SIST EN ISO 14544:2025

SLOVENSKI STANDARD
01-marec-2025
Fina keramika (sodobna keramika, sodobna tehnična keramika) - Mehanske
lastnosti keramičnih kompozitov pri visoki temperaturi - Ugotavljanje lastnosti pri
stiskanju (ISO 14544:2025)
Fine ceramics (advanced ceramics, advanced technical ceramics) - Mechanical
properties of ceramic composites at high temperature - Determination of compressive
properties (ISO 14544:2025)
Hochleistungskeramik - Mechanische Eigenschaften von keramischen
Verbundwerkstoffen bei hoher Temperatur - Bestimmung der Eigenschaften unter Druck
(ISO 14544:2025)
Céramiques techniques - Propriétés mécaniques des composites à matrice céramique à
haute température - Détermination des caractéristiques en compression (ISO
14544:2025)
Ta slovenski standard je istoveten z: EN ISO 14544:2025
ICS:
81.060.30 Sodobna keramika Advanced ceramics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 14544
EUROPEAN STANDARD
NORME EUROPÉENNE
January 2025
EUROPÄISCHE NORM
ICS 81.060.30 Supersedes EN ISO 14544:2016
English Version
Fine ceramics (advanced ceramics, advanced technical
ceramics) - Mechanical properties of ceramic composites
at high temperature - Determination of compressive
properties (ISO 14544:2025)
Céramiques techniques - Propriétés mécaniques des Hochleistungskeramik-Mechanische Eigenschaften von
composites à matrice céramique à haute température - keramischen Verbundwerkstoffen bei hoher
Détermination des caractéristiques en compression Temperatur-Bestimmung der Eigenschaften unter
(ISO 14544:2025) Druck (ISO 14544:2025)
This European Standard was approved by CEN on 18 January 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14544:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 14544:2025) has been prepared by Technical Committee ISO/TC 206 "Fine
ceramics" in collaboration with Technical Committee CEN/TC 184 “Advanced technical ceramics” the
secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by July 2025, and conflicting national standards shall be
withdrawn at the latest by July 2025.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 14544:2016.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 14544:2025 has been approved by CEN as EN ISO 14544:2025 without any modification.

International
Standard
ISO 14544
Second edition
Fine ceramics (advanced ceramics,
2025-01
advanced technical ceramics) —
Mechanical properties of ceramic
composites at high temperature
— Determination of compressive
properties
Céramiques techniques — Propriétés mécaniques des composites
à matrice céramique à haute température — Détermination des
caractéristiques en compression
Reference number
ISO 14544:2025(en) © ISO 2025
ISO 14544:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 14544:2025(en)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Apparatus . 4
5.1 Test machine .4
5.2 Load train .4
5.3 Gastight test chamber .4
5.4 Set-up for heating .5
5.5 Strain measurement .5
5.5.1 General .5
5.5.2 Strain gauges.5
5.5.3 Extensometer .5
5.6 Temperature measurement devices .6
5.7 Data recording system .6
5.8 Dimension measuring devices .7
6 Test specimens . 7
6.1 General .7
6.2 Compression between platens . .7
6.3 Test specimen used with grips .9
7 Test specimen preparation .11
7.1 Machining and preparation .11
7.2 Number of test specimens . 12
8 Test procedures .12
8.1 Test set-up: temperature considerations . 12
8.1.1 General . 12
8.1.2 Controlled-temperature zone . 12
8.1.3 Temperature calibration . 12
8.2 Test set-up: other considerations . 13
8.2.1 Displacement rate . 13
8.2.2 Measurement of test-specimen dimensions. 13
8.2.3 Buckling . . 13
8.3 Testing technique .14
8.3.1 Specimen mounting .14
8.3.2 Setting of extensometer .14
8.3.3 Setting of inert atmosphere .14
8.3.4 Heating of test specimen .14
8.3.5 Measurements . 15
8.4 Test validity . 15
9 Calculation of results .15
9.1 Test specimen origin . 15
9.2 Compressive strength . 15
9.3 Strain at maximum compressive force .16
9.4 Compressive modulus .16
9.4.1 Calculation of compressive modulus .16
9.4.2 Calculation of compressive modulus with linear behaviour at the origin .17
9.4.3 Calculation of compressive modulus with non-linear behaviour .17
10 Test report . 17
11 Uncertainties .18

iii
ISO 14544:2025(en)
Annex A (informative) Illustration of compressive modulus. 19
Annex B (informative) Calibration method of the test temperature using a cartographic
specimen equipped with thermocouples .22
Bibliography .27

iv
ISO 14544:2025(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics, in collaboration with
the European Committee for Standardization (CEN) Technical Committee CEN/TC 184, Advanced technical
ceramics, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna
Agreement).
This second edition cancels and replaces the first edition (ISO 14544:2013), which has been technically
revised.
The main changes are as follows:
— alignment of the terms and definition with the vocabulary standard ISO 20507;
— addition of illustration of compressive modulus in Annex A;
— addition of a calibration method of the test temperature by using a cartographic specimen equipped with
thermocouples in Annex B.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
International Standard ISO 14544:2025(en)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Mechanical properties of ceramic composites
at high temperature — Determination of compressive
properties
1 Scope
This document specifies procedures for determination of the compressive behaviour of ceramic matrix
composite materials with continuous fibre reinforcement at elevated temperature in air, vacuum and
inert gas atmospheres. This document applies to all ceramic matrix composites with a continuous fibre
reinforcement, uni-directional (1D), bidirectional (2D) and multi-directional (xD, with x > 2), tested along
one principal axis of reinforcement or off axis conditions for 2D and xD materials. This document also applies
to carbon-fibre-reinforced carbon matrix composites (also known as carbon/carbon or C/C). Two cases of
testing are distinguished: compression between platens and compression using grips.
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 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment — Design and
metrological characteristics of micrometers for external measurements
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 9513, Metallic materials — Calibration of extensometer systems used in uniaxial testing
ISO 19634, Fine ceramics (advanced ceramics, advanced technical ceramics) — Ceramic composites — Notations
and symbols
ISO 20507, Fine ceramics (advanced ceramics, advanced technical ceramics) — Vocabulary
IEC 60584-1, Thermocouples — Part 1: EMF specifications and tolerances
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20507 and ISO 19634 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
test temperature
T
temperature of the test piece at the centre of the gauge length

ISO 14544:2025(en)
3.2
calibrated length
l
part of the test specimen that has uniform and minimum cross-section area
[SOURCE: ISO 20504:2022, 3.1]
3.3
gauge length
L
initial distance between reference points on the test specimen in the calibrated length
[SOURCE: ISO 20504:2022, 3.2, modified — term and definition, words before initiation of the test deleted.]
3.4
controlled-temperature zone
part of the calibrated length, including the gauge length, where the temperature is within a range of 50 °C of
the test temperature
3.5
initial cross-section area
S
o
cross-section area of the test specimen within the calibrated length, at room temperature before testing
3.5.1
apparent cross-section area
S
o app
area of the cross section
3.5.2
effective cross-section area
S
o eff
area corrected by a factor, to account for the presence of a coating
3.6
longitudinal deformation
A
decrease in the gauge length under a compressive force in the load direction
Note 1 to entry: The longitudinal deformation corresponding to the maximum compressive force is denoted as A .
c,m
3.7
compressive strain
ε
ratio of deformation to initial gauge length defined as the ratio A/L
Note 1 to entry: The compressive strain corresponding to the maximum compressive force is denoted as ε .
c,m
3.8
compressive force
F
c
uniaxial force carried by the test specimen at any time during the compression test
[SOURCE: ISO 20504:2022, 3.6, modified — word "compression" added.]
3.9
compressive stress
σ
compressive force (3.8) supported by the test specimen at any time in the test divided by the initial cross-
sectional area (3.5) such that σ = F /S
c o
[SOURCE: ISO 20504:2022, 3.8]
ISO 14544:2025(en)
3.9.1
apparent compressive stress
σ
app
ratio of the compressive force (3.8) supported by the test piece to the apparent cross-section area (3.5.1)
3.9.2
effective compressive stress
σ
eff
ratio of the compressive force (3.8) carried by the test piece to the effective cross-section area (3.5.2)
3.10
maximum compressive force
F
c,m
highest force recorded or force at failure during a compressive test
3.11
compressive strength
σ
c,m
greatest compressive stress (3.9) applied to a test specimen when tested to failure
[SOURCE: ISO 20504:2022, 3.9]
3.11.1
apparent compressive strength
σ
c,m app
ratio of the maximum compressive force (3.10) to the apparent cross-section area (3.5.1)
3.11.2
effective compressive strength
σ
c,m eff
ratio of the maximum compressive force (3.10) to the effective cross-section area (3.5.2)
3.12
compressive modulus
E
slope of the linear section of the stress-strain curve at or near the origin
Note 1 to entry: It is possible that a linear part does not exist or does not start at the origin. The different situations are
then described in the Annex A.
3.12.1
apparent compressive modulus
E
app
slope of the linear part of the stress-strain curve at or near the origin when the apparent compressive stress
(3.9.1) is used
3.12.2
effective compressive modulus
E
eff
slope of the linear part of the stress-strain curve at or near the origin, when the effective compressive stress
(3.9.2) is used
4 Principle
A test specimen of specified dimensions is heated to the test temperature, and loaded in compression. The
test is performed at constant crosshead displacement rate or constant deformation rate (or constant loading
rate). Force and longitudinal deformation are measured and recorded simultaneously.
NOTE The test duration is limited to reduce creep effects.

ISO 14544:2025(en)
When constant loading rate is used in the nonlinear region of the compressive curve, only the compressive
strength can be obtained from the test. In this region, constant crosshead displacement rate or constant
deformation rate is recommended to obtain the complete curve.
5 Apparatus
5.1 Test machine
The machine shall be equipped with a system for measuring the force applied to the test specimen that
shall conform to grade 1 or better in accordance with ISO 7500-1. This should prevail during actual test
conditions of, e.g. gas pressure and temperature.
5.2 Load train
The load train configuration shall ensure that the load indicated by the load cell and the load experienced by
the test specimen are the same.
The load train performance including the alignment system and the force transmitting system shall not
change because of heating.
The load train shall align the specimen axis with the direction of load application without introducing
bending or torsion in the specimen. The misalignment of the specimen shall be verified at room temperature
and documented. Several standards address this topic but it is recommended to comply with the procedure
-6
described in ISO 17161. The percent bending strain shall not exceed 5 % at an average strain of 500 x 10 .
There are two alternative means of load application:
a) Compression platens are connected to the load cell and on the moving crosshead. The platens should
have a larger diameter than the specimen base. The parallelism of these platens should be better than
0,01 mm, in the loading area, at room temperature and they shall be perpendicular to the load direction.
The use of platens is not recommended for compression testing of 1D and 2D materials with low
thickness due to buckling. For high temperature tests set-up, the platens parallelism value specified
in ISO 20504 is sometimes difficult to be determined by dimensional controls but remains a suitable
recommendation.
A compliant interlayer material between the test specimen and platens can be used for testing
macroscopically inhomogeneous materials to ensure even contact pressure. This material should be
chemically compatible with both test specimen and platen materials.
b) Grips are used to clamp and load the test specimen.
The grip design shall prevent the test specimen from slipping. The grips shall align the test specimen
axis with that of the applied force.
Conformity to this requirement should be verified and documented according to, for example, the procedure
described in Reference [1].
The grips or the platens may either be in the hot zone of the furnace or outside the furnace.
NOTE When grips or platens are outside the furnace, a temperature gradient exists between the centre of the
specimen, which is at the prescribed temperature, and the ends that are at the same temperature as the grips or
platens.
5.3 Gastight test chamber
The gastight chamber shall allow proper control of the test specimen environment in the vicinity of the test
specimen during the test. The installation shall be such that the variation of load due to the variation of
pressure is less than 1 % of the scale of the load cell being used.

ISO 14544:2025(en)
Where a gas atmosphere is used, the gas atmosphere shall be chosen depending on the material to be tested
and on test temperature. The level of pressure shall be chosen depending: on the material to be tested, on
temperature, on the type of gas, and on the type of extensometer.
Where a vacuum chamber is used, the level of vacuum shall not induce chemical and/or physical instabilities
of the test specimen material, and of extensometer rods, when applicable. Primary vacuum (typically 1 Pa
pressure) is recommended.
5.4 Set-up for heating
The set-up for heating shall be constructed in such a way that:
— the test coupon maximal temperature will never exceed the desired test temperature by more than 5 °C;
— the gauge length is actually included in the controlled temperature zone.
NOTE 1 When tests are performed in vacuum or inert gas atmospheres, this maximal temperature gradient of 50 °C
in the controlled temperature zone is considered to be low enough to avoid large discrepancy of material behaviour in
the gauge length and then to bias the material properties determination.
NOTE 2 This value of 50 °C is a maximum value of the temperature gradient of the controlled temperature zone
especially for very high temperature test in cold grip configuration. If tests are performed at lower temperature,
temperature gradient lower than 50 °C can be easily achieved.
If the tests are performed under oxidative environment, for CMC materials which are sensitive to oxidative
degradation, the test duration and the controlled temperature zone thermal gradient parameters are to be
set at the lowest values possible in order to limit the impact on the material properties of the oxidative
degradation. For instance, for material such as CMC including a carbon interphase which are sensitive to
chemical degradation, it is recommended to not exceed ±5 °C below 500 °C for the temperature gradient
within the controlled temperature zone.
NOTE 3 An example of calibration method of test temperature and temperature gradient determination is
described in the Annex B.
5.5 Strain measurement
5.5.1 General
For continuous measurement of the longitudinal deformation as a function of the applied force at high
temperature, either suitable contacting or non-contacting extensometer may be used. Measurement of
longitudinal deformation over a length as long as possible within the controlled-temperature zone of the
test specimen is recommended.
5.5.2 Strain gauges
Strain gauges are used for the verification of the alignment on the test specimen at room temperature. They
are not recommended to determine longitudinal deformation during testing at high temperature.
5.5.3 Extensometer
5.5.3.1 General
The extensometer shall be capable of continuously recording the longitudinal deformation at test
temperature. The use of an extensometer with the greatest possible gauge length is preferable.
Extensometers shall meet the requirements of class 1 or less (class 0,5) in accordance with ISO 9513. Types
of commonly used extensometers are described in 5.5.3.2 and 5.5.3.3.

ISO 14544:2025(en)
5.5.3.2 Mechanical extensometer
For a mechanical extensometer, the gauge length shall be the initial longitudinal distance between the two
locations where the extensometer rods contact the test specimen.
The rods may be exposed to temperatures higher than the test specimen temperature. Temperature and/
or environment induced structural changes in the rod material shall not affect the accuracy of deformation
measurement. The material used for the rods shall be compatible with the test specimen material.
Any extensometer contact forces shall not introduce bending greater than that allowed in 5.2.
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. Verification may be done by measuring the
compressive modulus on a well-known material specimen.
Rod pressure onto the test specimen should be the minimum necessary to prevent slipping of the
extensometer rods.
5.5.3.3 Electro-optical extensometer
Electro-optical measurements in transmission require reference marks on the test specimen. For this
purpose, rods or flags shall be attached to the surface perpendicular to its axis. The gauge length shall be
the distance between the two reference marks. The material used for marks (and adhesive if used) shall be
compatible with the test specimen material and the test temperature and shall not modify the stress field in
the specimen.
NOTE 1 The use of integral flags as parts of the test specimen geometry is not preferred because of stress
concentration induced by such features.
NOTE 2 An electro-optical extensometer is not appropriate in the case where it’s impossible to distinguish the
colours of the reference marks and the test specimen.
5.5.3.4 Digital image correlation
Digital image correlation (DIC) method can be used for non-contacting strain field measurement. In order
to improve the measurement accuracy, the size of furnace window may be minimized and an optical filter
[2]
might be used to get high contrast random patterns at elevated temperatures .
NOTE Creating a flyspeck that can be used at high temperature is a major technical challenge with little or no
documentation to date.
Stress-strain response of ceramic composites can be determined for on-axis or off-axis compressive tests by
[2]
using DIC technique, as well as for tensile tests on SiC/SiC CMCs up to 1 316 °C .
Full-field deformation output procedure and calibration data shall be annexed to the test report.
5.6 Temperature measurement devices
For temperature measurement, either thermocouples conforming to IEC 60584-1 shall be used or, when
thermocouples not conforming to IEC 60584-1 or pyrometers are used, calibration data shall be annexed to
the test report.
5.7 Data recording system
A calibrated recorder may be used to record the force-deformation curve. The use of a digital data recording
system is recommended.
[3]
NOTE More detailed information is available in ISO 6892-1:2019, Annex A .

ISO 14544:2025(en)
5.8 Dimension measuring devices
Devices used for measuring linear dimensions of the test specimen shall be accurate to ±0,01 mm.
Micrometres shall conform to ISO 3611.
6 Test specimens
6.1 General
The choice of specimen geometry depends on several factors, such as:
— nature of the material and of the reinforcement structure;
— type of heating system;
— type of loading system.
The volume in the gauge length shall be representative of the material and calibrated length shall be chosen
such as to avoid buckling failure. If buckling occurs, it can be necessary to modify the dimensions of the test
specimen.
A test piece volume of a minimum of five representative volume elements is recommended. In the case of
off-axis loading conditions, results can depend on the cross-sectional area of specimens due to scale effect.
Two types of test specimens can be distinguished:
a) as-fabricated test specimens, where only the length and the width are machined to the specified size. In
this case, two faces of the test specimen can present irregular surfaces;
b) machined test specimens, where the length and the width, as well as the two faces of the test specimen,
have been machined and present regular machined surfaces.
Tolerance on the thickness dimension only applies to machined test specimens. For as-fabricated test
specimens, the difference in thickness out of three measurements (at the centre and at each end of the gauge
length) should not exceed 5 % of the average of the three measurements.
6.2 Compression between platens
The cross-sections of the recommended test specimens may be cylindrical, square or rectangular.
A Type 1 specimen is commonly used and is represented on Figure 1, where d and d represent the diameter,
t
side and short side respectively of the three specimen geometries.
Recommended dimensions are given in Table 1.

ISO 14544:2025(en)
Figure 1 — Type 1 specimen geometry
Table 1 — Recommended dimensions for a Type 1 specimen
Dimensions in millimetres
2D and xD Tolerance
l, calibrated length ≥ 15 ±0,5
l , total length ≥ 1,5 l ±0,5
t
d, circular or square section diameter or side length ≥ 8 ±0,2
d , circular or square section diameter or side length at the specimen base ≥ d+0,8r ±0,5
t
r, radius of shoulder ≥ 10 ≥ 2
Parallelism of machined parts 0,05
Perpendicularity of machined parts 0,05
Concentricity of machined parts 0,05
A Type 2 specimen is sometimes used and is represented in Figure 2. This specimen is mainly used when the
thickness of the part is not sufficient to machine a specimen of type 1.
Recommended dimensions are given in Table 2.

ISO 14544:2025(en)
Figure 2 — Type 2 specimen geometry
Table 2 — Recommended dimensions for a Type 2 specimen
Dimensions in millimetres
1D, 2D and xD Tolerance
l, calibrated length ≥ 10 ±0,5
d, circular or square section diameter or side length ≥ 10 ±0,2
Parallelism of machined parts 0,05
Perpendicularity of machined parts 0,05
6.3 Test specimen used with grips
For these types of specimens, the total length l depends on furnace and gripping system.
t
A Type 3 specimen is represented in Figure 3. This type of specimen is recommended in the case of buckling
with the specimen of Table 3. With this type of specimen, it is very difficult to obtain strain measurements.
Recommended dimensions are given in Tables 3 and 4.
Figure 3 — Type 3 specimen geometry

ISO 14544:2025(en)
Table 3 — Recommended dimensions for a Type 3 specimen
Dimensions in millimetres
2D and xD Tolerance
l, calibrated length ≥ 15 ±0,5
h, thickness ≥ 2 ±0,2
b , width in the calibrated length ≥ 8 ±0,2
b , width b = αb with α = 1,2 to 2 ±0,2
2 2 1
r, radius of shoulder ≥ 30 ±2
Parallelism of machined parts 0,05
Table 4 — Alternative recommended dimensions for a Type 3 specimen
Dimensions in millimetres
2D and xD Tolerance
l, calibrated length ≤ 15 ±0,5
h, thickness ≥ 1 ±0,2
b , width in the calibrated length ≥ 8 ±0,2
b , width b = αb with α = 1,2 to 2 ±0,2
2 2 1
r, radius of shoulder ≥ 30 ±2
Parallelism of machined parts 0,05
A Type 4 is sometimes used and is represented in Figure 4. When used with cold grips, this multi-section
specimen allows rupture within the controlled-temperature zone.
Recommended dimensions are given in Table 5.
Figure 4 — Type 4 specimen geometry

ISO 14544:2025(en)
Table 5 — Recommended dimensions for a Type 4 specimen
Dimensions in millimetres
2D and xD Tolerance
l, calibrated length ≥ 15 ±0,2
h, thickness 3 ±0,2
b , width in the calibrated length 8 to 20 ±0,2
b , width b = αb with α = 1,2 to 2 ±0,2
2 2 1
b , width b = βb with β = 1,2 to 2 ±0,2
3 3 2
r, radius of shoulder ≥ 30 ±2
Parallelism of machined parts 0,05
A Type 5 is sometimes used and is represented in Figure 5. This test specimen is easy to machine and its
use allows mainly the determination of modulus, as rupture may not happen in the controlled-temperature
zone; it should not be used for strength measurement
Recommended dimensions are given in Table 6.
Figure 5 — Type 5 specimen geometry
Table 6 — Recommended dimensions for a Type 5 specimen
Dimensions in millimetres
1D, 2D and xD Tolerance
h, thickness ≥ 2 ±0,2
b, width 8 to 20 ±0,2
Parallelism of machined parts 0,05
7 Test specimen preparation
7.1 Machining and preparation
During cutting out, care shall be taken to align the test specimen axis with the desired fibre related loading
axis. For off-axis tests, care shall be taken to determine the angle between main reinforcement and loading axis.
Machining methods that do not cause damage to material are recommended. Machining parameters should
be traceable.
ISO 14544:2025(en)
When specimens are machined from a plate which has been protected against oxidation, the cut surfaces of the
specimen are unprotected. These surfaces should be protected to prevent a possible oxidation under air test.
When a cold gripping system is used, the surface of the part of specimen which is at a temperature between
the test temperature and the grips temperature can need appropriate antioxidant protection.
7.2 Number of test specimens
At least three valid test results, as specified in 8.4 are recommended for any condition.
If statistical evaluation of the test results is required, the number of test specimens should be chosen
according to accepted statistical procedures and guidelines.
8 Test procedures
8.1 Test set-up: temperature considerations
8.1.1 General
The following determinations shall be carried out under conditions representative of the tests, and shall be
repeated every time there is a change, e.g. in material, in specimen geometry, in gripping configuration. In
establishing them, time shall be allowed for temperature stabilization.
8.1.2 Controlled-temperature zone
Prior to testing, the temperature gradient within the calibrated length inside the furnace shall be established
over the temperature range of interest in order to define the controlled temperature zone. This shall be
done if possible at test temperature (especially for very high temperature), by measuring the specimen
temperature at a minimum of three locations of the gauge length, which shall be the extensometer reference
points and midway between the two, and at least to other points outsid
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