EN ISO 19634:2026

SLOVENSKI STANDARD
01-april-2026
Fina keramika (sodobna keramika, sodobna tehnična keramika) - Keramični
kompoziti - Oznake in simboli (ISO 19634:2026)
Fine ceramics (advanced ceramics, advanced technical ceramics) - Ceramic composites
- Notations and symbols (ISO 19634:2026)
Hochleistungskeramik - Keramische Verbundwerkstoffe - Benennungen und
Formelzeichen (ISO 19634:2026)
Céramiques techniques - Céramiques composites - Notations et symboles (ISO
19634:2026)
Ta slovenski standard je istoveten z: EN ISO 19634:2026
ICS:
01.075 Simboli za znake Character symbols
81.060.30 Sodobna keramika Advanced ceramics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 19634
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2026
EUROPÄISCHE NORM
ICS 81.060.30 Supersedes EN ISO 19634:2021
English Version
Fine ceramics (advanced ceramics, advanced technical
ceramics) - Ceramic composites - Notations and symbols
(ISO 19634:2026)
Céramiques techniques - Céramiques composites - Hochleistungskeramik - Keramische
Notations et symboles (ISO 19634:2026) Verbundwerkstoffe - Benennungen und Formelzeichen
(ISO 19634:2026)
This European Standard was approved by CEN on 25 April 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
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 19634:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 19634:2026) 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 August 2026, and conflicting national standards shall
be withdrawn at the latest by August 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 19634:2021.
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 19634:2026 has been approved by CEN as EN ISO 19634:2026 without any modification.

International
Standard
ISO 19634
Second edition
Fine ceramics (advanced ceramics,
2026-02
advanced technical ceramics) —
Ceramic composites — Notations
and symbols
Céramiques techniques — Céramiques composites — Notations et
symboles
Reference number
ISO 19634:2026(en) © ISO 2026
ISO 19634:2026(en)
© ISO 2026
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 19634:2026(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Nomenclature and symbols . 4
4.1 Nomenclature .4
4.2 Symbols .5
5 Significance and use .13
5.1 Significance . . . 13
5.2 Use . 13

iii
ISO 19634:2026(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 19634:2017), which has been technically
revised.
The main changes are as follows:
— revision and addition of certain symbols and notations.
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.

iv
International Standard ISO 19634:2026(en)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Ceramic composites — Notations and symbols
1 Scope
This document specifies the symbols to be used to represent physical, mechanical and thermal characteristics,
as determined by methods described in relevant International Standards, for ceramic matrix composites.
This document also specifies the symbols used in undertaking measurements of these characteristics.
This document specifies symbols that are in accordance with the relevant parts of the ISO 80000 series
where possible.
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 80000-4, Quantities and units — Part 4: Mechanics
ISO 80000-5, Quantities and units — Part 5: Thermodynamics
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 80000-4 and ISO 80000-5 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
ceramic matrix composite
ceramic, carbon or glass matrix containing reinforcement distributed in one or more spatial directions
3.2
unidirectional ceramic matrix composite
1D material
ceramic matrix composite (3.1), the reinforcement of which is distributed in one single direction
Note 1 to entry: See Figure 1.

ISO 19634:2026(en)
Key
1 direction of reinforcement
2 direction of the greater transverse dimension (width), perpendicular to direction 1
3 direction of the smaller transverse dimension (thickness), perpendicular to direction 1
NOTE When the width and the thickness are equal, then directions 2 and 3 are equivalent and can be chosen
freely.
Figure 1 — Schematic diagram of a 1D material
3.3
in-plane reinforced ceramic matrix composite
2D material
ceramic matrix composite (3.1), where the reinforcements are placed along at least two directions in a single
plane
Note 1 to entry: See Figure 2.
Key
1 direction of the greater fraction of reinforcement
2 direction perpendicular to direction 1 in the plane of reinforcement (not necessarily a direction of
reinforcement)
3 direction perpendicular to the plane of reinforcement
NOTE Strictly more than one direction of fibrous reinforcement, all contained within one plane (in the present
case, there are three directions of reinforcement in plane (1,2)).

ISO 19634:2026(en)
When several directions have an equal fraction of reinforcement, it shall be stated which direction is chosen
as direction 1 in relation to the reinforcement structure (for example, orthogonal reinforced fabric: warp in
direction 1, weft in direction 2).
Figure 2 — Schematic diagram of a 2D material
3.4
multidirectional ceramic matrix composite
xD (2 < x ≤ 3) material
ceramic matrix composite (3.1), where the reinforcement is spatially distributed in at least three directions
not in a single plane
Note 1 to entry: See Figures 3 and 4.
Figure 3 — Schematic diagram of a xD (2 < × ≤ 3) material

ISO 19634:2026(en)
Key
1 direction of the greater fraction of reinforcement
2 direction perpendicular to direction 1
3 direction perpendicular to the plane containing directions 1 and 2
When several directions have equal fraction of reinforcement, it shall be stated which direction is chosen as
direction 1, in relation to the reinforcement structure. When it is possible to define a plane of reinforcement,
direction 2 will be chosen in this plane perpendicular to direction 1(direction 2 is not necessarily a direction
of reinforcement), and direction 3 will be perpendicular to the plane containing directions 1 and 2. When
it is not possible to define a plane of reinforcement, direction 2 is chosen arbitrarily, but perpendicular to
direction 1 and shall be clearly identified.
Figure 4 — Schematic diagram of a 3D material
4 Nomenclature and symbols
4.1 Nomenclature
Composites with continuous reinforcements constitute a specific class of these materials. Several subclasses
of ceramic matrix composites with continuous reinforcements can be distinguished.
The symbol F/I/M applies usually to ceramic matrix composites:
— F indicates the chemical nature of fibrous reinforcement: C stands for carbon, SiC for silicon carbide,
Al O for alumina, etc.
2 3
— I indicates the chemical nature of fibre/matrix interphase: C stands for carbon, BN for boron nitride,
LaPO for monazite, etc.
— M indicates the chemical nature of matrix: C for carbon, SiC for silicon carbide, Al O for alumina.
2 3
EXAMPLE 1 A ceramic matrix composite composed of a silicon carbide fibre, a carbon interphase and
...