E1012
mendations issued by the World Trade Organization Technical
3.1.5 ceramic matrix composite, n—a material consisting of
Barriers to Trade (TBT) Committee.
two or more materials (insoluble in one another) in which the
major,continuouscomponent(matrixcomponent)isaceramic,
2. Referenced Documents
whilethesecondarycomponent/s(reinforcingcomponent)may
2.1 ASTM Standards:
be ceramic, glass-ceramic, glass, metal, or organic in nature.
C1145Terminology of Advanced Ceramics
These components are combined on a macroscale to form a
C1239Practice for Reporting Uniaxial Strength Data and
useful engineering material possessing certain properties or
Estimating Weibull Distribution Parameters forAdvanced
behavior not possessed by the individual constituents. C1145
Ceramics
3.1.6 continuous fiber-reinforced ceramic matrix composite
C1273Test Method for Tensile Strength of Monolithic
(CFCC), n—aceramicmatrixcompositeinwhichthereinforc-
Advanced Ceramics at Ambient Temperatures
ing phase consists of a continuous fiber, continuous yarn, or a
C1557TestMethodforTensileStrengthandYoung’sModu-
woven fabric. C1145
lus of Fibers
D3878Terminology for Composite Materials 3.1.7 fracture (breaking) force, P ,n—the force at
fracture
which the test specimen ruptures, breaking into two or more
D5450Test Method for Transverse Tensile Properties of
Hoop Wound Polymer Matrix Composite Cylinders pieces.
E4Practices for Force Verification of Testing Machines
3.1.8 fracture strength, S,n—the tensile stress at which the
f
E6Terminology Relating to Methods of Mechanical Testing
test specimen ruptures, breaking into two or more pieces or
E83Practice for Verification and Classification of Exten-
where the applied force drops off significantly. Typically, a
someter Systems
10% force drop off is considered significant.
E122PracticeforCalculatingSampleSizetoEstimate,With
3.1.9 gage length, l ,n—the original length of that portion
O
Specified Precision, the Average for a Characteristic of a
of the test specimen over which strain or change of length is
Lot or Process
determined. E6
E177Practice for Use of the Terms Precision and Bias in
3.1.10 matrix cracking stress, n—theappliedtensilestressat
ASTM Test Methods
which the matrix in the composite cracks into a series of
E251Test Methods for Performance Characteristics of Me-
roughly parallel blocks normal to the tensile stress.
tallic Bonded Resistance Strain Gages
E337Test Method for Measuring Humidity with a Psy-
3.1.10.1 Discussion—In some cases, the matrix cracking
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
stress may be indicated on the stress-strain curve by deviation
peratures)
from linearity (proportional limit) or incremental drops in the
E691Practice for Conducting an Interlaboratory Study to
stress with increasing strain. In other cases, especially with
Determine the Precision of a Test Method
materials which do not possess a linear portion of the stress-
E1012Practice for Verification of Testing Frame and Speci-
strain curve, the matrix cracking stress may be indicated as the
men Alignment Under Tensile and Compressive Axial
first stress at which a permanent offset strain is detected in the
Force Application
unloading stress-strain (elastic limit).
3. Terminology 3.1.11 modulus of elasticity, E, n—the ratio of stress to
corresponding strains below the proportional limit. E6
3.1 Definitions:
3.1.12 modulus of resilience, U,n—strain energy per unit
3.1.1 Pertinent definitions, as listed in Terminology C1145,
r
volume required to elastically stress the material from zero to
Practice E1012,Terminology D3878, andTerminology E6, are
the proportional limit indicating the ability of the material to
shown in the following with the appropriate source in bold
absorb energy when deformed elastically and return it when
type. Additional terms used in conjunction with this test
unloaded.
method are defined in the following:
3.1.2 advanced ceramic, n—a highly engineered, high-
3.1.13 modulus of toughness, U,n—strain energy per unit
t
performance, predominantly nonmetallic, inorganic, ceramic
volume required to stress the material from zero to final
material having specific functional attributes. C1145
fracture indicating the ability of the material to absorb energy
3.1.3 axial strain, n—the average of the longitudinal strains beyond the elastic range (that is, damage tolerance of the
material).
measured at the surface on opposite sides of the longitudinal
axis of symmetry of the test specimen by two strain-sensing
3.1.13.1 Discussion—Themodulusoftoughnesscanalsobe
deviceslocatedatthemidlengthofthereducedsection. E1012
referred to as the cumulative damage energy and as such is
regardedasanindicationoftheabilityofthematerialtosustain
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
damage rather than as a material property. Fracture mechanics
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
methods for the characterization of CFCCs have not been
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. developed. The determination of the modulus of toughness as
C1773 − 21
provided in this test method for the characterization of the continuous nonstop test rate with no reversals from test
cumulative damage process in CFCCs may become obsolete initiation to final fracture.
when fracture mechanics methods for CFCCs become avail-
4.3 This test method is applicable to a range of test cylinder
able.
specimen geometries and sizes, which are described and
3.1.14 proportional limit stress, σ ,n—the greatest stress
o
considered in Section 9.Asingle fixed test specimen geometry
that a material is capable of sustaining without any deviation
cannot be defined because there is a wide range of composite
from proportionality of stress to strain (Hooke’s law). E6
cylinder configurations in use and development. The different
described test specimen geometries are typically applicable to
3.1.14.1 Discussion—Many experiments have shown that
tubes with outer diameters of 10 to 150mm and wall thick-
valuesobservedfortheproportionallimitvarygreatlywiththe
nesses of 1 to 25 mm, where the ratio of the outer diameter-
sensitivity and accuracy of the testing equipment, eccentricity
to-wall thickness (d /t) is between 5 and 30.
O
of loading, the scale to which the stress-strain diagram is
plotted, and other factors. When determination of proportional
5. Significance and Use
limit stress is required, the procedure and sensitivity of the test
equipment should be specified.
5.1 This test method provides information on the uniaxial
tensilepropertiesandtensilestress-strainresponseofaceramic
3.1.15 percent bending, n—the bending strain times 100
divided by the axial strain. E1012 composite tube—tensile strength and strain, fracture strength
and strain, proportional limit stress and strain, tensile elastic
3.1.16 slow crack growth, n—subcritical crack growth (ex-
modulus, etc. The information may be used for material
tension) which may result from, but is not restricted to, such
development, material comparison, quality assurance,
mechanisms as environmentally assisted stress corrosion or
characterization, and design data generation.
diffusive crack growth. C1145
5.2 Continuous fiber-reinforced ceramic composites
3.1.17 stress corrosion, n—environmentally induced degra-
(CFCCs)arecomposedofcontinuousceramic-fiberdirectional
dationthatresultsintheformationandgrowthofcracksand/or
(1D, 2D, and 3D) reinforcements in a fine-grain-sized
damage in glasses and many ceramics when subjected to the
(<50µm) ceramic matrix with controlled porosity. Often these
combined action of a corroding agent and stress. C1145
composites have an engineered thin (0.1 to 10µm) interface
coating on the fibers to produce crack deflection and fiber
3.1.17.1 Discussion—Such environmental effects com-
monlyincludetheactionofmoisture,aswellasothercorrosive pull-out. These ceramic composites offer high-temperature
stability, inherent damage tolerance, and high degrees of wear
species, often with strong temperature dependence.
and corrosion resistance. As such, these ceramic composites
3.1.18 tensile strength, S ,n—the maximum tensile stress
u
are particularly suited for aerospace and high-temperature
which a material is capable of sustaining. Tensile strength is
structural applications (1, 2).
calculated from the maximum force during a tension test
carried to rupture and the original cross-sectional area of the
5.3 CFCC components have a distinctive and synergistic
test specimen. E6
combinationofmaterialproperties,interfacecoatings,porosity
control,compositearchitecture(1D,2D,and3D),andgeomet-
3.1.19 tow, n—in fibrous composites, a continuous, ordered
ric shape that are generally inseparable. Prediction of the
assemblyofessentiallyparallel,collimatedfilaments,normally
mechanical performance of CFCC tubes (particularly with
without twist and of continuous filaments. D3878
braidand3Dweavearchitectures)cannotbemadebyapplying
3.1.20 uniaxial tension, n—the application of tensile force
measured properties from flat CFCC plates to the design of
coaxially with the long dimension of the test specimen.
tubes. Direct uniaxial tensile strength tests of CFCC tubes are
needed to provide reliable information on the mechanical
4. Summary of Test Method
behavior and strength of tube geometries.
4.1 This test method involves the testing of a ceramic
5.4 CFCCs generally experience “graceful” fracture from a
composite tube/cylinder with a known wall thickness in
cumulative damage process, unlike monolithic advanced ce-
monotonic uniaxial tension at ambient temperature. The pre-
ramics which fracture catastrophically from a single dominant
paredtestspecimenwithadefinedgagesectionisfitted/bonded
flaw. The tensile behavior and strength of a CFCC are
into a loading fixture and the test specimen/fixture assembly is
dependentonitsinherentresistancetofracture,thepresenceof
mounted in the testing machine.The test specimen is loaded in
flaws, and any damage accumulation processes. These factors
axial tension while recording the applied force and resulting
are affected by the composite material composition and vari-
strain. The axial tensile strength S and the fracture strength S
u f
ability in material and testing—components, reinforcement
are determined from the maximum applied force and the
architecture and volume fraction, porosity content, matrix
fracture force. The axial strains, the proportional limit stress,
morphology, interface morphology, methods of material
and the tensile modulus of elasticity are determined from the
fabrication, test specimen preparation and conditioning, and
stress-strain response data.
surface condition.
4.2 Tensile strength as used in this test method refers to the
tensile strength obtained under monotonic uniaxial loading. In
uniaxial loading, the force is applied coaxially with the long
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
dimension of the tube test specimen. Monotonic refers to a this standard.
C1773 − 21
5.5 The results of tensile tests of test specimens fabricated 7.1.1 Fixed Member—A fixed or essentially stationary
to standardized dimensions from a particular material or member to which one end of the tension specimen/fixture
selected portions of a part, or both, may not totally represent assembly can be attached.
the strength and deformation properties of the entire, full-size 7.1.2 Movable Member—A movable member to which the
end product or its in-service behavior in different environ-
opposite end of the tension specimen/fixture assembly can be
ments. attached.
7.1.3 Drive Mechanism,forimpartingtothemovablemem-
5.6 For quality control purposes, results derived from stan-
ber a uniform controlled velocity with respect to the fixed
dardized tubular tensile test specimens may be considered
member,thisvelocitytoberegulatedasspecifiedin10.2.4and
indicativeoftheresponseofthematerialfromwhichtheywere
Annex A5.
taken, given primary processing conditions and post-
7.1.4 Force/Load Measurement—A suitable force measure-
processing heat treatments.
ment device capable of showing the total tensile force carried
6. Interferences by the test specimen. This device shall be essentially free of
inertia lag at the specified rate of testing and shall indicate the
6.1 Interferences in the testing of ceramic composite tubes
applied force with an accuracy of 61 % or better within the
arise from nine factors—material variability, dimensional vari-
selectedforcerangeofthetestingmachine.Theaccuracyofthe
ability in the test specimen, test specimen size and volume
force measurement device shall be verified in accordance with
effects, surface condition variability, fabrication effects, mis-
Practices E4.
alignment and bending stresses, gripping and bonding failures,
7.1.5 Construction Materials—The fixed member, movable
test environment variability, and out-of-gage failures. All of
member, drive mechanism, load train, and fixtures shall be
these factors have to be understood and controlled for valid
constructed of such materials and in such proportions that the
tests. These interference factors are discussed in detail in
total system compliance of the system contributed by these
Annex A1.
parts is minimized.
7. Apparatus
7.2 Gripping Fixtures—Various types of gripping devices
7.1 Tensile Testing Machine, comprised of the following may be used to transmit the measured force applied by the
components and illustrated schematically in Fig. 1. testing machine to the tubular test specimens. Because of the
FIG. 1 Tensile Test Apparatus
C1773 − 21
brittle nature of the matrices of CFCCs, gripping devices must 7.2.4.1 This verification of the alignment and maximum
have a uniform, continuous contact with the entire gripped percent bending shall be conducted at a minimum at the
section of the tubular test specimen. (Line contact, point beginning and end of each test series. Annex A4 provides
contacts, and nonuniform pressure can produce Hertizan-type additionaldetailsonbendingissuesandalignmentmethodsfor
stresses leading to crack initiation and fracture of the test
CFCCs,alongwithadetailedprocedureforverificationofload
specimen in the gripped section.) Gripping devices can be train alignment, based on Practice E1012.
classed generally as those employing active grip fixtures and
7.2.4.2 The recommended maximum allowable percent
those employing passive grip interfaces as discussed in the
bending at the onset of the cumulative fracture process (for
following section and in Annex A3.
example, matrix cracking stress) for composite test specimens
7.2.1 Active Grip Fixtures—Active grip interfaces use the
in this test method is 5 %.
direct application of a normal gripping force (through
7.3 Strain Measurement—Strain should be determined by
mechanical, hydraulic, or pneumatic action) to the grip section
means of either a suitable extensometer or bonded resistance
of the test specimen. These active grips commonly use split
strain gages. If Poisson’s ratio is to be determined, the tubular
circularcolletsthatencircletheoutercircumferenceofthetube
test specimen must be instrumented to measure strain in both
and grip the tube through a lateral or wedging action. This
axial and circumferential directions.
gripping action transmits the uniaxial force applied by the test
7.3.1 Extensometers—Extensometers used for tensile test-
machine by friction between the collet faces and the tubular
ing of CFCC tubular test specimens shall satisfy Practice E83,
test specimen. Examples, descriptions, and design/use factors
ClassB-1requirements.Extensometersarerecommendedtobe
for active grips are discussed in A3.1.
used in place of strain gages for test specimens with gage
7.2.2 Passive Grip Fixtures—Passive grip interfaces trans-
lengths >25 mm and shall be used for high-deformation tests
mit the force applied by the test machine to the tubular test
beyondthestrainrangeofstraingages.Extensometersshallbe
specimen through a direct adhesive bond into the grips or by
calibrated periodically in accordance with Practice E83. For
mechanical action between geometric features on the test
extensometers mechanically attached to the test specimen, the
specimen and the grip fixture. Examples, descriptions, and
attachment should be such as to cause no damage to the
design/use factors for passive grips are discussed in A3.3.
specimen surface. In addition, the weight of the extensometer
7.2.3 Load Train Couplers—Various types of devices (load
should be supported so as not to introduce bending stresses in
train couplers) may be used to attach the active or passive grip
the test specimen greater than those allowed in 7.2.4.2.
assemblies to the testing machine. The load train couplers in
7.3.2 Strain Gages—Although extensometers are com-
conjunction with the type of gripping device play major roles
monly used for CFCC strain measurement, strain can also be
in the alignment of the load train and minimizing any extra-
determined with bonded resistance strain gages and suitable
neous bending stresses imposed in the test specimen. Load
strain recording equipment. The strain gages, surface
train couplers can be classified generally as fixed and nonfixed
preparation, and bonding agents should be chosen to provide
and are discussed in A3.6.
adequate performance on the subject materials. Gage calibra-
7.2.3.1 Fixed Load Train Couplers—Fixed couplers usually
tion certification shall comply with Test Methods E251.A
employ concentricity (x,y alignment) and angularity adjusters
general reference on strain gages for composites is Tuttle and
to minimize load train misalignments. With fixed load train
Brinson (3). Some guidelines on the use of strain gages on
couplers, alignment verification must be performed as dis-
ceramic composites are as follows.
cussed in 7.2.4 and Annex A4.
7.3.2.1 Strain Gage Length—Unless it can be shown that
7.2.3.2 Fixed load train couplers are preferred in monotonic
strain gage readings are not unduly influenced by localized
testingofCFCCsbecausetheymaintainauniformstressacross
strain events such as fiber crossovers, strain gages should not
the composite when localized deformation occurs in the test
be less than 9 to 12 mm in length for the longitudinal direction
specimen.
and not less than 6 mm in length for the transverse direction.
7.2.3.3 Nonfixed Load Train Couplers—Nonfixed couplers
Whentestingwovenfabriccomposites,thestraingagesshould
produce self-alignment of the load train during the movement
have an active gage length that is at least as great as the
of the crosshead. Generally the coupling devices rely upon
characteristic unit cell (repeating unit) of the weave; this
freely moving linkages to eliminate applied moments as the
averages the localized strain effects of the fiber crossovers.
load train components are loaded. Knife edges, universal
7.3.2.2 Surface Preparation—Many CFCCs have high de-
joints, hydraulic couplers, or air bearings are examples of such
devices. The operation of the nonfixed couplers must be grees (>5 %) of porosity and surface roughness and therefore
require surface preparation (such as surface filling with epoxy)
verified for allowable bending as discussed in7.2.4 and Annex
A4. before the strain gages can be applied and fully bonded to the
surface. Reinforcing fibers in the composite should not be
7.2.4 Allowable Bending and Load Train Alignment—
exposed or damaged during the surface preparation process.
Extraneous and excessive bending stresses from misalignment
inuniaxialtensiletestscancauseorpromotenonuniformstress 7.3.2.3 Temperature Considerations—Consideration of
distributions and premature failure. These bending stresses are some form of temperature compensation for the strain gages is
minimized by aligning the load train for concentricity and recommended, even when testing at standard laboratory atmo-
angularity. The tensile test load train shall be properly aligned sphere. Temperature compensation is required when testing in
and verified in all tests. nonambient temperature environments.
C1773 − 21
7.3.2.4 Transverse Sensitivity—Consideration should be nature of advanced ceramics and the release of strain energy
given to the transverse sensitivity of the selected strain gage/s. contribute to the potential release of uncontrolled fragments
This is particularly important for a transversely mounted gage upon fracture. Means for containment and retention of these
used to determine Poisson’s ratio, because composites often fragments for later reconstruction and fractographic analysis is
have markedly different moduli in different directions in the highly recommended. (Plastic shields can be used to encircle
fiber architecture. The strain gage manufacturer should be the test fixture and to capture specimen fragments.)
consulted for recommendations on transverse sensitivity cor-
8.2 Exposed fibers at the edges of CFCC test specimens
rections and effects on composites.
present a hazard due to the sharpness and brittleness of the
7.3.2.5 Poisson’s ratio is easily determined with biaxial (0°
ceramic fiber. All those required to handle these materials
to90°)straingagerosetteswhichmeasurethestraininboththe
should be well informed of such conditions and the proper
axial and circumferential directions.
handling techniques.
7.3.3 Data Acquisition—At the minimum, an autographic
record of applied tensile force and gage section elongation (or
9. Test Specimens
strain) versus time should be obtained. Either analog chart
9.1 Geometry Considerations—CFCC tubes are fabricated
recorders or digital data acquisition systems can be used for
in a wide range of sizes and geometries and across a wide
thispurpose,althoughadigitalrecordisrecommendedforease
spectrum of different reinforcement fibers, distinctive ceramic
of later data analysis.
matrix materials, and markedly different fabrication methods.
7.3.3.1 Recording devices shall be accurate to within
In addition, the fiber architecture for CFCC tubes has a broad
60.1% for the entire testing system including readout unit as
range of configurations with different fiber loadings and
specified in Practices E4 and shall have a minimum data
directional variations. It is currently not practical to define a
acquisition rate of 10 Hz, with a response of 50 Hz deemed
single test specimen geometry that is applicable to all CFCC
more than sufficient.
tubes.
7.3.3.2 Strain or elongation of the gage section, or both,
should be recorded either similarly to the force or as indepen-
9.2 The selection and definition of a tubular test specimen
dent variables of force. Crosshead displacement of the test
geometry depends on the purpose of the tensile testing effort.
machinemayalsoberecordedbutshouldnotbeusedtodefine
For example, if the tensile strength of an as-fabricated compo-
displacement or strain in the gage section, especially when
nentwithadefinedgeometryisrequired,thedimensionsofthe
self-aligning couplers are used in the load train.
resulting tensile specimen may reflect the wall thickness, tube
7.3.4 Dimension Measurement Devices—Ball or anvil-type
diameter, and length restrictions of the component. If it is
micrometers should be used for measuring the test specimen
desired to evaluate the effects of interactions of various
inner and outer diameters, to an accuracy of 0.02 mm or 1 %
constituentmaterialsforaparticularCFCCmanufacturedviaa
of the measured dimension, whichever is greater. Flat, anvil-
particular processing route, then the size of the test specimen
type micrometer or calipers of similar resolution may be used
and resulting gage section will reflect the size and geometry
for measuring the overall test specimen length and the defined
limits of that processing method. In addition, grip devices and
gage length.
load train couplers (as discussed in Section 7 and Annex A3)
7.3.5 Conditioning Chamber—When conditioning CFCC
will influence the final design of the test specimen geometry.
materials at non-ambient environments, an environmental con-
9.3 Test Specimen Dimensions—This test method is gener-
ditioning chamber with a controlled temperature and humidity
ally applicable to tubes with outer diameters of 10 to 150 mm
levelsisrequired.Thechambershallbecapableofmaintaining
andwallthicknessesof1to25mm,wheretheratiooftheouter
the required temperature to within 63°C and the required
diameter-to-wall thickness (d /t) is commonly between 5 and
O
relative humidity level to within 65 %. Chamber conditions
30.
shall be monitored either on an automated continuous basis or
9.4 Test Specimen Geometries—Tubular test specimens are
on a manual basis at regular intervals.
classified into two groups—straight-sided specimens and con-
7.3.6 Environmental Test Chamber—Whentestingmaterials
toured gage specimens, as shown in Figs. 2 and 3. Contour
at other than ambient laboratory conditions (high/low
gage specimens are distinctive in having gage sections with
humidity, high/low temperatures, or both), the environmental
thinner wall thicknesses than the gripping sections. Both types
chambershallbecapableofmaintainingthegagesectionofthe
of test specimens can be used in active and passive grips.
test specimen at the required temperature to within 63°Cor
9.4.1 Annex A2 provides different examples of straight-
the required relative humidity level to within 65 %, or both.
sided and contoured gage test specimen tube geometries along
Chamber conditions shall be monitored during the test either
with geometry, design, fabrication, and preparation informa-
on an automated continuous basis or on a manual basis at
tion. However, any CFCC tube geometry is acceptable if
regular intervals.
fracture failure occurs consistently in the designated gage
7.3.7 Calibration and Standardization—The accuracy of all
section with minimal extraneous bending stresses. Deviations
measuring equipment shall have certified calibrations that are
fromtheexamplegeometriesarepermitteddependinguponthe
current at the time the equipment is used.
particular CFCC tube being evaluated.
8. Hazards
9.4.2 Although straight-sided tubular test specimens are
8.1 Duringtheconductofthistestmethod,thepossibilityof easiertofabricateandarecommonlyused,tubetestspecimens
flying fragments of broken test material is high. The brittle with contoured gage sections are preferred to promote tensile
C1773 − 21
9.7 Dimensional Tolerances and Variability—Dimensional
tolerances will depend on the specific selected specimen
geometry, the method of manufacturing, and the performance
requirementsoftheCFCCapplication.ItiscommonforCFCC
tubes to have significant diametral variability (1 to 5 mm) in
the as-fabricated condition, particularly for larger diameter
tubes. The gage section may or may not be machined to a
specific tolerance (A2.7). Any significant (>2 %) dimensional
variability in the OD and ID should be determined and
recorded.
9.8 Nondestructive evaluation (ultrasonics, thermal
imaging, computerized tomography, etc.) may be used to
assess internal morphology (delaminations, porosity
FIG. 2 Schematic of Straight-Sided Tube Specimen
concentrations, etc.) in the composite. Record these
observations/measurements and the results of any nondestruc-
tive evaluations and include them in the final report.
9.9 Surface Measurement—Insomecasesitisdesirable,but
not required, to measure surface roughness in the gage section
to quantify the surface condition. Methods such as contacting
profilometry can be used to determine surface roughness
parallel and perpendicular to the tensile axis across a sufficient
area to adequately characterize the surface. When measured,
surface roughness should be reported.
9.10 Test Specimen Storage and Handling—Care should be
exercised in handling, packaging, and storage of finished test
specimens to avoid the introduction of random surface flaws.
In addition, attention should be given to pre-test storage of test
specimens in controlled environments or desiccators to avoid
unquantifiable environmental (for example, humidity) degra-
FIG. 3 Schematic of Contoured Gage Section Tube Specimen
dation of test specimens prior to testing.
failure in the uniformly stressed gage section. The contoured 10. Test Procedure
gagesectionsareformedbyintegralthick-wallgripsectionsin
10.1 Any deviation from this test method shall be described
the composites or by adhesively bonded collars/sleeves in the
in detail in the test report.
grip sections (Annex A2). A key factor in contoured gage
10.2 Test Plan Parameters and Factors—The following test
section specimens is the minimizing of any stress concentra-
specimen parameters and experimental test factors have to be
tions at the geometric transitions into the gage sections.
defined in detail as part of the test plan.
9.5 Baseline Fabrication—The composition, architecture,
10.2.1 The test specimen geometry, sampling method, test
and fabrication processing of the CFCC composite must be
specimen preparation procedure, and any environmental con-
well defined and suitably controlled to produce components
ditioning or test parameters (temperature, humidity, time), or
and test specimens with acceptable, repeatable, and uniform
combinations thereof.
physical and mechanical properties. The composition, fiber
10.2.2 The desired tensile properties and the data reporting
architecture, fabrication processing, and lot identification
format.
should be fully determined and documented.
10.2.3 An estimate of the tensile properties for the CFCC
9.6 Test Count and Test Specimen Sampling—A minimum being tested (tensile strength and strain, modulus of elasticity,
of five valid test specimens is required for the purposes of etc.). This information is used to determine the required
estimating a mean/average. A greater number of valid test capabilities and range of the test apparatus—load frame, load
specimens may be necessary if estimates regarding the form of cells, grips, extensometers, strain gages, etc.
the strength distribution are required. The procedures outlined 10.2.4 Test modes and rates can have distinct and strong
inPracticeE122shouldbeusedtoestimatethenumberoftests influences on fracture behavior of advanced ceramics, even at
needed for determining a mean with a specified precision. If ambient temperatures, depending on test environment or con-
material cost or test specimen availability limits the number of dition of the test specimen. Test modes may involve force,
possible tests, fewer tests can be conducted to determine an displacement, or strain control. Recommended rates of testing
indication of material properties. Test specimens should be are intended to be sufficiently rapid to obtain the maximum
selected and prepared from representative CFCC samples that possible tensile strength at fracture of the material. Typically,
meet the stated testing objectives and requirements. The fracture should occur within 5 to 60 s after the start of the test.
method of sampling shall be reported. Annex A5 describes the different test modes and provides
C1773 − 21
guidance on how to choose a test mode and rate. In all cases, 10.4 Test Specimen Assembly/Fixturing—Twotestspecimen
the test mode and rate must be reported. factors have to be considered in specimen assembly/
fixturing—the use of end plugs and the method of adhesive
10.2.5 The method of strain measurement (extensometer,
strain gauge, or both) and the strain measurement plan (type bonding.
and gage length of extensometer, type and number of strain
10.4.1 End Plugs—End plugs may be used in active grip-
gauges, locations/positions, and control/measurement system)
ping to prevent collapse in the grip sections. If end plugs
should be noted and reported.
(A3.2) are being used in the test (for active gripping), insert
and bond the two end plugs into the test specimen, using the
10.3 Test Specimen Preparation—Test specimen prepara-
designated adhesive and alignment procedure. Ensure that the
tion consists of three steps—conditioning, measurement, and
end plugs are centered in the test specimen and at the proper
strain gauge installation (if used).
depth. Cure the adhesive per the manufacturer’s specifications.
10.3.1 Conditioning—Condition the test specimens at the
desired temperature, humidity, and time, per the test plan. 10.4.2 Adhesive Bonding into the Grip Fixtures—If adhe-
sive bonding grip fixtures are being used (AnnexA3), the test
10.3.2 Test Specimen Measurement—Conduct 100 %
inspection/measurements of all test specimens for surface specimen should be secured into the two end fixtures by filling
thefixturecavitieswiththeadhesivematerial(preparedperthe
condition (cracks, surface flaws, surface porosity, etc.). Note
that the frequency of valid gage section fractures and minimal manufacturer’s instructions). Position the test specimen into
thetwogripfixturesanduseanalignmentfixturetoensurethat
bending in the gage section are dependent on test specimen
dimensions being within the desired tolerances. the two end fixtures and the test specimen are aligned concen-
10.3.2.1 Measure the outer diameter (d ), the internal di- trically. Cure the adhesive per the manufacturer’s specifica-
O
tions. After curing, measure the free length/distance between
ameter (d), or the wall thickness (t), or both, of the gage
i
section of each test specimen to within 0.02 mm or 1% of the the end fixtures at four points at 90° intervals around the
specimen/fixture circumference. Significant deviations (>2 %)
measured dimension, whichever is greater. Make three mea-
surements around the circumference on at least three different in the measured length are an indication of test specimen or
cross-sectional planes along the length of the gage section. grip section misalignment.
Record and report the measured dimensions and locations of
10.5 Load Train Alignment and Bending Stress
themeasurementsforuseinthecalculationofthetensilestress.
Assessment—If load train alignment is done with a “dummy”
Use the average of the multiple measurements in the stress
specimen, adjust/verify the alignment of the load train, per the
calculations [d = d –2t].
i o
guidance in 7.2.4 and Annex A4.
10.3.2.2 To avoid damage in the gage section area it is
recommended that these measurements be made either opti- 10.6 Test Specimen Insertion—Each grip system and test
cally (for example, an optical comparator) or mechanically specimen geometry (as described in Section 7, AnnexA2, and
using a self-limiting (friction or ratchet mechanism) flat, Annex A3) will require a unique procedure for mounting the
anvil-type micrometer with anvil diameter of at least 5 mm. In
test specimen in the load train. If special fixture components
all cases the resolution of the instrument shall be as specified are required for each test, these should be identified and noted
in 7.3.4.
in the test report.
10.3.2.3 Exercise caution to prevent damage to the test
10.6.1 Mount the test specimen/assembly into the grips and
specimen gage section. Ball-tipped micrometers may be pre-
load train, ensuring that the test specimen is properly posi-
ferred when measuring test specimens with rough or uneven
tioned and aligned in the grips. Tighten the grips evenly and
nonwoven surfaces.
firmly to the degree necessary to prevent slippage of the test
10.3.2.4 Alternatively, to avoid damage to the gage section
specimen during the test but not to the point where the
(or in cases where it is not possible to infer or determine gage
specimen would be crushed.
section wall thickness), use the procedures described in 10.13
10.6.2 Ifstraingagesareusedtomonitorbending,thestrain
to make post-fracture measurements of the gage section
gages should be zeroed with the test specimen attached at only
dimensions. Note that in some cases, the fracture process can
oneend,sothatitishangingfree.Thiswillensurethatbending
severelyfragmentthegagesectionintheimmediatevicinityof
due to the grip closure is factored into the measured bending.
the fracture, thus making post-fracture measurements of di-
10.6.3 If load train alignment is done with the actual test
mensions difficult. In these cases, it is advisable to do pre-test
specimen, adjust/verify the alignment of the load train, per the
measurements per 10.3.2 to ensure reliable measurements.
guidance in 7.2.4 and Annex A4.
10.3.2.5 Measure and record the overall length of the test
10.6.4 Markthetestspecimenwithanindeliblemarkerasto
specimen and the length of the gage section, if it is defined.
top and bottom and front (side facing the operator) in relation
10.3.2.6 If needed, measure the surface finish of the gage
to the test machine. In the case of strain-gaged test specimens,
section of the test specimens using a suitable method (see 9.7).
orient the test specimen such that the “front” of the test
10.3.3 Strain Gage Installation—Attach strain gages to the
specimen and a unique strain gage coincide (for example,
test specimen per the strain measurement test plan, ensuring
Strain Gage 1, designated SG1).
that strain gages are properly oriented and securely bonded to
the test specimen per the manufacturer’s instructions. (Strain 10.7 Extensometers and Strain Gages—Mount/connect the
gage installation can also be done after the test specimen is extensometer/s on the test specimen, if an extensometer is
bonded into the grip fixtures.) being used. Connect the lead wires of any strain gages to the
C1773 − 21
conditioning equipment and allow the strain gages to equili- at least equal to that calculated by Eq 4 was sustained in the
brate under power for at least 30 min prior to conducting the uniform gage section before the test was prematurely termi-
verification tests. This will minimize drift during the test. nated by a non-gage section fracture) as discussed in Practice
C1239 for the determination of estimates of the strength
10.8 Test Environment—Ifanenvironmentaltestchamberis
distribution parameters. From a conservative standpoint, in
beingused,conditionthetestspecimenatthedefinedtempera-
completing a required statistical sample (for example,N=5)
tureandhumidityforthedesignatedperiodoftime.Recordthe
for purposes of average strength, test one replacement test
environmental conditions and the “time to equilibrium” for
specimenforeachtestspecimenthatfracturesoutsidethegage
each test.
section.
10.9 Testing Machine Setup—Activateandadjustthetesting
10.12.2 A significant fraction (>10 %) of invalid or cen-
machine for initial crosshead position, zero load, and desired
soredfailures(orboth)inasamplepopulationshallbecauseto
test mode and test rate. Set the mode and speed of testing so
re-examine the means of force introduction into the material.
that the failure occurs in less than 60 s, using the guidance in
Factors of concern that can produce invalid tests include the
Annex A5.
alignment of the test specimen in the fixture, alignment of the
10.10 Data Collection Equipment—Assemble and activate fixtures in the grips, collar materials, and the adhesive used to
the data recording instrumentation for force and strain, setting bond the test specimen to the fixture.
the range, sensitivity, and recording/data collection rate.
10.13 Post-Test Measurement and Analysis:
10.11 The tensile test is conducted in the following se-
10.13.1 Dimensions—Measure and report the
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C1773 − 17 C1773 − 21
Standard Test Method for
Monotonic Axial Tensile Behavior of Continuous Fiber-
Reinforced Advanced Ceramic Tubular Test Specimens at
Ambient Temperature
This standard is issued under the fixed designation C1773; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 This test method determines the axial tensile strength and stress-strain response of continuous fiber-reinforced advanced
ceramic composite tubes at ambient temperature under monotonic loading. This test method is specific to tube geometries, because
fiber architecture and specimen geometry factors are often distinctly different in composite tubes, as compared to flat plates.
1.2 In the test method a composite tube/cylinder with a defined gage section and a known wall thickness is fitted/bonded into a
loading fixture. The test specimen/fixture assembly is mounted in the testing machine and monotonically loaded in uniaxial tension
at ambient temperature while recording the tensile force and the strain in the gage section. The axial tensile strength and the
fracture strength are determined from the maximum applied force and the fracture force. The strains, the proportional limit stress,
and the tensile modulus of elasticity are determined from the stress-strain data.
1.3 This test method applies primarily to advanced ceramic matrix composite tubes with continuous fiber reinforcement:
uni-directional (1-D,unidirectional (1D, filament wound and tape lay-up), bi-directional (2-D,bidirectional (2D, fabric/tape lay-up
and weave), and tri-directional (3-D,tridirectional (3D, braid and weave). These types of ceramic matrix composites are composed
of a wide range of ceramic fibers (oxide, graphite, carbide, nitride, and other compositions) in a wide range of crystalline and
amorphous ceramic matrix compositions (oxide, carbide, nitride, carbon, graphite, and other compositions).
1.4 This test method does not directly address discontinuous fiber-reinforced, whisker-reinforcedwhisker-reinforced, or
particulate-reinforced ceramics, although the test methods detailed here may be equally applicable to these composites.
1.5 The test method describes a range of test specimen tube geometries based on past tensile testing of ceramic composite tubes.
These geometries are applicable to tubes with outer diameters of 10 to 150 mm and wall thicknesses of 1 to 25 mm, where the
ratio of the outer diameter-to-wall thickness (d /t) is typically between 5 and 30.
O
1.5.1 This test method is specific to ambient temperature testing. Elevated temperature testing requires high temperature
high-temperature furnaces and heating devices with temperature control and measurement systems and temperature-capable grips
and loading fixtures, which are not addressed in this test method.
1.6 The test method addresses test equipment, gripping methods, testing modes, allowable bending stresses, interferences, tubular
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.
Current edition approved Feb. 1, 2017July 1, 2021. Published February 2017July 2021. Originally approved in 2013. Last previous edition approved in 20132017 as
C1773 – 13.C1773 – 17. DOI: 10.1520/C1773-17.10.1520/C1773-21.
*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
C1773 − 21
test specimen geometries, test specimen preparation, test procedures, data collection, calculation, reporting requirements, and
precision/bias in the following sections.
Section
Scope 1
Referenced Documents 2
Terminology 3
Summary of Test Method 4
Significance and Use 5
Interferences 6
Apparatus 7
Hazards 8
Test Specimens 9
Test Procedure 10
Calculation of Results 11
Report 12
Precision and Bias 13
Keywords 14
Annexes
Interferences Annex A1
Test Specimen Geometry Annex A2
Grip Fixtures and Load Train Couplers Annex A3
Allowable Bending and Load Train Alignment Annex A4
Test Modes and Rates Annex A5
1.7 Units—The values stated in SI units are to be regarded as standard.
1.8 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 8.
1.9 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.
2. Referenced Documents
2.1 ASTM Standards:
C1145 Terminology of Advanced Ceramics
C1239 Practice for Reporting Uniaxial Strength Data and Estimating Weibull Distribution Parameters for Advanced Ceramics
C1273 Test Method for Tensile Strength of Monolithic Advanced Ceramics at Ambient Temperatures
C1557 Test Method for Tensile Strength and Young’s Modulus of Fibers
D3878 Terminology for Composite Materials
D5450 Test Method for Transverse Tensile Properties of Hoop Wound Polymer Matrix Composite Cylinders
E4 Practices for Force Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E83 Practice for Verification and Classification of Extensometer Systems
E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or
Process
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E251 Test Methods for Performance Characteristics of Metallic Bonded Resistance Strain Gages
E337 Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E1012 Practice for Verification of Testing Frame and Specimen Alignment Under Tensile and Compressive Axial Force
Application
3. Terminology
3.1 Definitions:
3.1.1 Pertinent definitions, as listed in Terminology C1145, Practice E1012, Terminology D3878, and Terminology E6, are shown
in the following with the appropriate source in bold type. Additional terms used in conjunction with this test method are defined
in the following:
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
C1773 − 21
3.1.2 advanced ceramic, n—a highly engineered, high performance high-performance, predominantly nonmetallic, inorganic,
ceramic material having specific functional attributes. C1145
3.1.3 axial strain, n—the average of the longitudinal strains measured at the surface on opposite sides of the longitudinal axis of
symmetry of the test specimen by two strain-sensing devices located at the mid length of the reduced section. E1012
3.1.4 bending strain, n—the difference between the strain at the surface and the axial strain. In general, the bending strain varies
from point to point around and along the reduced section of the test specimen. E1012
3.1.5 ceramic matrix composite, n—a material consisting of two or more materials (insoluble in one another) in which the major,
continuous component (matrix component) is a ceramic, while the secondary component/s (reinforcing component) may be
ceramic, glass-ceramic, glass, metal, or organic in nature. These components are combined on a macroscale to form a useful
engineering material possessing certain properties or behavior not possessed by the individual constituents. C1145
3.1.6 continuous fiber-reinforced ceramic matrix composite (CFCC), n—a ceramic matrix composite in which the reinforcing
phase consists of a continuous fiber, continuous yarn, or a woven fabric. C1145
3.1.7 fracture (breaking) force, P , n—the force at which the test specimen ruptures, breaking into two or more pieces.
fracture
3.1.8 fracture strength, S , n—the tensile stress at which the test specimen ruptures, breaking into two or more pieces or where the
f
applied force drops off significantly. Typically, a 10 % force drop off is considered significant.
3.1.9 gage length, l , n—the original length of that portion of the test specimen over which strain or change of length is
O
determined. E6
3.1.10 matrix-cracking matrix cracking stress, n—the applied tensile stress at which the matrix in the composite cracks into a
series of roughly parallel blocks normal to the tensile stress.
3.1.10.1 Discussion—
In some cases, the matrix cracking stress may be indicated on the stress-strain curve by deviation from linearity (proportional limit)
or incremental drops in the stress with increasing strain. In other cases, especially with materials which do not possess a linear
portion of the stress-strain curve, the matrix cracking stress may be indicated as the first stress at which a permanent offset strain
is detected in the unloading stress-strain (elastic limit).
3.1.11 modulus of elasticity, E, n—the ratio of stress to corresponding strains below the proportional limit. E6
3.1.12 modulus of resilience, U , n—strain energy per unit volume required to elastically stress the material from zero to the
r
proportional limit indicating the ability of the material to absorb energy when deformed elastically and return it when unloaded.
3.1.13 modulus of toughness, U , n—strain energy per unit volume required to stress the material from zero to final fracture
t
indicating the ability of the material to absorb energy beyond the elastic range (that is, damage tolerance of the material).
3.1.13.1 Discussion—
The modulus of toughness can also be referred to as the cumulative damage energy and as such is regarded as an indication of
the ability of the material to sustain damage rather than as a material property. Fracture mechanics methods for the characterization
of CFCCs have not been developed. The determination of the modulus of toughness as provided in this test method for the
characterization of the cumulative damage process in CFCCs may become obsolete when fracture mechanics methods for CFCCs
become available.
3.1.14 proportional limit stress, σ , n—the greatest stress that a material is capable of sustaining without any deviation from
o
proportionality of stress to strain (Hooke’s law). E6
3.1.14.1 Discussion—
Many experiments have shown that values observed for the proportional limit vary greatly with the sensitivity and accuracy of the
testing equipment, eccentricity of loading, the scale to which the stress-strain diagram is plotted, and other factors. When
determination of proportional limit stress is required, the procedure and sensitivity of the test equipment should be specified.
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3.1.15 percent bending, n—the bending strain times 100 divided by the axial strain. E1012
3.1.16 slow crack growth, n—subcritical crack growth (extension) which may result from, but is not restricted to, such
mechanisms as environmentally-assisted environmentally assisted stress corrosion or diffusive crack growth. C1145
3.1.17 stress corrosion, n—environmentally induced degradation that results in the formation and growth of cracks and/or damage
in glasses and many ceramics when subjected to the combined action of a corroding agent and stress. C1145
3.1.17.1 Discussion—
Such environmental effects commonly include the action of moisture, as well as other corrosive species, often with strong
temperature dependence.
3.1.18 tensile strength, S , n—the maximum tensile stress which a material is capable of sustaining. Tensile strength is calculated
u
from the maximum force during a tension test carried to rupture and the original cross-sectional area of the test specimen. E6
3.1.19 tow, n—in fibrous composites, a continuous, ordered assembly of essentially parallel, collimated filaments, normally
without twist and of continuous filaments. D3878
3.1.20 uniaxial tension, n—the application of tensile force coaxially with the long dimension of the test specimen.
4. Summary of Test Method
4.1 This test method involves the testing of a ceramic composite tube/cylinder with a known wall thickness in monotonic uniaxial
tension at ambient temperature. The prepared test specimen with a defined gage section is fitted/bonded into a loading fixture and
the test specimen/fixture assembly is mounted in the testing machine. The test specimen is loaded in axial tension while recording
the applied force and resulting strain. The axial tensile strength S and the fracture strength S are determined from the maximum
u f
applied force and the fracture force. The axial strains, the proportional limit stress, and the tensile modulus of elasticity are
determined from the stress-strain response data.
4.2 Tensile strength as used in this test method refers to the tensile strength obtained under monotonic uniaxial loading. In uniaxial
loading, the force is applied coaxially with the long dimension of the tube test specimen. Monotonic refers to a continuous nonstop
test rate with no reversals from test initiation to final fracture.
4.3 This test method is applicable to a range of test cylinder specimen geometries and sizes, which are described and considered
in theSection 9test specimen section. . A single fixed test specimen geometry cannot be defined because there is a wide range of
composite cylinder configurations in use and development. The different described test specimen geometries are typically
applicable to tubes with outer diameters of 10 to 150 mm and wall thicknesses of 1 to 25 mm, where the ratio of the outer
diameter-to-wall thickness (d /t) is between 5 and 30.
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5. Significance and Use
5.1 This test method provides information on the uniaxial tensile properties and tensile stress-strain response of a ceramic
composite tube—tensile strength and strain, fracture strength and strain, proportional limit stress and strain, tensile elastic modulus,
etc. The information may be used for material development, material comparison, quality assurance, characterization, and design
data generation.
5.2 Continuous fiber-reinforced ceramic composites (CFCCs) are composed of continuous ceramic-fiber directional (1-D,
2-D,(1D, 2D, and 3-D)3D) reinforcements in a fine grain-sized fine-grain-sized (<50 μm) ceramic matrix with controlled porosity.
Often these composites have an engineered thin (0.1 to 10 μm) interface coating on the fibers to produce crack deflection and fiber
pull-out. These ceramic composites offer high temperature high-temperature stability, inherent damage tolerance, and high degrees
of wear and corrosion resistance. As such, these ceramic composites are particularly suited for aerospace and high temperature
high-temperature structural applications (1, 2).
5.3 CFCC components have a distinctive and synergistic combination of material properties, interface coatings, porosity control,
The boldface numbers in parentheses refer to the list of references at the end of this standard.
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composite architecture (1-D, 2-D,(1D, 2D, and 3-D),3D), and geometric shape that are generally inseparable. Prediction of the
mechanical performance of CFCC tubes (particularly with braid and 3-D3D weave architectures) cannot be made by applying
measured properties from flat CFCC plates to the design of tubes. Direct uniaxial tensile strength tests of CFCC tubes are needed
to provide reliable information on the mechanical behavior and strength of tube geometries.
5.4 CFCCs generally experience “graceful” fracture from a cumulative damage process, unlike monolithic advanced ceramics
which fracture catastrophically from a single dominant flaw. The tensile behavior and strength of a CFCC are dependent on its
inherent resistance to fracture, the presence of flaws, and any damage accumulation processes. These factors are affected by the
composite material composition and variability in material and testing—components, reinforcement architecture and volume
fraction, porosity content, matrix morphology, interface morphology, methods of material fabrication, test specimen preparation
and conditioning, and surface condition.
5.5 The results of tensile tests of test specimens fabricated to standardized dimensions from a particular material or selected
portions of a part, or both, may not totally represent the strength and deformation properties of the entire, full-size end product
or its in-service behavior in different environments.
5.6 For quality control purposes, results derived from standardized tubular tensile test specimens may be considered indicative of
the response of the material from which they were taken, given primary processing conditions and post-processing heat treatments.
6. Interferences
6.1 Interferences in the testing of ceramic composite tubes arise from nine factors—material variability, dimensional variability
in the test specimen, test specimen size and volume effects, surface condition variability, fabrication effects, misalignment and
bending stresses, gripping and bonding failures, test environment variability, and out-of-gage failures. All of these factors have to
be understood and controlled for valid tests. These interference factors are discussed in detail in Annex A1.
7. Apparatus
7.1 Tensile Testing Machine, comprised of the following components and illustrated schematically in Fig. 1.
7.1.1 Fixed Member—A fixed or essentially stationary member to which one end of the tension specimen/fixture assembly can be
attached.
7.1.2 Movable Member—A movable member to which the opposite end of the tension specimen/fixture assembly can be attached.
7.1.3 Drive Mechanism, for imparting to the movable member a uniform controlled velocity with respect to the fixed member, this
velocity to be regulated as specified in 10.2.4 and Annex A5.
7.1.4 Force/Load Measurement—A suitable force measurement device capable of showing the total tensile force carried by the test
specimen. This device shall be essentially free of inertia-lag inertia lag at the specified rate of testing and shall indicate the applied
force with an accuracy of 61 % or better within the selected force range of the testing machine. The accuracy of the force
measurement device shall be verified in accordance with PracticePractices E4.
7.1.5 Construction Materials—The fixed member, movable member, drive mechanism, load-train, load train, and fixtures shall be
constructed of such materials and in such proportions that the total system compliance of the system contributed by these parts
is minimized.
7.2 Gripping Fixtures—Various types of gripping devices may be used to transmit the measured force applied by the testing
machine to the tubular test specimens. Because of the brittle nature of the matrices of CFCCs, gripping devices must have a
uniform, continuous contact with the entire gripped section of the tubular test specimen. (Line contact, point contacts, and
nonuniform pressure can produce Hertizan-type stresses leading to crack initiation and fracture of the test specimen in the gripped
section.) Gripping devices can be classed generally as those employing active grip fixtures and those employing passive grip
interfaces as discussed in the following section and in Annex A3.
7.2.1 Active Grip Fixtures—Active grip interfaces use the direct application of a normal gripping force (through mechanical,
hydraulic, or pneumatic action) to the grip section of the test specimen. These active grips commonly use split circular collets that
encircle the outer circumference of the tube and grip the tube through a lateral or wedging action. This gripping action transmits
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FIG. 1 Tensile Test Apparatus
the uniaxial force applied by the test machine by friction between the collet faces and the tubular test specimen. Examples,
descriptions, and design/use factors for active grips are discussed in A3.1.
7.2.2 Passive Grip Fixtures—Passive grip interfaces transmit the force applied by the test machine to the tubular test specimen
through a direct adhesive bond into the grips or by mechanical action between geometric features on the test specimen and the grip
fixture. Examples, descriptions, and design/use factors for passive grips are discussed in A3.3.
7.2.3 Load Train Couplers—Various types of devices (load train couplers) may be used to attach the active or passive grip
assemblies to the testing machine. The load train couplers in conjunction with the type of gripping device play major roles in the
alignment of the load train and minimizing any extraneous bending stresses imposed in the test specimen. Load train couplers can
be classified generally as fixed and nonfixed and are discussed in A3.6.
7.2.3.1 Fixed Load Train Couplers—Fixed couplers usually employ concentricity (x,y alignment) and angularity adjusters to
minimize load train misalignments. With fixed load train couplers, alignment verification must be performed as discussed in 7.2.4
and Annex A4.
7.2.3.2 Fixed load train couplers are preferred in monotonic testing of CFCCs because they maintain a uniform stress across the
composite when localized deformation occurs in the test specimen.
7.2.3.3 Nonfixed Load Train Couplers—Nonfixed couplers produce self-alignment of the load train during the movement of the
crosshead. Generally the coupling devices rely upon freely moving linkages to eliminate applied moments as the load train
components are loaded. Knife edges, universal joints, hydraulic couplers, or air bearings are examples of such devices. The
operation of the nonfixed couplers must be verified for allowable bending as discussed in 7.2.4 and Annex A4.
7.2.4 Allowable Bending and Load Train Alignment—Extraneous and excessive bending stresses from misalignment in uniaxial
tensile tests can cause or promote nonuniform stress distributions and premature failure. These bending stresses are minimized by
aligning the load train for concentricity and angularity. The tensile test load train shall be properly aligned and verified in all tests.
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7.2.4.1 This verification of the alignment and maximum percent bending shall be conducted at a minimum at the beginning and
end of each test series. Annex A4 provides additional details on bending issues and alignment methods for CFCCs, along with a
detailed procedure for verification of load train alignment, based on Practice E1012.
7.2.4.2 The recommended maximum allowable percent bending at the onset of the cumulative fracture process (for example,
matrix cracking stress) for composite test specimens in this test method is five percent (5 %).5 %.
7.3 Strain Measurement—Strain should be determined by means of either a suitable extensometer or bonded resistance strain
gages. If Poisson’s ratio is to be determined, the tubular test specimen must be instrumented to measure strain in both axial and
circumferential directions.
7.3.1 Extensometers—Extensometers used for tensile testing of CFCC tubular test specimens shall satisfy Practice E83, Class B-1
requirements. Extensometers are recommended to be used in place of strain gages for test specimens with gage lengths >25 mm
and shall be used for high-deformation tests beyond the strain range of strain gages. Extensometers shall be calibrated periodically
in accordance with Practice E83. For extensometers mechanically attached to the test specimen, the attachment should be such as
to cause no damage to the specimen surface. In addition, the weight of the extensometer should be supported,supported so as not
to introduce bending stresses in the test specimen greater than thatthose allowed in 7.2.4.2.
7.3.2 Strain Gages—Although extensometers are commonly used for CFCC strain measurement, strain can also be determined
with bonded resistance strain gages and suitable strain recording equipment. The strain gages, surface preparation, and bonding
agents should be chosen to provide adequate performance on the subject materials. Gage calibration certification shall comply with
Test Methods E251. A general reference on strain gages for composites is Tuttle and Brinson (3). Some guidelines on the use of
strain gages on ceramic composites are as follows.
7.3.2.1 Strain Gage Length—Unless it can be shown that strain gage readings are 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 length for the transverse direction. When testing woven fabric composites, the strain gages should have an active gage
length that is at least as great as the characteristic unit cell (repeating unit) of the weave; this averages the localized strain effects
of the fiber crossovers.
7.3.2.2 Surface Preparation—Many CFCCs have high degrees (>5 %) of porosity and surface roughness and therefore require
surface preparation (such as surface filling with epoxy) before the strain gages can be applied and fully bonded to the surface.
Reinforcing fibers in the composite should not be exposed or damaged during the surface preparation process.
7.3.2.3 Temperature Considerations—Consideration of some form of temperature compensation for the strain gages is
recommended, even when testing at standard laboratory atmosphere. Temperature compensation is required when testing in
nonambient temperature environments.
7.3.2.4 Transverse Sensitivity—Consideration should be given to the transverse sensitivity of the selected strain gage/s. This is
particularly important for a transversely mounted gage used to determine Poisson’s ratio, because composites often have markedly
different moduli in different directions in the fiber architecture. The strain gage manufacturer should be consulted for
recommendations on transverse sensitivity corrections and effects on composites.
7.3.2.5 Poisson’s ratio—Poisson’s ratio is easily determined with biaxial (0-90) (0° to 90°) strain gage rosettes which measure
the strain in both the axial and circumferential directions.
7.3.3 Data Acquisition—At the minimum, an autographic record of applied tensile force and gage section elongation (or strain)
versus time should be obtained. Either analog chart recorders or digital data acquisition systems can be used for this purpose,
although a digital record is recommended for ease of later data analysis.
7.3.3.1 Recording devices shall be accurate to within 60.1 % for the entire testing system including readout unit as specified in
Practices E4 and shall have a minimum data acquisition rate of 10 Hz, with a response of 50 Hz deemed more than sufficient.
7.3.3.2 Strain or elongation of the gage section, or both, should be recorded either similarly to the force or as independent variables
of force. Crosshead displacement of the test machine may also be recorded but should not be used to define displacement or strain
in the gage section, especially when self-aligning couplers are used in the load train.
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7.3.4 Dimension Measurement Devices—Ball or anvil type anvil-type micrometers should be used for measuring the test specimen
inner and outer diameters, to an accuracy of 0.02 mm or 1 % of the measured dimension, whichever is greater. Flat anvil type Flat,
anvil-type micrometer or calipers of similar resolution may be used for measuring the overall test specimen length and the defined
gage length.
7.3.5 Conditioning Chamber—When conditioning CFCC materials at non-ambient environments, an environmental conditioning
chamber with a controlled temperature and humidity levels is required. The chamber shall be capable of maintaining the required
temperature to within 63 °C and the required relative humidity level to within 65 %. Chamber conditions shall be monitored
either on an automated continuous basis or on a manual basis at regular intervals.
7.3.6 Environmental Test Chamber—When testing materials at other than ambient laboratory conditions (high/low humidity,
high/low temperatures, or both), the environmental chamber shall be capable of maintaining the gage section of the test specimen
at the required temperature to within 63 °C or the required relative humidity level to within 65 %, or both. Chamber conditions
shall be monitored during the test either on an automated continuous basis or on a manual basis at regular intervals.
7.3.7 Calibration and Standardization—The accuracy of all measuring equipment shall have certified calibrations that are current
at the time the equipment is used.
8. Hazards
8.1 During the conduct of this test method, the possibility of flying fragments of broken test material is high. The brittle nature
of advanced ceramics and the release of strain energy contribute to the potential release of uncontrolled fragments upon fracture.
Means for containment and retention of these fragments for later reconstruction and fractographic analysis is highly recommended.
(Plastic shields can be used to encircle the test fixture and to capture specimen fragments.)
8.2 Exposed fibers at the edges of CFCC test specimens present a hazard due to the sharpness and brittleness of the ceramic fiber.
All those required to handle these materials should be well informed of such conditions and the proper handling techniques.
9. Test Specimens
9.1 Geometry Considerations—CFCC tubes are fabricated in a wide range of sizes and geometries and across a wide spectrum
of different reinforcement fibers, distinctive ceramic matrix materials, and markedly different fabrication methods. In addition, the
fiber architecture for CFCC tubes has a broad range of configurations with different fiber loadings and directional variations. It is
currently not practical to define a single test specimen geometry that is applicable to all CFCC tubes.
9.2 The selection and definition of a tubular test specimen geometry depends on the purpose of the tensile testing effort. For
example, if the tensile strength of an as-fabricated component with a defined geometry is required, the dimensions of the resulting
tensile specimen may reflect the wall thickness, tube diameter, and length restrictions of the component. If it is desired to evaluate
the effects of interactions of various constituent materials for a particular CFCC manufactured via a particular processing route,
then the size of the test specimen and resulting gage section will reflect the size and geometry limits of that processing method.
In addition, grip devices and load train couplers (as discussed in Section 7 and Annex A3) will influence the final design of the
test specimen geometry.
9.3 Test Specimen Dimensions—This test method is generally applicable to tubes with outer diameters of 10 to 150 mm and wall
thicknesses of 1 to 25 mm, where the ratio of the outer diameter-to-wall thickness (d /t) is commonly between 5 and 30.
O
9.4 Test Specimen Geometries—Tubular test specimens are classified into two groups—straight-sided specimens and contoured
gage specimens, as shown in Figs. 2 and 3. Contour gage specimens are distinctive in having gage sections with thinner wall
thicknesses than the gripping sections. Both types of test specimens can be used in active and passive grips.
9.4.1 Annex A2 provides different examples of straight-sided and contoured gage test specimen tube geometries along with
geometry, design, fabrication, and preparation information. However, any CFCC tube geometry is acceptable if fracture failure
occurs consistently in the designated gage section with minimal extraneous bending stresses. Deviations from the example
geometries are permitted depending upon the particular CFCC tube being evaluated.
9.4.2 Although straight-sided tubular test specimens are easier to fabricate and are commonly used, tube test specimens with
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FIG. 2 Schematic of Straight-Sided Tube Specimen
FIG. 3 Schematic of Contoured Gage Section Tube Specimen
contoured gage sections are preferred to promote tensile failure in the uniformly stressed gage section. The contoured gage sections
are formed by integral thick-wall grip sections in the composites or by adhesively bonded collars/sleeves in the grip sections
(Annex A2). A key factor in contoured gage section specimens is the minimizing of any stress concentrations at the geometric
transitions into the gage sections.
9.5 Baseline Fabrication—The composition, architecture, and fabrication processing of the CFCC composite must be well defined
and suitably controlled to produce components and test specimens with acceptable, repeatable, and uniform physical and
mechanical properties. The composition, fiber architecture, fabrication processing, and lot identification should be fully determined
and documented.
9.6 Test Count and Test Specimen Sampling—A minimum of five valid test specimens is required for the purposes of estimating
a mean/average. A greater number of valid test specimens may be necessary if estimates regarding the form of the strength
distribution are required. The procedures outlined in Practice E122 should be used to estimate the number of tests needed for
determining a mean with a specified precision. If material cost or test specimen availability limits the number of possible tests,
fewer tests can be conducted to determine an indication of material properties. Test specimens should be selected and prepared
from representative CFCC samples that meet the stated testing objectives and requirements. The method of sampling shall be
reported.
9.7 Dimensional Tolerances and Variability—Dimensional tolerances will depend on the specific selected specimen geometry, the
method of manufacturing, and the performance requirements of the CFCC application. It is common for CFCC tubes to have
significant diametral variability (1 to 5 mm) in the as-fabricated condition, particularly for larger diameter tubes. The gage section
may or may not be machined to a specific tolerance (A2.7). Any significant (>2 %) dimensional variability in the OD and ID should
be determined and recorded.
9.8 Nondestructive evaluation (ultrasonics, thermal imaging, computerized tomography, etc.) may be used to assess internal
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morphology (delaminations, porosity concentrations, etc.) in the composite. Record these observations/measurements and the
results of any nondestructive evaluations and include them in the final report.
9.9 Surface Measurement—In some cases it is desirable, but not required, to measure surface roughness in the gage section to
quantify the surface condition. Methods such as contacting profilometry can be used to determine surface roughness parallel and
perpendicular to the tensile axis across a sufficient area to adequately characterize the surface. When measured, surface roughness
should be reported.
9.10 Test Specimen Storage and Handling—Care should be exercised in handling, packaging, and storage of finished test
specimens to avoid the introduction of random surface flaws. In addition, attention should be given to pre-test storage of test
specimens in controlled environments or desiccators to avoid unquantifiable environmental (for example, humidity) degradation
of test specimens prior to testing.
10. Test Procedure
10.1 Any deviation from this test method shall be described in detail in the test report.
10.2 Test Plan Parameters and Factors—The following test specimen parameters and experimental test factors have to be defined
in detail as part of the test plan.
10.2.1 The test specimen geometry, sampling method, test specimen preparation procedure, and any environmental conditioning
or test parameters (temperature, humidity, time), or combinations thereof.
10.2.2 The desired tensile properties and the data reporting format.
10.2.3 An estimate of the tensile properties for the CFCC being tested (tensile strength and strain, modulus of elasticity, etc.). This
information is used to determine the required capabilities and range of the test apparatus—load frame, load cells, grips,
extensometers, strain gages, etc.
10.2.4 Test modes and rates can have distinct and strong influences on fracture behavior of advanced ceramics, even at ambient
temperatures, depending on test environment or condition of the test specimen. Test modes may involve force, displacement, or
strain control. Recommended rates of testing are intended to be sufficiently rapid to obtain the maximum possible tensile strength
at fracture of the material. Typically, fracture should occur within 5 to 60 s after the start of the test. Annex A5 describes the
different test modes and provides guidance on how to choose a test mode and rate. In all cases, the test mode and rate must be
reported.
10.2.5 The method of strain measurement (extensometer, strain gauge, or both) and the strain measurement plan (type and gage
length of extensometer, type and number of strain gauges, locations/positions, and control/measurement system) should be noted
and reported.
10.3 Test Specimen Preparation—Test specimen preparation consists of three steps—conditioning, measurement, and strain gauge
installation (if used).
10.3.1 Conditioning—Condition the test specimens at the desired temperature, humidity, and time, per the test plan.
10.3.2 Test Specimen Measurement—Conduct 100 % inspection/measurements of all test specimens for surface condition (cracks,
surface flaws, surface porosity, etc.). Note that the frequency of valid gage section fractures and minimal bending in the gage
section are dependent on test specimen dimensions being within the desired tolerances.
10.3.2.1 Measure the outer diameter (d ), the internal diameter (d )), or the wall thickness (t), or both, of the gage section of each
O i
test specimen to within 0.02 mm or 1 % of the measured dimension, whichever is greater. Make three measurements around the
circumference on at least three different cross-sectional planes along the length of the gage section. Record and report the measured
dimensions and locations of the measurements for use in the calculation of the tensile stress. Use the average of the multiple
measurements in the stress calculations [d = d – 2t].
i o
10.3.2.2 To avoid damage in the gage section area it is recommended that these measurements be made either optically (for
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example, an optical comparator) or mechanically using a self-limiting (friction or ratchet mechanism) flat, anvil-type micrometer
with anvil diameter of at least 5 mm. In all cases the resolution of the instrument shall be as specified in 7.3.4.
10.3.2.3 Exercise caution to prevent damage to the test specimen gage section. Ball-tipped micrometers may be preferred when
measuring test specimens with rough or uneven nonwoven surfaces.
10.3.2.4 Alternatively, to avoid damage to the gage section (or in cases where it is not possible to infer or determine gage section
wall thickness), use the procedures described in 10.13 to make post-fracture measurements of the gage section dimensions. Note
that in some cases, the fracture process can severely fragment the gage section in the immediate vicinity of the fracture, thus
making post-fracture measurements of dimensions difficult. In these cases, it is advisable to do pretest measurements,pre-test
measurements per 10.3.2, to assureensure reliable measurements.
10.3.2.5 Measure and record the overall length of the test specimen and the length of the gage section, if it is defined.
10.3.2.6 If needed, measure the surface finish of the gage section of the test specimens using a suitable method (see 9.7).
10.3.3 Strain Gage Installation—Attach strain gages to the test specimen per the strain measurement test plan, ensuring that strain
gages are properly oriented and securely bonded to the test specimen per the manufacturer’s instructions. (Strain gage installation
can also be done after the test specimen is bonded into the grip fixtures.)
10.4 Test Specimen Assembly/Fixturing—Two test specimen factors have to be considered in specimen assembly/fixturing—the
use of end plugs and the method of adhesive bonding.
10.4.1 End Plugs—End plugs may be used in active gripping to prevent collapse in the grip sections. If end plugs (A3.2) are being
used in the test (for active gripping), insert and bond the two end plugs into the test specimen, using the designated adhesive and
alignment procedure. Ensure that the end plugs are centered in the test specimen and at the proper depth. Cure the adhesive per
the manufacturer’s specifications.
10.4.2 Adhesive Bonding into the Grip Fixtures—If adhesive bonding grip fixtures are being used (Annex A3), the test specimen
should be secured into the two end fixtures by filling the fixture cavities with the adhesive material (prepared per the manufacturer’s
instructions). Position the test specimen into the two grip fixtures and use an alignment fixture to ensure that the two end fixtures
and the test specimen are aligned concentrically. Cure the adhesive per the manufacturer’s specifications. After curing, measure
the free length/distance between the end fixtures at four points at 90° intervals around the specimen/fixture circumference.
Significant deviations (>2 %) in the measured length are an indication of test specimen or grip section misalignment.
10.5 Load Train Alignment and Bending Stress Assessment—If load train alignment is done with a “dummy” specimen,
adjust/verify the alignment of the load train, per the guidance in 7.2.4 and Annex A4.
10.6 Test Specimen Insertion—Each grip system and test specimen geometry (as described in Section 7, Annex A2 and Annex
A3Annex A2, and Annex A3) will require a unique procedure for mounting the test specimen in the load train. If special fixture
components are required for each test, these should be identified and noted in the test report.
10.6.1 Mount the test specimen/assembly into the grips and load train, ensuring that the test specimen is properly positioned and
aligned in the grips. Tighten the grips evenly and firmly to the degree necessary to prevent slippage of the test specimen during
the test but not to the point where the specimen would be crushed.
10.6.2 If strain gages are used to monitor bending, the strain gages should be zeroed with the test specimen attached at only one
end, so that it is hanging free. This will ensure that bending due to the grip closure is factored into the measured bending.
10.6.3 If load train alignment is done with the actual test specimen, adjust/verify the alignment of the load train, per the guidance
in 7.2.4 and Annex A4.
10.6.4 Mark the test specimen with an indelible marker as to top and bottom and front (side facing the operator) in relation to the
test machine. In the case of strain-gaged test specimens, orient the test specimen such that the “front” of the test specimen and a
unique strain gage coincide (for example, Strain Gage 1, designated SG1).
10.7 Extensometers and Strain Gages—Mount/connect the extensometer/s on the test specimen, if an extensometer is being used.
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Connect the lead wires of any strain gages to the conditioning equipment and allow the strain gages to equilibrate under power
for at least 30 min prior to conducting the verification tests. This will minimize drift during the test.
10.8 Test Environment—If an environmental test chamber is being used, condition the test specimen at the defined temperature and
humidity for the designated period of time. Record the environmental conditions and the “time to equilibrium” for each test.
10.9 Testing Machine Set Up—Setup—Activate and adjust the testing machine for initial cross-headcrosshead position,
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