SIST EN ISO 20323:2021

SLOVENSKI STANDARD
oSIST prEN ISO 20323:2021
01-maj-2021
Fina keramika (sodobna keramika, sodobna tehnična keramika) - Mehanske
lastnosti keramičnih kompozitov pri temperaturi okolice in pri zračnem tlaku -
Ugotavljanje nateznih lastnosti cevi (ISO 20323:2018)
Fine ceramics (advanced ceramics, advanced technical ceramics) - Mechanical
properties of ceramic composites at ambient temperature in air atmospheric pressure -
Determination of tensile properties of tubes (ISO 20323:2018)
Hochleistungskeramik - Mechanische Eigenschaften keramischer Verbundwerkstoffe bei
Umgebungstemperatur unter atmosphärischen Luftdruck - Bestimmung der
Zugeigenschaften von Röhren (ISO 20323:2018)
Céramiques techniques - Propriétés mécaniques des composites céramiques à
température ambiante et à pression atmosphérique - Détermination des propriétés en
traction de tubes (ISO 20323:2018)
Ta slovenski standard je istoveten z: prEN ISO 20323
ICS:
81.060.30 Sodobna keramika Advanced ceramics
oSIST prEN ISO 20323:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 20323:2021

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oSIST prEN ISO 20323:2021
INTERNATIONAL ISO
STANDARD 20323
First edition
2018-03
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Mechanical properties of ceramic
composites at ambient temperature
in air atmospheric pressure —
Determination of tensile properties
of tubes
Céramiques techniques — Propriétés mécaniques des composites
céramiques à température ambiante et à pression atmosphérique —
Détermination des propriétés en traction de tubes
Reference number
ISO 20323:2018(E)
©
ISO 2018

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oSIST prEN ISO 20323:2021
ISO 20323:2018(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Email: copyright@iso.org
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Published in Switzerland
ii © ISO 2018 – All rights reserved

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oSIST prEN ISO 20323:2021
ISO 20323:2018(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 4
5 Apparatus . 4
6 Tubular test specimens . 8
6.1 Specimen specifications . 8
6.1.1 General. 8
6.1.2 Dimension . 8
6.1.3 Geometry . 8
6.1.4 Tolerances and variability . . 9
6.2 Specimen preparation . 9
6.2.1 General. 9
6.2.2 As-fabricated .10
6.2.3 Application-matched machining .10
6.2.4 Customary practices .10
6.2.5 Standard procedure.10
6.3 End collars .10
6.4 Test count and test specimens sampling .12
7 Test procedure .12
7.1 General .12
7.2 Test mode and rates .12
7.3 Testing technique .13
7.3.1 Measurement of test specimen dimensions .13
7.3.2 Instrumentation of test specimen .13
7.3.3 Test specimen mounting .13
7.3.4 Setting-up of strain measurement means .13
7.3.5 Measurements .14
7.3.6 Post-test analyses .15
7.4 Test validity .15
8 Calculation of results .15
8.1 Test specimen origin .15
8.2 Engineering stress and strain.16
8.3 Tensile strength .17
8.4 Strain at maximum tensile force .17
8.5 Proportionality ratio or pseudo-elastic modulus, elastic modulus .18
8.5.1 Stress-strain curves with a linear region .18
8.5.2 Nonlinear stress-strain curves .19
8.6 Poisson’s ratio (optional) .19
8.7 Statistics .19
9 Test report .20
9.1 General .20
9.2 Testing information.20
9.3 Test specimen and material .20
9.4 Equipment and test parameters .21
9.5 Test results.21
Annex A (informative) Gripping devices and load train couplers .22
Annex B (informative) Test specimen geometries .27
Bibliography .28
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oSIST prEN ISO 20323:2021
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Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
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oSIST prEN ISO 20323:2021
INTERNATIONAL STANDARD ISO 20323:2018(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Mechanical properties of ceramic composites
at ambient temperature in air atmospheric pressure —
Determination of tensile properties of tubes
1 Scope
This document specifies the conditions for the determination of tensile properties of ceramic matrix
composite tubes with continuous fibre-reinforcement at ambient temperature in air atmospheric
pressure. This document is specific to the tubular geometries since fibre architecture and specimen
geometry factors are distinctly different in composite tubes than in flat specimens.
This document provides information on the uniaxial tensile properties and tensile stress-strain response
such as tensile strength and strain, tensile elastic modulus and Poisson’s ratio. The information may
be used for material development, control of manufacturing (quality insurance), material comparison,
characterization, reliability and design data generation for tubular components.
This document addresses, but is not restricted to, various suggested test piece fabrication methods.
It applies primarily to ceramic and/or glass matrix composite tubes with a continuous fibrous-
reinforcement: unidirectional (1D filament winding and tape lay-up), bi-directional (2D braid and
weave) and tri-directional (xD, with 2 < x < 3), loaded along the tube axis.
Values expressed in this document are in accordance with the International System of Units (SI).
NOTE In most cases, ceramic matrix composites to be used at high temperature in air are coated with an
antioxidation coating.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 20507, Fine ceramics (advanced ceramics, advanced technical ceramics) — Vocabulary
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
ISO 17161, Fine ceramics (advanced ceramics, advanced technical ceramics) — Ceramic composites —
Determination of the degree of misalignment in uniaxial mechanical tests
ISO 9513, Metallic materials — Calibration of extensometer systems used in uniaxial testing
ISO 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment: Micrometers for
external measurements — Design and metrological characteristics
ASTM E2208-02, Standard Guide for Evaluating Non-Contacting Optical Strain Measurement Systems
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20507 and the following apply.
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oSIST prEN ISO 20323:2021
ISO 20323:2018(E)

ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
calibrated length
l
part of the test specimen that has uniform and minimum external diameter
3.2
gauge length
L
0
initial distance between reference points on the test specimen in the calibrated length
3.3
initial cross-section area
S
0
area of the test specimen within the calibrated length
3.4
effective cross-section area
S
0,eff
total area corrected by a factor, to account for the presence of an anti-oxidative protection
3.5
external diameter
d
o
outer distance through the centre of a tube from one side to the other
3.6
internal diameter
d
i
inner distance through the centre of a tube from one side to the other
3.7
longitudinal deformation
A
increase in the gauge length between reference points under a tensile force
3.8
longitudinal deformation under maximum tensile force
A
m
increase in the gauge length between reference points under maximum tensile force
3.9
tensile strain
ε
zz
relative change in the gauge length defined as the ratio A/L
0
3.10
tensile strain under maximum force
ε
zz,m
relative change in the gauge length defined as the ratio A /L
m 0
3.11
circumferential strain
ε
θθ
relative change in circumferential direction in the gauge length
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3.12
tensile stress
σ
tensile force supported by the test specimen at any time in the test divided by the initial cross-section
area (S )
0
3.13
effective tensile stress
σ
eff
tensile force supported by the test specimen at any time in the test divided by the effective cross-
section area (S )
0,eff
3.14
maximum tensile force
F
m
highest recorded tensile force in a tensile test on the test specimen when tested to failure
3.15
tensile strength
σ
m
ratio of the maximum tensile force to the initial cross-section area (S )
0
3.16
effective tensile strength
σ
m,eff
ratio of the maximum tensile force to the effective cross-section area (S )
0,eff
3.17
proportionality ratio
pseudo-elastic modulus
E
P
slope of the initial linear section of the stress-strain curve
Note 1 to entry: Examination of the stress-strain curves for ceramic matrix composites allows definition of the
following cases:
a) Material with an initial linear domain in the stress-strain curve.
The proportionality ratio or pseudo-elastic modulus is termed the elastic modulus, E, in the single case where the
linearity starts near the origin.
b) Material with no-linear section in the stress-strain curve.
In this case only stress-strain couples can be fixed.
3.18
effective proportionality ratio
effective pseudo-elastic modulus
E
P,eff
slope of the linear section of the stress-strain curve, if any, when the effective tensile stress is used
3.19
Poisson’s ratio
ν
θz
negative ratio of circumferential to axial strain
3.20
coordinate system
system used to determine location in space
Note 1 to entry: Cylindrical coordinates are adopted in the present document.
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Note 2 to entry: The notations shown in Figure 1 apply for space representation.
Key
z axial
r radial
θ circumferential
Figure 1 — Cylindrical coordinate system used for the CMC tubes
4 Principle
A prepared tubular test specimen of specified dimensions is loaded in monotonic uniaxial tension up
to fracture. The test is performed at constant cross-head displacement, or constant strain (or constant
loading rate). Both the applied force and resulting longitudinal strain are measured and recorded
simultaneously. The uniaxial tensile strength and strain are determined from the maximum applied
force, while the various other tensile properties are determined from the stress-strain response data.
Generally, the test is carried out under conditions of ambient temperature and environment.
NOTE 1 In uniaxial loading, the force is applied parallel to the tube axis. Monotonic refers to a continuous
nonstop test rate with no reversals from test initiation to final fracture.
NOTE 2 The use of constant loading rate only gives a valid tensile curve when the behaviour is linear up to
failure.
5 Apparatus
5.1 Test machine.
The test machine shall be equipped with a system for measuring the force applied to the tubular test
specimen conforming to grade 1 or better in accordance with ISO 7500-1.
5.2 Test specimen gripping.
Various types of gripping device may be used to transmit the measured force applied by the testing
machine to the tubular test specimen. It shall prevent the tubular test specimen from slipping.
The brittle nature of the matrices of continuous fibre ceramic composites (CFCCs) requires a uniform
and continuous contact between the grip components and the gripped section of the tubular test
specimen in order to minimize crack initiation and fracture in this area.
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Gripping devices can be generally classified as those employing active grip interfaces and those
employing passive grip interfaces that include gripping system with adhesive bonding or through a
pin-loaded fixture. Examples, descriptions and designs for both the gripping types are discussed in
Annex A.
If an active grip interface system is used, the length of the grip section shall be long enough to develop
sufficient friction force to transmit the tensile forces to the tubular test specimen. As a general rule,
grip lengths are defined at least 1,5 times higher than the external diameter of the specimen. If the
tubular test specimen is pulling out of the grips, thus failing to increase the clamping pressure, longer
grip lengths might be needed.
To prevent crushing of the tubular test specimen by the lateral pressure and subsequent collapse of the
tube wall, it is advisable to insert an end plug into the interior of the grip section of the tube specimen
or to provide a suitable geometry for end collars (see 6.3).
5.3 Load train couplers.
Various types of devices may be used to fix the active or passive grip interface 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 extraneous bending imposed in the tubular test specimen; they can be
generally classified as fixed and non-fixed and are discussed in Annex A.
If each system type can be used, the load train configuration shall ensure that the load indicated by
the load cell and the load experienced by the tubular test specimen are the same. The alignment shall
be checked and documented in accordance with, for example, the procedure described in ISO 17161
adapted to the tubular geometry of specimen.
−4
The maximum relative bending shall not exceed 5 % at an average strain of 5,10 .
5.4 Strain measurement.
5.4.1 General
Strain should be locally measured in order to avoid having to take into account the compliance of the
machine. This may be by means of suitable extensometers, bonded resistance strain gauges or digital
image correlation (DIC). If Poisson’s ratio is to be determined, the tubular test specimen must be
instrumented to measure strain in both longitudinal and circumferential directions.
5.4.2 Extensometers
Extensometers used for tensile testing of CFCC tubular test specimens shall be capable of continuously
recording the longitudinal strain at test temperature. They shall be of class 1 in accordance with
ISO 9513.
Extensometers with the highest gauge length are recommended (minimum of 25 mm required) and
shall be centrally located in the mid region of the axial direction of the gauge section of the tubular test
specimen.
If mechanical extensometers are used, the selected attachment should cause no damage to the specimen
surface. In addition, the weight of the extensometers should be supported, so as not to introduce
bending stresses in the tubular test specimen greater than that allowed in 5.3.
Extensometers should preferably be of a type that is capable of measuring elongation on two places of
the tubular test specimen for averaging of strain and/or determination of in-situ relative bending. Care
should be taken to correct for changes in calibration of the extensometer that may occur as a result of
operating under conditions different from calibration.
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5.4.3 Strain gauges
5.4.3.1 General
Although extensometers are commonly used to measure strain in tensile test of CFCC tubes, strain can
also be determined with bonded resistance strain gauges and suitable strain recording equipment. The
strain gauges, the surface preparation and the bonding agents should be chosen to provide adequate
performance on the tested materials.
Some guidelines on the use of strain gauges on CFCC tubes are as follows.
5.4.3.2 Strain gauge selection
Unless it can be shown that strain gauge readings are not unduly influenced by localized strain
events such as fibre crossovers, strain gauges should be not less than 9 mm to 12 mm in length for the
longitudinal direction and not less than 6 mm in length for the circumferential direction.
When testing braided or woven fabric composites, the strain gauges should have an active gauge length
that is at least as great as the characteristic unit cell (repeating unit) of the reinforcement; this averages
the localized strain effects of the fibre crossovers.
In uniaxial loading, a single-grid gauge pattern would normally be used with the gauge axe aligned to
coincide with the longitudinal direction of the tubular test specimen.
NOTE Poisson’s ratio can be determined with biaxial two-element (0–90) strain gauge rosettes which
measure the strain in both the longitudinal and circumferential directions.
5.4.3.3 Surface preparation
The relatively rough surface of composites usually requires some preparation prior to strain gauge
bonding. The basic steps have to include solvent degreasing, abrading or filling and cleaning.
Matrix-rich surfaces can usually be abraded with 320-grit silicon carbide paper (SCP-2) to produce
a satisfactory matte finish. However, unless their surfaces have been machined or have received a
smoothing treatment, tubular test specimens of poor matrix content composites or those with textured
surface require alternative techniques.
NOTE A typical method is to apply a thin epoxy precoat to smooth the surface irregularities and finish by
polishing.
Reinforcing fibres should not be exposed or damaged during the surface preparation process. In
particular, abrasion should be kept to a minimum to avoid possible damage to fibres in the external
surface of the composite.
5.4.4 Digital image correlation
5.4.4.1 General
The DIC method can also be used to determine local strain of CFCC tubular test specimens loaded in
tensile from the displacement field measurement. The general procedure to be followed for estimating
the strain shall be in accordance with ASTM E2208-02.
Some guidelines on the use of the DIC method on CFCC tubes are as follows.
5.4.4.2 Experimental setup
The experimental setup for DIC measurements requires a digital CCD camera coupled with an
optical macro lens to acquire high spatial resolution micrographs (a minimum of 20 µm per pixel is
recommended). In the present case, the use of a telecentric lens is required to overcome the curvature
effect of the tubular test specimens.
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The imaging conditions for DIC measurements have to be selected to ensure that the entire coupon
surface is in the best focal plane of the camera and that the highest possible magnification could be
attained. Annular illumination with white or monochromantic light is recommended to provide a
correct signal-to-noise ratio.
The camera needs to be able to acquire micrographs at a suitable frame rate in order to achieve a
sufficient
...