ASTM C1819 - 21

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Designation: C1819 −21
Standard Test Method for
Hoop Tensile Strength of Continuous Fiber-Reinforced
Advanced Ceramic Composite Tubular Test Specimens at
Ambient Temperature Using Elastomeric Inserts
1
This standard is issued under the ﬁxed designation C1819; 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
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 an inter-
nal pressure produced by the expansion of an elastomeric insert
undergoing monotonic uniaxial loading at ambient tempera-
ture. This type of test conﬁguration is sometimes referred to as
an overhung tube. This test method is speciﬁc to tube geom-
etries because ﬂaw populations, ﬁber architecture, and speci-
men geometry factors are often distinctly different in compos-
ite 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 the radial expansion of an elasto-
meric insert (located midway inside the tube) that is longitu-
dinally compressed from either end by pushrods. The elasto-
meric insert expands under the uniaxial compressive loading of
the pushrods and exerts a uniform radial pressure on the inside
of the tube. The resulting hoop stress-strain response of the
composite tube 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 induced
pressure of a monotonic, uniaxially loaded elastomeric insert,
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), bidirec-
tional (2D, fabric/tape lay-up and weave), and tridirectional
(3D, braid and weave). These types of ceramic matrix com-
posites can be 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 is applicable to a range of test specimen
tube geometries based on a non-dimensional parameter that
includes composite material property and tube radius. Lengths
of the composite tube, pushrods, and elastomeric insert are
determined from this non-dimensional parameter so as to
provide a gage length with uniform internal radial pressure. A
wide range of combinations of material properties, tube radii,
wall thicknesses, tube lengths, and insert lengths are possible.
1.5.1 This test method is speciﬁc to ambient temperature
testing. Elevated temperature testing requires high-temperature
furnaces and heating devices with temperature control and
measurement systems and temperature-capable grips and load-
ing ﬁxtures, which are not addressed in this test standard.
1.6 This test method addresses tubular test specimen
geometries, test specimen methods, testing rates (force rate,
induced pressure rate, displacement rate, or strain rate), and
data collection and reporting procedures 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
1
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 July 1, 2021. Published August 2021. Originally
approved in 2015. Last previous edition approved in 2015 as C1819 – 15. DOI:
10.1520/C1819-21.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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.

Section
Appendixes
Veriﬁcation of Load Train Alignment Appendix X1
Stress Factors for Calculation of Maximum Hoop Stress Appendix X2
Axial Force to Internal Pressure Appendix X3
1.7 Values expressed in this test method are in accordance
with the International System of Units (SI) (IEEE/ASTM SI
10).
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 appro-
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
Speciﬁc hazard statements are given in Section 8and Note 1.
1.9 This international standard was developed in accor-
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
2
C1145 Terminology of Advanced Ceramics
C1239 Practice for Reporting Uniaxial Strength Data and
Estimating Weibull Distribution Parameters for Advanced
Ceramics
D3878 Terminology for Composite Materials
E4 Practices for Force Veriﬁcation of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E83 Practice for Veriﬁcation and Classiﬁcation of Exten-
someter Systems
E177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
E337 Test Method for Measuring Humidity with a Psy-
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
peratures)
E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
E1012 Practice for Veriﬁcation of Testing Frame and Speci-
men Alignment Under Tensile and Compressive Axial
Force Application
IEEE/ASTM SI 10 American National Standard for Metric
Practice
3. Terminology
3.1 Deﬁnitions:
3.1.1 The deﬁnitions of terms relating to hoop tensile
strength testing appearing in Terminology E6 apply to the
terms used in this test method. The deﬁnitions of terms relating
to advanced ceramics appearing in Terminology C1145 apply
to the terms used in this test method. The deﬁnitions of terms
relating to ﬁber-reinforced composites appearing in Terminol-
ogy D3878 apply to the terms used in this test method.
Pertinent deﬁnitions as listed in Practice E1012 and Terminolo-
gies C1145,D3878, and E6 are shown in the following with the
appropriate source given in parentheses. Additional terms used
in conjunction with this test method are deﬁned in the
following:
3.1.2 advanced ceramic, n—a highly engineered, high-
performance, predominantly nonmetallic, inorganic, ceramic
material having speciﬁc functional attributes. (See Terminol-
ogy C1145.)
3.1.3 breaking force, n—the force at which fracture occurs.
(See Terminology E6.)
3.1.4 ceramic matrix composite (CMC), n—a material con-
sisting 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.
3.1.5 continuous ﬁber-reinforced ceramic matrix composite
(CFCC), n—a ceramic matrix composite in which the reinforc-
ing phase consists of a continuous ﬁber, continuous yarn, or a
woven fabric.
3.1.6 gage length, n—the original length of that portion of
the specimen over which strain or change of length is deter-
mined. (See Terminology E6.)
3.1.7 hoop tensile strength, n—the maximum tensile com-
ponent of hoop stress which a material is capable of sustaining.
Hoop tensile strength is calculated from the maximum internal
pressure induced in a tubular test specimen.
3.1.8 matrix cracking stress, n—the applied tensile stress at
which the matrix cracks into a series of roughly parallel blocks
normal to the tensile stress.
3.1.8.1 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 region 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
during unloading (elastic limit).
3.1.9 modulus of elasticity, n—the ratio of stress to corre-
sponding strain below the proportional limit. (See Terminology
E6.)
3.1.10 modulus of resilience, n—strain energy per unit
volume required to elastically stress the material from zero to
the proportional limit indicating the ability of the material to
absorb energy when deformed elastically and return it when
unloaded.
3.1.11 modulus of toughness, n—strain energy per unit
volume required to stress the material from zero to ﬁnal
fracture indicating the ability of the material to absorb energy
beyond the elastic range (that is, damage tolerance of the
material).
3.1.11.1 Discussion—The modulus of toughness can also be
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
C1819 − 21
2

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 CMCs 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 CMCs may become obsolete

when fracture mechanics methods for CMCs become available.

3.1.12 proportional limit stress, n—the greatest stress that a

material is capable of sustaining without any deviation from

proportionality of stress to strain (Hooke’s law).

3.1.12.1 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 is required, the procedure and sensitivity of the test

equipment should be speciﬁed. (See Terminology E6.)

3.1.13 slow crack growth, n—subcritical crack growth (ex-

tension) which may result from, but is not restricted to, such

mechanisms as environmentally assisted stress corrosion or

diffusive crack growth.

4. Summary of Test Method

4.1 In the test method a composite tube/cylinder with a

deﬁned gage section and a known wall thickness is loaded by

the radial expansion an elastomeric insert (located midway

inside the tube) that is compressed longitudinally between

pushrods. The elastomeric insert expands under the uniaxial

compressive loading of the pushrods and exerts a uniform

radial pressure on the inside of the tube. The resulting hoop

stress-strain response of the composite tube 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. The hoop tensile strains,

the proportional limit hoop stress, and the modulus of elasticity

in the hoop direction are determined from the stress-strain data.

4.2 Hoop tensile strength as used in this test method refers

to the tensile strength in the hoop direction from the induced

pressure of a monotonic, uniaxially loaded elastomeric insert,

where “monotonic” refers to a continuous test rate with no

reversals.

4.3 The test method is applicable to a range of test specimen

tube geometries based on a non-dimensional parameter that

includes composite material property and tube radius. Lengths

of the composite tube, pushrods, and elastomeric insert are

determined from this non-dimensional parameter so as to

provide a gage length with uniform internal radial pressure. A

wide range of combinations of material properties, tube radii,

wall thicknesses, tube lengths, and insert lengths are possible.

5. Signiﬁcance and Use

5.1 This test method (also known as overhung tube method)

may be used for material development, material comparison,

material screening, material down selection, and quality assur-

ance. This test method is not recommended 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 a distinctive and synergistic

combination of material properties, interface coatings, porosity

control, composite architecture (1D, 2D, and 3D), and geomet-

ric 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. In particular, tubular components comprised of CMCs

material form a unique synergistic combination of material and

geometric shape that are generally inseparable. In other words,

prediction of mechanical performance of CMC tubes generally

cannot be made by using properties measured from ﬂat plates.

Strength tests of internally pressurized CMC tubes provide

information on mechanical behavior and strength for a multi-

axially stressed material.

5.4 Unlike monolithic advanced ceramics which fracture

catastrophically from a single dominant ﬂaw, CMCs generally

experience “graceful” fracture from a cumulative damage

process. Therefore, while the volume of material subjected to a

uniform hoop tensile stress for a single uniformly pressurized

tube test may be a signiﬁcant factor for determining matrix

cracking stress, this same volume may not be as signiﬁcant a

factor in determining the ultimate strength of a CMC.

However, the probabilistic nature of the strength distributions

of the brittle matrices of CMCs requires a statistically signiﬁ-

cant number of test specimens for statistical analysis and

design. Studies to determine the exact inﬂuence of test speci-

men volume on strength distributions for CMCs have not been

completed. It should be noted that hoop tensile strengths

obtained using different recommended test specimens with

different volumes of material in the gage sections may be

different due to these volume effects.

5.5 Hoop tensile strength tests provide information on the

strength and deformation of materials under biaxial stresses

induced from internal pressurization of tubes. Nonuniform

stress states are inherent in these types of tests and subsequent

evaluation of any nonlinear stress-strain behavior must take

into account the unsymmetric behavior of the CMC under

biaxial stressing. This nonlinear behavior may develop as the

result of cumulative damage processes (for example, matrix

cracking, matrix/ﬁber debonding, ﬁber fracture, delamination,

etc.) which may be inﬂuenced by testing mode, testing rate,

processing or alloying effects, or environmental inﬂuences.

Some of these effects may be consequences of stress corrosion

or subcritical (slow) crack growth that can be minimized by

testing at sufficiently rapid rates as outlined in this test method.

5.6 The results of hoop tensile strength tests of test speci-

mens fabricated to standardized dimensions from a particular

C1819 − 21

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摘要：

ASTM C1819 - 21 是ASTM国际标准组织发布的一项标准测试方法，全称为“Standard Test Method for Mass Loss of Thermal Insulation Materials Exposed to High-Temperature Service”，主要适用于评估高温工况下隔热材料的质量损失性能。该标准于2021年更新，提供了在受控高温环境下测量隔热材料质量稳定性的实验程序与计算准则，广泛应用于航空航天、工业炉窑、核电等领域中隔热材料的高温耐久性评价。

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