EN ISO 17138:2025

Fine ceramics (advanced ceramics, advanced technical ceramics) - Mechanical properties of ceramic composites at room temperature - Determination of flexural strength (ISO 17138:2025)

This document specifies a test method for the determination of the flexural strength of ceramic matrix composite materials with continuous fibre reinforcement, under three-point or four-point bend at room temperature. This document is applicable to all ceramic matrix composites with a continuous fibre reinforcement, unidirectional (1D), bidirectional (2D), and tridirectional xD with (2 < x ≤ 3) as defined in ISO 19634, loaded along one principal axis of reinforcement.

Hochleistungskeramik - Mechanische Eigenschaften von keramischen Verbundwerkstoffen bei Raumtemperatur - Bestimmung der Biegefestigkeit (ISO 17138:2025)

Céramiques techniques - Propriétés mécaniques des composites céramiques à température ambiante - Détermination de la résistance en flexion (ISO 17138:2025)

Le présent document spécifie une méthode d’essai permettant de déterminer la résistance en flexion des matériaux composites à matrice céramique et à renforts de fibres continus par un essai de flexion en trois ou quatre points à température ambiante. Le présent document s’applique à tous les composites à matrice céramique à renforts de fibres continus, unidirectionnels (1D), renforcés dans le plan (2D) et multidirectionnels xD avec (2 < x ≤ 3), conformément à l'ISO 19634, sollicités suivant un axe principal de renfort.
Le présent document n'est pas destiné à être utilisé pour obtenir des valeurs absolues de résistance pour le dimensionnement.

Fina keramika (sodobna keramika, sodobna tehnična keramika) - Mehanske lastnosti keramičnih kompozitov pri sobni temperaturi - Ugotavljanje upogibne trdnosti (ISO 17138:2025)

General Information

• Status: Published
• Publication Date: 11-Nov-2025
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: CEN/TC 184 - Advanced technical ceramics
• Drafting Committee: CEN/TC 184/SC 1 - Ceramic composites
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 12-Nov-2025
• Completion Date: 12-Nov-2025
• Ref Project: SIST EN ISO 17138:2026 - Fine ceramics (advanced ceramics, advanced technical ceramics) - Mechanical properties of ceramic composites at room temperature - Determination of flexural strength (ISO 17138:2025)

Relations

• Replaces: EN ISO 17138:2022 - Fine ceramics (advanced ceramics, advanced technical ceramics) - Mechanical properties of ceramic composites at room temperature - Determination of flexural strength (ISO 17138:2014)
• Effective Date: 15-Nov-2023

Overview

EN ISO 17138:2025 (CEN adoption of ISO 17138:2025) specifies a standardized test method to determine the flexural strength of ceramic matrix composites (CMCs) with continuous fibre reinforcement at room temperature. The method covers both three-point and four-point bend configurations and applies to unidirectional (1D), bidirectional (2D) and tridirectional (xD where 2 < x ≤ 3) reinforced CMCs as defined in ISO 19634. The document is intended for characterization and comparative testing rather than for establishing absolute design values.

Key topics and requirements

• Scope and applicability: Test method for CMCs with continuous fibres loaded along one principal reinforcement axis; room-temperature testing only.
• Test configurations: Procedures for three-point and four-point bending tests, including specimen mounting and loading geometry.
• Apparatus and measurement: Requirements for test machines, fixtures, data recording systems and dimensional measuring devices (references include ISO 7500-1 and ISO 3611).
• Specimen preparation: Machining, dimensional measurement and the required number of test specimens for valid results.
• Test procedures: Guidance on displacement rate, measurement of specimen dimensions and distances between supports, and test technique.
• Result calculation and validity: Calculation of flexural stress and flexural strength for both 3‑point and 4‑point tests, plus criteria for test validity and reporting.
• Limitations: The standard highlights that classical elastic beam theory assumptions do not always hold for CMCs (damage-induced non-linear deformation and atypical fracture modes), so bending tests are limited as absolute strength predictors.

Applications

• Materials research & development: Comparative strength evaluation of advanced ceramics and ceramic composites during material development.
• Quality control: Routine testing for batch-to-batch consistency in manufacturing of CMC components.
• Laboratory characterization: Standardized method for inter-lab comparison of flexural performance data.
• Academic testing: Research into failure modes, fracture behavior and reinforcement effects in advanced ceramics.

Typical users include materials engineers, ceramics laboratories, R&D teams, manufacturers of CMC components, and certification bodies focused on advanced technical ceramics.

Related standards

• ISO 19634 - Notations and symbols for ceramic composites (defines reinforcement types referenced).
• ISO 7500-1 - Calibration and verification of force-measuring systems for test machines.
• ISO 3611 - Metrological requirements for micrometers and dimensional instruments.

Keywords: EN ISO 17138:2025, flexural strength, ceramic matrix composites, CMC, three-point bend, four-point bend, advanced ceramics, mechanical properties, test method.

Standards Content (Sample)

SLOVENSKI STANDARD
01-januar-2026
Fina keramika (sodobna keramika, sodobna tehnična keramika) - Mehanske
lastnosti keramičnih kompozitov pri sobni temperaturi - Ugotavljanje upogibne
trdnosti (ISO 17138:2025)
Fine ceramics (advanced ceramics, advanced technical ceramics) - Mechanical
properties of ceramic composites at room temperature - Determination of flexural
strength (ISO 17138:2025)
Hochleistungskeramik - Mechanische Eigenschaften von keramischen
Verbundwerkstoffen bei Raumtemperatur - Bestimmung der Biegefestigkeit (ISO
17138:2025)
Céramiques techniques - Propriétés mécaniques des composites céramiques à
température ambiante - Détermination de la résistance en flexion (ISO 17138:2025)
Ta slovenski standard je istoveten z: EN ISO 17138:2025
ICS:
81.060.30 Sodobna keramika Advanced ceramics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 17138
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2025
EUROPÄISCHE NORM
ICS 81.060.30 Supersedes EN ISO 17138:2022
English Version
Fine ceramics (advanced ceramics, advanced technical
ceramics) - Mechanical properties of ceramic composites
at room temperature - Determination of flexural strength
(ISO 17138:2025)
Céramiques techniques - Propriétés mécaniques des Hochleistungskeramik - Mechanische Eigenschaften
composites céramiques à température ambiante - von keramischen Verbundwerkstoffen bei
Détermination de la résistance en flexion (ISO Raumtemperatur - Bestimmung der Biegefestigkeit
17138:2025) (ISO 17138:2025)
This European Standard was approved by CEN on 6 June 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 17138:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 17138:2025) 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 May 2026, and conflicting national standards shall be
withdrawn at the latest by May 2026.
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 17138:2022.
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 17138:2025 has been approved by CEN as EN ISO 17138:2025 without any modification.

International
Standard
ISO 17138
Second edition
Fine ceramics (advanced ceramics,
2025-11
advanced technical ceramics) —
Mechanical properties of ceramic
composites at room temperature —
Determination of flexural strength
Céramiques techniques — Propriétés mécaniques des composites
céramiques à température ambiante — Détermination de la
résistance en flexion
Reference number
ISO 17138:2025(en) © ISO 2025
ISO 17138:2025(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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 17138:2025(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Significance and use . 2
5 Principle . 2
6 Apparatus . 2
6.1 Test machine .2
6.2 Test fixture .2
6.3 Data recording system .3
6.4 Dimension measuring devices .4
7 Test specimens . 4
8 Test specimen preparation . 4
8.1 Machining and preparation .4
8.2 Number of test specimens .5
9 Test procedures . 5
9.1 Displacement rate .5
9.2 Measurement of dimensions .5
9.2.1 Test specimen dimensions .5
9.2.2 Distances between supporting rollers.5
9.3 Testing technique .5
9.3.1 Test specimen mounting .5
9.3.2 Measurements .6
9.4 Test validity .6
9.5 Calculation of results .6
9.5.1 General .6
9.5.2 Three-point bend .6
9.5.3 Four-point bend .7
10 Test report . 7
Bibliography . 8

iii
ISO 17138:2025(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,
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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.
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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 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 17138:2014) which has been technically
revised.
The main changes are as follows:
— Clause 2 updated;
— Clause 4 on Significance and use added;
— Clause 10 updated;
— editorially revised.
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.

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