ASTM C1863-18

Standard Test Method for Hoop Tensile Strength of Continuous Fiber-Reinforced Advanced Ceramic Composite Tubular Test Specimens at Ambient Temperature Using Direct Pressurization

SIGNIFICANCE AND USE
5.1 This test method (also known as “tube burst test”) may be used for material development, material comparison, material screening, material down selection, and quality assurance. This test method can also be used for material characterization, design data generation, material model verification/validation, or combinations thereof.  
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 (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.  
5.3 CFCC components have distinctive and synergistic combinations of material properties, interface coatings, porosity control, composite architecture (1D, 2D, and 3D), and geometric shapes that are generally inseparable. Prediction of the mechanical performance of CFCC tubes (particularly with braid and 3D weave architectures) may not be possible by applying measured properties from flat CFCC plates to the design of tubes. This is because fabrication/processing methods may be unique to tubes and not replicable to flat plates, thereby producing compositionally similar but structurally and morphologically different CFCC materials. In particular, tubular components comprised of CFCC material form a unique synergistic combination of material, geometric shape, and reinforcement architecture that are generally inseparable. In other words, prediction of mechanical performance of CFCC tubes generally cannot be made by using properties measured from flat plates. Strength tests of internally pressurized CFCC tubes provide information on mechanical behavior and strength for a multiaxially stressed material.  
5.4 Unlike monolithic advanced ceramics that fracture catastrophically from a single dominant flaw, CMCs generally experience “graceful” fracture from a cumulative damage process. The...
SCOPE
1.1 This test method covers the determination of the hoop tensile strength, including stress-strain response, of continuous fiber-reinforced advanced ceramic tubes subjected to direct internal pressurization that is applied monotonically at ambient temperature. This type of test configuration is sometimes referred to as “tube burst test.” This test method is specific to tube geometries, because flaw populations, fiber architecture, material fabrication, and test 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 loaded via internal pressurization from a pressurized fluid applied either directly to the material or through a secondary bladder inserted into the tube. The monotonically applied uniform radial pressure on the inside of the tube results in hoop stress-strain response of the composite tube that is recorded until failure of the tube. The hoop tensile strength and the hoop fracture strength are determined from the resulting maximum pressure and the pressure at fracture, respectively. The hoop tensile strains, the hoop proportional limit stress, and the modulus of elasticity in the hoop direction are determined from the stress-strain data. Note that hoop tensile strength as used in this test method refers to the tensile strength in the hoop direction from the introduction of a monotonically applied internal pressure where ‘monotonic’ refers to a continuous nonstop test rate without reversals from test initiation to final fracture.  
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 can be composed of a...

General Information

• Status: Published
• Publication Date: 31-Dec-2017
• ICS: 23.040.15 - Non-ferrous metal pipes
• ICS: 81.060.20 - Ceramic products
• Technical Committee: C28 - Advanced Ceramics
• Drafting Committee: C28.07 - Ceramic Matrix Composites

Relations

• 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 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 E4-14 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2014
• Refers: ASTM C1239-13 - Standard Practice for Reporting Uniaxial Strength Data and Estimating Weibull Distribution Parameters for Advanced Ceramics
• Effective Date: 01-Aug-2013
• Refers: ASTM D3878-07(2013) - Standard Terminology for Composite Materials
• Effective Date: 01-May-2013
• Refers: ASTM C1145-06(2013)e1 - Standard Terminology of Advanced Ceramics
• Effective Date: 01-Feb-2013
• Refers: ASTM C1145-06(2013) - Standard Terminology of Advanced Ceramics
• Effective Date: 01-Feb-2013
• Refers: ASTM E1012-12 - Standard Practice for Verification of Testing Frame and Specimen Alignment Under Tensile and Compressive Axial Force Application
• Effective Date: 01-Jun-2012
• Refers: ASTM E1012-12e1 - Standard Practice for Verification of Testing Frame and Specimen Alignment Under Tensile and Compressive Axial Force Application
• Effective Date: 01-Jun-2012
• Refers: ASTM E4-10 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2010

Overview

ASTM C1863-18 is an international standard developed by ASTM International for testing the hoop tensile strength of continuous fiber-reinforced advanced ceramic composite tubular test specimens at ambient temperature, using direct internal pressurization. Commonly referred to as the "tube burst test," this method provides a reliable means to assess the mechanical strength, stress-strain characteristics, and fracture behavior of advanced ceramic matrix composite (CMC) tubes under internal pressure. The test is essential for industries and research fields that rely on these high-performance materials for critical components.

Key Topics

• Hoop Tensile Strength: The standard outlines procedures for determining the maximum tensile stress in the circumferential (hoop) direction of tubular CMC specimens when subjected to gradually increasing internal pressure.
• Test Method Application: Designed specifically for composite tubes, this method accommodates unique aspects of composite tubular geometries, such as flaw populations, fiber architecture, and fabrication methods that are not directly comparable to flat plate specimens.
• Specimen Preparation: The protocol addresses a wide array of tube geometries, ensuring compatibility with various CMC types, such as unidirectional, bidirectional, and tridirectional fiber reinforcements.
• Stress-Strain Measurement: The procedure enables recording of hoop strain, proportional limit stress, modulus of elasticity, and fracture strength until tube failure, supporting comprehensive mechanical characterization.
• Safety and Quality Control: Emphasizes safe handling of brittle, high-strength materials and highlights the importance of consistent specimen preparation for quality assurance and material screening.

Applications

The ASTM C1863-18 standard is utilized for multiple purposes related to advanced ceramic composites:

• Material Development & Screening: The tube burst test supports development, comparison, and down selection of CMC materials by providing critical hoop tensile strength properties under realistic loading conditions.
• Quality Assurance: Manufacturers use this method for batch testing, ensuring that product performance meets specified requirements consistently.
• Design & Engineering Data: Engineers rely on this standardized test to obtain accurate design data for finite element modeling, safety assessments, and structure calculations, particularly where tubes are subject to internal pressures.
• Material Characterization: Researchers use the test to validate or verify material models and investigate the effects of composite architecture, interface coatings, porosity, and fabrication processes on tube mechanical performance.
• Performance Evaluation: The results inform end-users on the deformation and fracture behavior of CMC tubes, supporting confident application in aerospace, energy, chemical processing, and structural industries where catastrophic failure must be avoided.

Related Standards

Several standards complement or relate to ASTM C1863-18 for ceramic matrix composites assessment and terminology:

• ASTM C1145: Terminology of Advanced Ceramics
• ASTM C1239: Practice for Reporting Uniaxial Strength Data for Advanced Ceramics
• ASTM D3878: Terminology for Composite Materials
• ASTM E4: Practices for Force Verification of Testing Machines
• ASTM E6: Terminology Relating to Mechanical Testing Methods
• ASTM E83: Practice for Extensometer Verification
• ASTM E337: Methods for Measuring Humidity
• ASTM E1012: Practice for Verification of Testing Frame and Specimen Alignment
• IEEE/ASTM SI 10: Metric Practice Standard

Practical Value

Implementing ASTM C1863-18 ensures that evaluations of hoop tensile strength and stress-strain response in advanced ceramic composite tubes are consistent, reproducible, and accurate. This fosters reliable quality control, material innovation, and engineering design for high-performance and safety-critical applications. By aligning testing practices with international standards, organizations enhance material selection, elevate product confidence, and maintain compliance with global trade and regulatory requirements.

Keywords: ASTM C1863-18, hoop tensile strength, tube burst test, ceramic matrix composite, CMC tube, direct pressurization, advanced ceramics, stress-strain testing, material characterization, quality assurance.

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: C1863 − 18
Standard Test Method for
Hoop Tensile Strength of Continuous Fiber-Reinforced
Advanced Ceramic Composite Tubular Test Specimens at
Ambient Temperature Using Direct Pressurization
This standard is issued under the fixed designation C1863; 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 wide range of crystalline and amorphous ceramic matrix
compositions (oxide, carbide, nitride, carbon, graphite, and
1.1 This test method covers the determination of the hoop
other compositions).
tensile strength, including stress-strain response, of continuous
fiber-reinforced advanced ceramic tubes subjected to direct
1.4 Thistestmethoddoesnotdirectlyaddressdiscontinuous
internalpressurizationthatisappliedmonotonicallyatambient
fiber-reinforced, whisker-reinforced, or particulate-reinforced
temperature. This type of test configuration is sometimes
ceramics, although the test methods detailed here may be
referred to as “tube burst test.” This test method is specific to
equally applicable to these composites.
tube geometries, because flaw populations, fiber architecture,
1.5 Thetestmethodisapplicabletoarangeoftestspecimen
material fabrication, and test specimen geometry factors are
tubegeometriesbasedontheintendedapplicationthatincludes
often distinctly different in composite tubes, as compared to
composite material property and tube radius. Lengths of the
flat plates.
compositetube,lengthofthepressurizedsection,andlengthof
1.2 In the test method, a composite tube/cylinder with a
tube overhang are determined so as to provide a gage length
defined gage section and a known wall thickness is loaded via
with uniform internal radial pressure. A wide range of combi-
internal pressurization from a pressurized fluid applied either
nationsofmaterialproperties,tuberadii,wallthicknesses,tube
directlytothematerialorthroughasecondarybladderinserted
lengths, and lengths of pressurized section are possible.
into the tube. The monotonically applied uniform radial pres-
1.5.1 This test method is specific to ambient temperature
sure on the inside of the tube results in hoop stress-strain
testing.Elevatedtemperaturetestingrequireshigh-temperature
response of the composite tube that is recorded until failure of
furnaces and heating devices with temperature control and
the tube. The hoop tensile strength and the hoop fracture
measurement systems and temperature-capable pressurization
strength are determined from the resulting maximum pressure
methods which are not addressed in this test method.
and the pressure at fracture, respectively. The hoop tensile
strains, the hoop proportional limit stress, and the modulus of
1.6 This test method addresses tubular test specimen
elasticity in the hoop direction are determined from the
geometries, test specimen preparation methods, testing rates
stress-straindata.Notethathooptensilestrengthasusedinthis
(that is, induced pressure rate), and data collection and report-
test method refers to the tensile strength in the hoop direction
ing procedures in the following sections:
from the introduction of a monotonically applied internal
Scope Section 1
pressure where ‘monotonic’refers to a continuous nonstop test
Referenced Documents Section 2
Terminology Section 3
rate without reversals from test initiation to final fracture.
Summary of Test Method Section 4
Significance and Use Section 5
1.3 This test method applies primarily to advanced ceramic
Interferences Section 6
matrix composite tubes with continuous fiber reinforcement:
Apparatus Section 7
unidirectional (1D, filament wound and tape lay-up), bidirec-
Hazards Section 8
Test Specimens Section 9
tional (2D, fabric/tape lay-up and weave), and tridirectional
Test Procedure Section 10
(3D, braid and weave). These types of ceramic matrix com-
Calculation of Results Section 11
posites can be composed of a wide range of ceramic fibers
Report Section 12
Precision and Bias Section 13
(oxide, graphite, carbide, nitride, and other compositions) in a
Keywords Section 14
Appendix
References
This test method is under the jurisdiction of ASTM Committee C28 on
Advanced Ceramics and is the direct responsibility of Subcommittee C28.07 on
1.7 Values expressed in this test method are in accordance
Ceramic Matrix Composites.
withtheInternationalSystemofUnits(SI)andIEEE/ASTMSI
Current edition approved Jan. 1, 2018. Published January 2018. Originally
approved in 2018. DOI: 10.1520/C1863-18. 10.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1863 − 18
1.8 This standard does not purport to address all of the whichthemajor,continuouscomponent(matrixcomponent)is
safety concerns, if any, associated with its use. It is the a ceramic, while the secondary component/s (reinforcing
responsibility of the user of this standard to establish appro- component) may be ceramic, glass-ceramic, glass, metal, or
priate safety, health, and environmental practices and deter- organic in nature. These components are combined on a
mine the applicability of regulatory limitations prior to use. macroscale to form a useful engineering material possessing
Specific hazard statements are given in Section 8. certain properties or behavior not possessed by the individual
1.9 This international standard was developed in accor- constituents. C1145
dance with internationally recognized principles on standard-
3.2.4 continuous fiber-reinforced ceramic matrix composite
ization established in the Decision on Principles for the
(CFCC), n—aceramicmatrixcompositeinwhichthereinforc-
Development of International Standards, Guides and Recom-
ing phase consists of a continuous fiber, continuous yarn, or a
mendations issued by the World Trade Organization Technical
woven fabric. C1145
Barriers to Trade (TBT) Committee.
3.2.5 gage length (L), n—the original length of that portion
of the specimen over which strain or change of length is
2. Referenced Documents
determined. E6
2.1 ASTM Standards:
–2
3.2.6 hoop fracture strength (FL ), n—the tensile compo-
C1145Terminology of Advanced Ceramics
nent of hoop stress at the point when the structural integrity of
C1239Practice for Reporting Uniaxial Strength Data and
the material is compromised and the tubular test specimen
Estimating Weibull Distribution Parameters forAdvanced
ruptures. Hoop fracture strength is calculated from the internal
Ceramics
pressure induced at rupture of the tubular test specimen.
D3878Terminology for Composite Materials
–2
E4Practices for Force Verification of Testing Machines
3.2.7 hoop stress (FL ), n—the tensile stress in the circum-
E6Terminology Relating to Methods of MechanicalTesting
ferential direction of a tube or pipe due to internal hydrostatic
E83Practice for Verification and Classification of Exten-
pressure.
someter Systems
–2
3.2.8 hoop tensile strength (FL ), n—the maximum tensile
E337Test Method for Measuring Humidity with a Psy-
component of hoop stress which a material is capable of
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
sustaining. Hoop tensile strength is calculated from the maxi-
peratures)
mum internal pressure induced in a tubular test specimen.
E1012Practice for Verification of Testing Frame and Speci-
–2
3.2.9 matrix cracking stress (FL ), n—the applied tensile
men Alignment Under Tensile and Compressive Axial
stress at which the matrix cracks into a series of roughly
Force Application
parallel blocks normal to the tensile stress.
IEEE/ASTM SI 10American National Standard for Metric
3.2.9.1 Discussion—In some cases, the matrix cracking
Practice
stress may be indicated on the stress-strain curve by deviation
3. Terminology from linearity (proportional limit) or incremental drops in the
stress with increasing strain. In other cases, especially with
3.1 Thedefinitionsoftermsrelatingtohooptensilestrength
materials which do not possess a linear region of the stress-
testingappearinginTerminologyE6applytothetermsusedin
strain curve, the matrix cracking stress may be indicated as the
this test method. The definitions of terms relating to advanced
first stress at which a permanent offset strain is detected in the
ceramics appearing in Terminology C1145 apply to the terms
during unloading (elastic limit).
used in this test method. The definitions of terms relating to
–2
fiber-reinforced composites appearing in Terminology D3878 3.2.10 modulus of elasticity (FL ), n—the ratio of stress to
applytothetermsusedinthistestmethod.Pertinentdefinitions corresponding strain below the proportional limit. E6
–3
as listed in Practice E1012 and Terminologies C1145, D3878,
3.2.11 modulus of resilience (FLL ), n—strain energy per
and E6 are shown in the following with the appropriate source
unitvolumerequiredtoelasticallystressthematerialfromzero
given in parentheses. Additional terms used in conjunction
totheproportionallimitindicatingtheabilityofthematerialto
with this test method are defined in the following:
absorb energy when deformed elastically and return it when
3.2 Definitions: unloaded.
–3
3.2.1 advanced ceramic, n—a highly engineered, high-
3.2.12 modulus of toughness (FLL ), n—strain energy per
performance, predominantly nonmetallic, inorganic, ceramic
unit 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
3.2.2 breaking force (F), n—the force at which fracture
beyond the elastic range (that is, damage tolerance of the
occurs. E6 material).
3.2.12.1 Discussion—Themodulusoftoughnesscanalsobe
3.2.3 ceramic matrix composite (CMC), n—a material con-
referred to as the “cumulative damage energy” and as such is
sisting of two or more materials (insoluble in one another) in
regardedasanindicationoftheabilityofthematerialtosustain
damage rather than as a material property. Fracture mechanics
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
methods for the characterization of CMCs have not been
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
developed. The determination of the modulus of toughness as
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. provided in this test method for the characterization of the
C1863 − 18
cumulative damage process in CMCs may become obsolete iteshaveanengineeredthin(0.1to10µm)interfacecoatingon
whenfracturemechanicsmethodsforCMCsbecomeavailable. the fibers to produce crack deflection and fiber pull-out.
–2
3.2.13 proportionallimitstress(FL ),n—thegreateststress
5.3 CFCC components have distinctive and synergistic
that a material is capable of sustaining without any deviation
combinations of material properties, interface coatings, poros-
from proportionality of stress to strain (Hooke’s law).
ity control, composite architecture (1D, 2D, and 3D), and
3.2.13.1 Discussion—Many experiments have shown that
geometric shapes that are generally inseparable. Prediction of
valuesobservedfortheproportionallimitvarygreatlywiththe
the mechanical performance of CFCC tubes (particularly with
sensitivity and accuracy of the testing equipment, eccentricity
braid and 3D weave architectures) may not be possible by
of loading, the scale to which the stress-strain diagram is
applying measured properties from flat CFCC plates to the
plotted, and other factors. When determination of proportional
design of tubes. This is because fabrication/processing meth-
limit is required, the procedure and sensitivity of the test
ods may be unique to tubes and not replicable to flat plates,
equipment should be specified. E6
thereby producing compositionally similar but structurally and
3.2.14 slow crack growth, n—subcritical crack growth (ex-
morphologically different CFCC materials. In particular, tubu-
tension) which may result from, but is not restricted to, such
lar components comprised of CFCC material form a unique
mechanisms as environmentally assisted stress corrosion or
synergistic combination of material, geometric shape, and
diffusive crack growth. C1145
reinforcement architecture that are generally inseparable. In
other words, prediction of mechanical performance of CFCC
4. Summary of Test Method
tubes generally cannot be made by using properties measured
4.1 In this test method, a composite tube/cylinder with a
from flat plates. Strength tests of internally pressurized CFCC
defined gage section and a known wall thickness is loaded via
tubesprovideinformationonmechanicalbehaviorandstrength
internal pressurization from a pressurized fluid applied either
for a multiaxially stressed material.
directlytothematerialorthroughasecondarybladderinserted
into the tube. The monotonically applied uniform radial pres-
5.4 Unlikemonolithicadvancedceramicsthatfracturecata-
sure on the inside of the tube results in hoop stress-strain
strophically from a single dominant flaw, CMCs generally
response of the composite tube that is recorded until failure of
experience “graceful” fracture from a cumulative damage
the tube. The hoop tensile strength and the hoop fracture
process.Therefore,whilethevolumeofmaterialsubjectedtoa
strength are determined from the resulting maximum pressure
uniform hoop tensile stress for a single uniformly pressurized
and the pressure at fracture, respectively. The hoop tensile
tube test may be a significant factor for determining matrix
strains, the hoop proportional limit stress, and the modulus of
cracking stress, this same volume may not be as significant a
elasticity in the hoop direction are determined from the
factor in determining the ultimate strength of a CMC.
stress-strain data.
However, the probabilistic nature of the strength distributions
4.2 Hoop tensile strength as used in this test method refers of the brittle matrices of CMCs requires a statistically signifi-
to the tensile strength in the hoop direction from the introduc-
cant number of test specimens for statistical analysis and
tionofamonotonicallyappliedinternalpressurewhere‘mono-
design. Studies to determine the exact influence of test speci-
tonic’refers to a continuous nonstop test rate without reversals
men volume on strength distributions for CMCs have not been
from test initiation to final fracture.
completed. It should be noted that hoop tensile strengths
obtained using different recommended test specimens with
4.3 Thetestmethodisapplicabletoarangeoftestspecimen
tube geometries based on a nondimensional parameter that different volumes of material in the gage sections may be
includes composite material property and tube radius. Lengths different due to these volume effects.
of the composite tube and other test specimen parameters are
5.5 Hoop tensile strength tests provide information on the
determinedsoastoprovideagagelengthwithuniforminternal
strength and deformation of materials under stresses induced
radial pressure that results in only a hoop stress in the gage
from internal pressurization of tubes. Nonuniform stress states
section. A wide range of combinations of material properties,
may be inherent in these types of tests and subsequent
tube radii, wall thicknesses, tube lengths, pressurized lengths,
evaluation of any nonlinear stress-strain behavior must take
and overhang (that is, unpressurized) lengths are possible.
into account the asymmetric behavior of the CMC under
multiaxial stressing. This nonlinear behavior may develop as
5. Significance and Use
theresultofcumulativedamageprocesses(forexample,matrix
5.1 This test method (also known as “tube burst test”) may
cracking, matrix/fiber de-bonding, fiber fracture, delamination,
be used for material development, material comparison, mate-
etc.) which may be influenced by testing mode, testing rate,
rial screening, material down selection, and quality assurance.
processing or alloying effects, or environmental influences.
Thistestmethodcanalsobeusedformaterialcharacterization,
Some of these effects may be consequences of stress corrosion
design data generation, material model verification/validation,
or subcritical (slow) crack growth that can be minimized by
or combinations thereof.
testingatsufficientlyrapidratesasoutlinedinthistestmethod.
5.2 Continuous fiber-reinforced ceramic composites
(CFCCs)arecomposedofcontinuousceramic-fiberdirectional 5.6 The results of hoop tensile strength tests of test speci-
mens fabricated to standardized dimensions from a particular
(1D, 2D, and 3D) reinforcements in a fine grain-sized (50 µm)
ceramic matrix with controlled porosity. Often these compos- material or selected portions of a part, or both, may not totally
C1863 − 18
represent the strength and deformation properties of the entire fracturesoriginatingatsurfacesorneargeometricaltransitions.
full-size end product or its in-service behavior in different In addition, if deformations or strains are measured at surfaces
environments. where maximum or minimum stresses occur, bending may
introduce over- or under-measurement of strains depending on
5.7 For quality control purposes, results derived from stan-
the location of the strain measuring device on the specimen.
dardized tubular hoop tensile strength test specimens may be
Similarly, fracture from surface flaws may be accentuated or
considered indicative of the response of the material from
suppressed by the presence of the nonuniform stresses caused
which they were taken for, given primary processing condi-
by bending.
tions and post-processing heat treatments.
6.4 If an internal bladder is used to transfer the pressure to
5.8 The hoop tensile stress behavior and strength of a CMC
the tubular test specimen, friction between the insert and the
are dependent on its inherent resistance to fracture, the pres-
rough or unlubricated (or both) inner surface of test specimen
ence of flaws, or damage accumulation processes, or both.
canproduceaxialstressesontheinnerboreofthetubethatwill
Analysis of fracture surfaces and fractography, though beyond
affecthoopstressinthetubeifthewallthicknessofthebladder
the scope of this test method, is highly recommended.
is large. In addition, this friction can accentuate axial bending
stress.
6. Interferences
6.5 Fractures that initiate outside the gage section of a test
6.1 Test environment (vacuum, inert gas, ambient air, etc.),
specimenmaybeduetofactorssuchasstressconcentrationsor
including moisture content (for example, relative humidity),
geometrical transitions, extraneous stresses introduced by
may have an influence on the measured hoop tensile strength.
fixtures/load apparatuses, or strength-limiting features in the
In particular, the behavior of materials susceptible to slow
microstructureofthespecimen.Becausesuchnon-gagesection
crack growth fracture will be strongly influenced by test
fractures will usually constitute invalid tests, provide an
environment and testing rate. Conduct testing to evaluate the
explanation when differentiating between valid and invalid
maximumstrengthpotentialofamaterialininertenvironments
tests.
or at sufficiently rapid testing rates, or both, so as to minimize
slow crack growth effects. Conversely, testing can be con-
7. Apparatus
ducted in environments and testing modes and rates represen-
7.1 Various methods can be used to produce direct pressure
tative of service conditions to evaluate material performance
in the CMC tube. An overview of some of these methods is
under use conditions. When testing is conducted in uncon-
provided in Appendix X1. Specifics regarding test apparatus
trolled ambient air with the intent of evaluating maximum
are provided in the following sections.
strength potential, monitor and report relative humidity and
temperature. Test at humidity levels >65 % relative humidity 7.2 Testing Machines—Various methods can be used to
(RH). Report any deviations from this recommendation.
producepressureinthetube.Ifuniaxialtestmachinesareused
to apply uniaxial force to a chamber to produce internal
6.2 Surface preparation of test specimens, although nor-
pressurization to the tubular test specimen, then this machine
mally not considered a major concern in CMCs, can introduce
shall conform to the requirements of Practices E4. The axial
fabrication flaws that may have pronounced effects on hoop
forceusedininducingtheinternalpressureshallbeaccurateto
tensilestressmechanicalpropertiesandbehavior(forexample,
within 61%atanyforcewithintheselectedforcerangeofthe
shapeandleveloftheresultingstress-straincurve,hooptensile
testing machine as defined in Practices E4. A schematic
strength and strain, proportional limit stress and strain, etc.).
showing pertinent features of such a hoop tensile strength
Machining damage introduced during test specimen prepara-
testing apparatus is shown in Fig. 1 (1, 2).
tion can be either a random interfering factor in the determi-
nation of ultimate strength of pristine material (that is, in- 7.3 Fixtures:
creased frequency of surface-initiated fractures compared to
7.3.1 General—In general, two types of test setups and
volume-initiated fractures), or an inherent part of the strength related fixtures as detailed in the following subsections have
characteristics to be measured. Surface preparation can also
been used for hoop tensile strength testing of tubes: compres-
lead to the introduction of residual stresses. Universal or sion pressurization and direct pressurization.
standardizedtestmethodsofsurfacepreparationdonotexist.It 7.3.2 Compression Pressurization—Compression loading
should be understood that final machining steps may or may fixtures (1-4) used in combination with universal testing
not negate machining damage introduced during the initial machines to produce the internal pressure for the tubular test
machining.Thus,testspecimenfabricationhistorymayplayan specimens are generally composed of two parts: (1) hydraulic
important role in the measured strength distributions and piston assembly attached to the test machine, and (2) pressur-
should be reported. In addition, the nature of fabrication used ization test fixture in which the tubular test specimen is
forcertaincomposites(forexample,chemicalvaporinfiltration mounted and tested under pressure. A schematic drawing of
orhotpressing)mayrequirethetestingoftestspecimensinthe
such a setup is shown in Fig. 1.
as-processed condition (that is, it may not be possible to 7.3.3 Direct Pressurization—Direct pressurization of the
machine the test specimen faces).
tubular test specimen is obtained from an external source such
6.3 Internally pressurized tests of CMC tubes can produce
multiaxial stress distributions with maximum and minimum
The boldface numbers in parentheses refer to a list of references at the end of
stressesoccurringatthesurfaceofthetestspecimen,leadingto this standard.
C1863 − 18
FIG. 1 Schematic of an Internal Pressure Device Using a Universal Test Machine for Pressurization (2)
direction) tube with outer diameter of 100 mm and wall and tube wall
asahydraulicpumporpressurereservoir (5-12).Inletpressure
thickness of 2 mm. In this case:
to the tubular test specimen is controlled directly as shown in
Figs. 2 and 3.
2 2
4 4
3 1 2 v 3 1 2 0.15
~ ! ~ !
7.3.3.1 Studies (13) have shown that the pressurized length β 5 5 50.133
Œ Œ
tube 2 2 2 2
r t @100 2 2 2 #⁄2 2
~ ! ~ ~ ! !
i
of the tube, L, and hence minimum length of the tubular
1/mm such that L=9⁄β=9⁄0.133=67.38mm.
specimen or bladder (or both) can be calculated as:
7.4 Strain Measurement—Determine strain by means of
L$9⁄ β
suitable diametral or circumferential extensometers, strain
gages, or appropriate whole-field methods. If Poisson’s ratio is
and
to be determined, instrument the tubular test specimen to
3~1 2 v !
measure strain in both axial and circumferential directions.
β 5 (1)
Œ
tube 2 2
r t
~ !
i
7.4.1 Extensometry—Diametral or circumferential exten-
where: someters used for testing of CMC tubular test specimens shall
satisfy Practice E83, Class B-1 requirements, and are recom-
v = Poisson’s ratio of test material in the hoop direction,
tube
mended to be used in place of strain gages for test specimens
r = inner radius of tubular test specimen, mm, and
i
with gage lengths of ≥25 mm and shall be used for high-
t = wall thickness of tubular test specimen, mm.
NOTE 1—Example of a commercial CMC (v=0.15 in the hoop performancetestsbeyondtherangeofstraingageapplications.
FIG. 2 Schematic Diagram of Burst Tube Arrangement Showing Internal Bladder Length (Gage Length), lb, and Overhang Length of
Tube, σ (4)
C1863 − 18
NOTE 1—Caution is advised regarding imposing an axial compressive force.
FIG. 3 Schematic of Room Temperature Hydrostatic Test Facility (8)
Calibrate extensometers periodically in accordance with Prac- Note that many CMCs exhibit high degrees of porosity and
tice E83. For extensometers mechanically attached to the test surface roughness and therefore require surface preparation,
specimen,maketheattachmentsoastocausenodamagetothe
includingsurfacefilling,beforethestraingagescanbeapplied.
specimen surface. 7.4.3 Circumferential Displacement—In this method (8),a
7.4.2 Strain Gages—Alternatively, strain can also be deter-
“string” is wrapped around the circumference of the gage
mineddirectlyfromstraingages.Ideally,toeliminatetheeffect section of the tubular test specimen and is attached to spring-
of misaligned uniaxial strain gages, mount three-element
loaded linear variable differential transformers (LVDTs)
rosette strain gages on the test specimen to determine maxi- mounted on a rigid frame (see Fig. 4). The arrangement
mum principal strain which should be in the hoop direction.
monitors the circumferential change in displacement with
Unlessitcanbeshownthatstraingagereadingsarenotunduly
increasing pressure. The change in circumference, ∆C, can be
influenced by localized strain events such as fiber crossovers,
transformed into the outer diameter circumferential strain as
use strain gage lengths greater than three unit cells of the fiber
∆C/C where C is the original circumference.
o o
architecture but not less than 9 to 12 mm for the longitudinal
7.4.4 Whole-Field Strain Measurement—Digital image cor-
direction and greater than three unit cells of the fiber architec-
relation (DIC) is a whole-field, optical method that employs
ture or not less than 6 mm for the transverse direction. Note
trackingandimageregistrationtechniquesforaccurate2Dand
that larger strain gages may be required for fabric reinforce-
3D measurements of changes in images (14, 15).The resulting
ments to average the localized strain effects of the fiber
imageshowsthestraindistributionoverthesurfaceofthetube.
crossovers. However, larger strain gages adhered to the curved
NOTE 2—Several methods can be used to measure the whole-field
surfacesofthetubulartestspecimensmayhaveaninitialstrain
displacement distribution using DIC. Typically, an image is recorded
due to tube curvature that may render the strain reading
before deformation at a particular brightness distribution and then a
unusable. Choose strain gages, surface preparation, and bond-
similar brightness distribution is searched for in the image after deforma-
ing agents so as to provide adequate performance on the
tion. The displacement components of a pixel located at the center of the
subject materials. Employ suitable strain recording equipment. subset are determined, and the displacement distributions are obtained by
FIG. 4 LVDT/String Arrangements for Measuring Hoop (8)
C1863 − 18
repeating this procedure for corresponding pixels. To determine strain, a
warning. Pressure relief valves can minimize overpressure
localapproximation,usedinwhichaleast-squaresfitforfiveside-by-side
failures. Protective shielding can contain release of fluids or
data points, and each point strain is determined using partial differentia-
gases.
tion. In this case, the length of the five data points is equivalent to the
“gauge length” for the strain evaluation. The complete strain distribution
9. Test Specimens
can be obtained by repeating this procedure for the full field. For pressure
9.1 Test Specimen Geometry:
testing of tubular test specimens, DIC (14, 15) can employ a digital
camera with minimum of 1940×1480 pixels capability and a 12-bit 9.1.1 General—The geometry of tubular test specimens is
resolution equipped with a telecentric lens to measure displacement and
dependentontheultimateuseofthehooptensilestrengthdata.
strain field on the surface of the tubular test specimen. A photograph is
For example, if the hoop tensile strength of an as-fabricated
taken every second on an area of about 10 by 12 mm (or on the order of
component is required, the dimensions of the resulting test
one unit cell of the fiber architecture).Ahigh-contrast speckle pattern can
specimen may reflect the wall thickness, tube diameter, and
be obtained on the test specimen surface by applying a matte randomized
length restrictions of the component. If it is desired to evaluate
painting in order to produce an efficient image correlation.Aring-shaped
source with a monochromatic light can provide a homogeneous and
the effects of interactions of various constituent materials for a
uniform illumination to improve the signal-to-noise ratio.
particularCMCmanufacturedviaaparticularprocessingroute,
then the size of the test specimen and resulting gage section
7.5 DataAcquisition—Ataminimum,obtainanautographic
(that is, pressurized length) will reflect the desired volume to
record of applied pressure and gage section expansion or hoop
be sampled. In addition, pressurized length plus the any
strain versus time. Either analog chart recorders or digital data
overhang (unpressurized length) will influence the final design
acquisition systems can be used for this purpose, although a
of the test specimen geometry. Tubular test specimen geom-
digital record is recommended for ease of later data analysis.
etries to maximize or minimize stresses through the wall
Ideally, use an analog chart recorder or plotter in conjunction
thicknesshavebeenstudiedexperimentallyandanalytically (1,
with the digital data acquisition system to provide an immedi-
2, 13).
ate record of the test as a supplement to the digital record.
9.1.1.1 The following sections discuss the requirements of
Recording devices shall be accurate to within 60.1% for the
tubular test specimen geometries for measuring hoop tensile
entire testing system including readout unit as specified in
strength. Although any geometry is acceptable if it meets the
PracticesE4andshallhaveaminimumdataacquisitionrateof
requirements for test specimen dimensions and fracture
10 Hz, with a response of 50 Hz deemed more than sufficient.
location,deviationsfromtherecommendedgeometriesmaybe
7.5.1 Record strain or expansion of the gage section, or
necessarydependingupontheparticularCMCbeingevaluated.
both, either similarly to the pressure or as independent vari-
Conductstressanalysesofuntriedtestspecimenstoensurethat
ables of pressure.
stress concentrations leading to undesired fractures outside the
gage sections do not exist. Note that contoured specimens by
7.6 Dimension Measuring Devices—Micrometers and other
devicesusedformeasuringlineardimensionsshallbeaccurate their nature contain inherent stress concentrations due to
geometric transitions that add to hoop stress produced by
and precise to at least one-half the smallest unit to which the
internal pressurization. Stress analyses can indicate the mag-
individual dimension is required to be measured. For the
nitudeofsuchstressconcentrationswhilerevealingthesuccess
purposes of this test method, measure cross-sectional dimen-
of producing a near-uniform hoop tensile stress state in the
sions to within 0.02 mm, thereby requiring dimension measur-
gage section of the test specimen.
ing devices with accuracies of 0.01 mm.
9.1.2 Test Specimen Dimensions—Although the diameters
and wall thickness of CMC tubes can vary widely depending
8. Hazards
on the application, analytical and experimental studies have
8.1 Duringtheconductofthistestmethod,thepossibilityof
shown (13) that one can maximize the chances of obtaining
flying fragments of broken test material is high. The brittle
successful tests by using consistent ranges of overall tube
nature of advanced ceramics and the release of strain energy
length as follows:
contribute to the potential release of uncontrolled fragments
L $16 ⁄ β (2)
t
upon fracture. Provide means for containment and retention of
NOTE 3—Example of a commercial CMC (v=0.15 in the hoop
these fragments for later fractographic reconstruction/analysis
direction) tube with outer diameter of 100 mm and wall and tube wall
and to prevent respiration or injury.
thickness of 2 mm. In this case:
8.2 Exposed fibers at the edges of CMC test specimens 2 2
4 4
3 1 2 v 3 1 2 0.15
~ ! ~ !
β 5 5 50.133
Œ Œ
present a hazard due to the sharpness and brittleness of the tube 2 2 2 2
r t 100 2 2 2 ⁄2 2
~ ! ~@ ~ !# !
i
ceramic fiber. Inform all those required to handle these
1/mm such that L ≥16⁄β=119.8mm.
t
materials of such conditions and the proper handling tech-
9.1.3 Studies (3) have shown that successful tests are
niques.
achievable if the unpressurized length of the tube is such that
8.3 Pressurized fluids or gases when released in uncon- the overhang (that is, unpressurized length of the tube =
trolledways(forexample,duringfailureofacomponentofthe (L – L) ⁄2) is on the order of three unit cells or three wall
t
test system or fracture of the CMC tube) can occur without thickness, whichever is greater.
C1863 − 18
9.2 Test Specimen Preparation: 10. Test Procedure
9.2.1 Depending upon the intended application of the hoop
10.1 Test Specimen Dimensions—Determine the wall thick-
tensile strength data, use one of the following test specimen
ness and outer diameter of the gage section of each test
preparation procedures. Regardless of the preparation proce-
specimen to within 0.02mm. Make measurements on at least
dure used, report sufficient details regarding the procedure to
two diameters on at least three different cross-sectional planes,
allow replication.
foraminimumofsixmeasurementseachofouterdiameterand
9.2.2 As-Fabricated—The tubular test specimen should wall thickness. To avoid damage in the critical gage section
simulatethesurface/edgeconditionsandprocessingrouteofan
area, it is recommended that these measurements be made
application where no machining is used; for example, as-cast, either optically (for example, an optical comparator) or me-
sintered, or injection-molded part. No additional machining
chanicallyusingaself-limiting(frictionorratchetmechanism),
specifications are relevant. As-processed test specimens pos-
flat, anvil-type micrometer. When measuring dimensions be-
sessingroughsurfacetexturesandnonparalleledgesmaycause
tween the faces of woven materials using contacting
excessive misalignment or be prone to non-gage section
metrology, employ a self-limiting (friction or ratchet
fractures, or both.
mechanism), flat, anvil-type micrometer having anvil cross-
sectional dimensions of at least 5mm. In all cases, the
9.2.3 Application-Matched Machining—The tubular test
resolution of the instrument shall be as specified in 7.6.
specimen should have the same surface/edge preparation as
Exercise caution to prevent damage to the test specimen gage
that given to the component. Unless the process is proprietary,
report specifics about the stages of material removal, wheel section. Ball-tipped or sharp-anvil micrometers may be pre-
ferred when measuring small-diameter test specimens or ma-
grits, wheel bonding, amount of material removed per pass,
and type of coolant used. terials with rough or uneven nonwoven surfaces. Noncontact-
ingmetrologysuchasX-raycomputedtomographyatdifferent
9.2.4 Customary Practices—Ininstanceswhereacustomary
resolutions and magnifications, depending on the dimensional
machining procedure has been developed that is completely
tolerance, has been used to make dimensional measurements
satisfactory for a class of materials (that is, it induces no
on CMC tubes (16). Record and report the measured dimen-
unwanted surface/subsurface damage or residual stresses), use
sions and locations of the measurements for use in the
this procedure.
calculation of the hoop tensile stress. Use the average of the
9.2.5 Standard Procedure—In instances where 9.2.2 – 9.2.4
multiple measurements in the stress calculations.
are not appropriate, 9.2.5 shall apply. Studies to evaluate the
10.1.1 Alternatively,toavoiddamagetothegagesection(or
machinability of CMCs have not been completed. Therefore,
in cases where it is not possible to infer or determine gage
the standard procedure of 9.2.5 can be viewed as starting point
section wall thickness), use the procedures described in 9.1 to
guidelines and a more stringent procedure may be necessary.
make post-fracture measurements of the gage section dimen-
9.2.5.1 Conductallgrindingorcuttingwithamplesupplyof
sions.Notethatinsomecasesthefractureprocesscanseverely
appropriatefilteredcoolanttokeeptheworkpieceandgrinding
fragment the gage section in the immediate vicinity of the
wheel constantly flooded and particles flushed. Conduct grind-
fracture, thus making post-fracture measurements of dimen-
ing in at least two stages, ranging from coarse to fine rate of
sions difficult. In these cases, it is advisable to follow the
material removal. Conduct all cutting in one stage appropriate
procedures outlined in 9.1 for pre-test measurements to ensure
for the depth of cut.
reliable measurements.
9.2.5.2 Employ a stock removal rate on the order of
10.1.2 Conduct periodic, if not 100 %, inspection/
0.03mm per pass using diamond tools that have between 320
measurements of all test specimens and test specimen dimen-
and 600 grit. Remove equal stock where applicable.
sions to ensure compliance with the drawing specifications.
Generally, high-resolution optical methods (for example, an
NOTE 4—Exercise care in storing and handling of finished test speci-
mens to avoid the introduction of random and severe flaws. In addition, optical comparator) or high-resolution digital point contact
give attention to pre-test storage of test specimens in controlled environ-
methods (for example, coordinate measurement machine) are
mentsordesiccatorstoavoidunquantifiableenvironmentaldegradationof
satisfactory as long as the equipment meets the specifications
specimens prior to testing.
in 7.6. Note that the frequency of gage section fractures and
9.3 Number of Test Specimens—Test a minimum of five test bending in the gage section are dependent on proper overall
specimens in a valid manner for the purposes of estimating a
test specimen dimensions within the required tolerances.
mean. A greater number of test specimens tested validly may
10.1.3 In some cases it is desirable, but not required, to
be necessary if estimates regarding the form of the strength
measure surface finish to quantify the surface condition. Such
distribution are required. If material cost or test specimen
methodsascontactingprofilometryorX-raycomputedtomog-
availabilitylimitsthenumberofpossibletests,fewertestsmay
raphy (16) can be used to determine surface roughness parallel
beconductedtodetermineanindicationofmaterialproperties.
to the longitudinal axis. When quantified, surface roughness
should be reported.
9.4 ValidTest—Avalidindividualtestisonewhichmeetsall
the requirements of this test method with final fracture in the 10.2 Test Modes and Rates:
uniformly stressed gage section (that is, pressurized length) 10.2.1 General—Test modes and rates can have distinct and
unless those tests fracturing outside the gage section are strong influences on fracture behavior of advanced ceramics,
interpreted as interrupted tests for the purpose of censored test even at ambient temperatures, depending on test environment
analyses. or condition of the test specimen. Test modes may involve
C1863 − 18
force or pressure control. Recommended rates of testing are dF
˙
F 5 (4)
intended to be sufficiently rapid to obtain the maximum dT
possible hoop tensile strength at fracture of the material.
where:
However, rates other than those recommended here may be
˙
F = the required force rate, N/s,
usedtoevaluaterateeffects.Inallcases,thetestmodeandrate
F = the applied force, N, and
must be reported.
T = time, s.
10.2.1.1 Formonolithicadvancedceramicsexhibitinglinear
For the linear elastic region of CMCs, pressure rate is
elasticbehavior,fractureisattributedtoaweakest-linkfracture
calculated as:
mechanism generally attributed to stress-controlled fracture
from Griffith-like flaws. Therefore, a force-controlled test or
dp
p˙ 5 (5)
pressure-controlled with pressure generally related directly to dT
hoop tensile stress, is the preferred test mode. However, in
where:
CMCs the nonlinear stress-strain behavior characteristic of the
p˙ = the required pressure rate, (N/mm )/s,
“graceful” fracture process of these materials indicates a
p = the applied pressure, N/mm , and
cumulativedamageprocessthatisstraindependent.Generally,
T = time, s.
displacement or strain-controlled tests are employed in such
cumulative damage or yielding deformation processes to pre- 10.2.4 Ramp Segments—Normally, conduct tests in a single
vent a “runaway” condition (that is, rapid uncontrolled defor- ramp function at a single test rate from zero force to the
mationandfracture)characteristicofforce-orstress-controlled maximum force at fracture. However, in some instances
tests. Thus, to elucidate the potential “toughening” mecha- multiplerampsegmentsmightbeemployed.Inthesecases,use
aslowtestratetorampfromzeroforcetoanintermediateforce
nisms under controlled fracture of the CMC, displacement or
strain control is preferred. However, for sufficiently rapid test to allow time for removing “slack” from the test system.
rates, differences in the fracture process may not be noticeable Conduct the final ramp segment of the test from the interme-
diate pressure to the maximum pressure at fracture at the
and any of these test modes may be appropriate.
required (desired) test rate. Report the type and time duration
10.2.2 Strain Rate—Strain is the independent variable in
of the ramp.
nonlinear analyses such as yielding. As such, strain rate is a
method of controlling tests of deformation processes to avoid
10.3 Conducting the Hoop Tensile Strength Test:
“runaway” conditions. For the linear elastic region of CMCs,
10.3.1 Mounting the Test Specimen—Assemble the pressur-
strain rate can be related to strain measurement such that:
ized test fixture and tubular test specimen before testing can
dε
commence. Identify the components required for each test and
ε˙ 5 (3)
L
dT
note these in the test report. Mark the test specimen with an
indeliblemarkerastotopandbottomandfront(sidefacingthe
where:
operator) in relation to the test machine. In the case of
ε˙ = strain rate of the insert, (mm/mm)/s, and
L
strain-gaged test specimens, orient the test specimen such that
dε
⁄dT = slope of strain-time curve (mm/mm)/s.
the “front” of the test specimen and a unique strain gage (for
10.2.2.1 Note that strain-controlled tests can be accom- example, Strain Gage 1 designated ‘SG1’) coincide.
plished using a diametral or hoop extensometer contacting the
10.3.2 Preparations for Testing—Cleanandgreasetheblad-
gagesectionofthespecimenastheprimarycontroltransducer.
der(ifused)andboreofthetubulartestspecimen.Ifused,slide
–6 –1 –6 –1
Use strain rates on the order of 5 × 10 s to 50 × 10 s to
the bladder into the tube. Insert the tubular test specimen into
minimize environmental effects when testing in ambient air.
the pressurization test fixture and ready the test fixture for
Alternately, strain rates shall be selected to produce final
pressurization. Set the test mode and test rate on the test
fracture in 10 to 30s to minimize environmental effects when
machine. “Preload” the tubular test specimen with an initial
testing in ambient air.
pressuretoaddressanyclearancebetweenthebladderandtube
wall. The amount of “preload” will depend on the bladder
10.2.3 Force or Pressure
...