ISO 21113:2018

Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for fracture toughness of monolithic ceramic thin plates at room temperature

This document describes a test method for the determination of the fracture toughness of monolithic ceramic thin plates at room temperature by the single-edge precracked plate method or the single-edge V-notch plate method. This document is intended for use with monolithic ceramics and whisker- or particulate-reinforced ceramics which are regarded as macroscopically homogeneous. It does not include continuous-fibre-reinforced ceramics composites. This document is applicable to ceramic thin plates with a thickness of 0,2 mm to The single-edge V-notch plate method can be applied to monolithic ceramics with a grain size larger than about 1 μm. The use of this method is inappropriate for yttria tetragonal zirconia polycrystal material (Y-TZP), which consists of homogeneous fine submicron grains. The method might also be unsuitable for some other very tough or soft ceramics in which a sharp crack does not form at the root of the V-notch. This document is for material development, material comparison, quality assurance, characterization, reliability and design data generation.

Céramiques techniques (céramiques avancées, céramiques techniques avancées) — Méthode d’essai pour déterminer la ténacité des plaques minces en céramique monolithique à température ambiante

General Information

• Status: Published
• Publication Date: 16-Jul-2018
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: ISO/TC 206 - Fine ceramics
• Drafting Committee: ISO/TC 206 - Fine ceramics
• Current Stage: 9092 - International Standard to be revised
• Start Date: 03-Oct-2024
• Completion Date: 12-Feb-2026

Overview

ISO 21113:2018 specifies a standardized laboratory test method for determining the fracture toughness of monolithic ceramic thin plates at room temperature. It covers two specimen-based approaches: the single-edge precracked plate (SEPP) method and the single-edge V‑notch plate (SEVNP) method. The standard applies to monolithic ceramics and whisker- or particulate-reinforced ceramics regarded as macroscopically homogeneous (plate thickness 0.2 mm to <1.0 mm) and excludes continuous-fibre‑reinforced ceramic composites.

Key Topics and Technical Requirements

• Test methods: Three‑ or four‑point bending fracture tests on precracked or V‑notched rectangular plate specimens.
• Specimen geometry & tolerances:
  • Width typically 4.0 ± 0.2 mm; length ≥ 36 mm or ≥ 45 mm depending on configuration; thickness 0.2–1.0 mm.
  • Parallelism tolerance on long faces: 0.015 mm; perpendicularity tolerance: 0.01 mm; thickness variation < 10% of average.
• Precrack and notch preparation:
  • SEPP: a straight-through pop‑in precrack induced by three‑point bending of a saw‑notched specimen bonded to a brass beam (detailed preparation in Annex A).
  • SEVNP: sharp V‑notch machined using a reciprocating razor blade with diamond paste (Annex B); V‑notch method recommended only for materials with grain sizes ≳1 μm.
  • Notch‑root radius should be similar to or less than twice the average grain size; V‑notch unsuitable for Y‑TZP and some very tough/soft ceramics that do not form a sharp crack.
• Apparatus & measurement:
  • Test machine accuracy per ISO 7500‑1 (force accuracy 1%); crosshead speed typically 0.5 mm/min.
  • Roller pin diameters 4.0–5.0 mm; roller surface roughness Ra ≤ 0.4 μm.
  • Measure fracture load, specimen dimensions and precrack/notch length; precrack length measurement and validity assessment described in Annex C.
• Data analysis:
  • Fracture toughness (KIC) is calculated from fracture load, specimen geometry and a stress‑intensity shape factor (Y). The standard gives specific formulae, acceptance criteria and statistical reporting (mean and standard deviation). Minimum specimen counts and validity rules are specified (prepare ≥8 specimens; ≥5 valid results required).

Applications

ISO 21113:2018 is intended for:

• Material development and R&D - comparing toughness of fine‑ceramic formulations.
• Quality assurance and production control - routine verification of fracture properties for thin ceramic plates.
• Characterization, reliability and design data - providing KIC values for component design and failure assessment. Who uses it: materials scientists, ceramic engineers, test laboratories, QA teams, and designers of advanced ceramic components (electronic substrates, sensors, wear parts, thin structural ceramics).

Related standards

• ISO 15732 - fracture toughness by single‑edge precracked beam (SEPB) method (reference within ISO 21113).
• ISO 7500‑1 - verification/calibration of force measurement for testing machines.

Keywords: ISO 21113:2018, fracture toughness, monolithic ceramic thin plates, single-edge precracked plate, single-edge V-notch plate, fine ceramics, advanced ceramics, test method, room temperature.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 21113
First edition
2018-07
Fine ceramics (advanced ceramics,
advanced technical ceramics) — Test
method for fracture toughness of
monolithic ceramic thin plates at
room temperature
Céramiques techniques (céramiques avancées, céramiques techniques
avancées) — Méthode d’essai pour déterminer la ténacité des plaques
minces en céramique monolithique à température ambiante
Reference number
©
ISO 2018
© ISO 2018
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
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CH-1214 Vernier, Geneva
Phone: [phone]
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Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
5.1 Bend testing machine. . 2
5.2 Bend test fixture. . 2
6 Test piece dimension and preparation. 4
6.1 Shape and dimensions of test piece . 4
6.2 Test piece preparation . 5
6.3 Number of test piece . 5
7 Test methods . 5
7.1 Three or four-point bending fracture test . 5
7.2 Measurement of thickness and width of test piece . 5
7.3 Measurement of precrack length . 5
8 Evaluation of validity of measured value . 5
9 Calculation . 6
10 Test report . 7
Annex A (normative) Test piece preparation for the precracked plate method .8
Annex B (normative) Test piece preparation for the V-notch plate method .13
Annex C (normative) Measurement of precrack length and evaluation of validity of
measured value for the precracked plate method .19
Bibliography .21
Foreword
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This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 21113:2018(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for fracture toughness of
monolithic ceramic thin plates at room temperature
1 Scope
This document describes a test method for the determination of the fracture toughness of monolithic
ceramic thin plates at room temperature by the single-edge precracked plate method or the single-edge
V-notch plate method.
This document is intended for use with monolithic ceramics and whisker- or particulate-reinforced
ceramics which are regarded as macroscopically homogeneous. It does not include continuous-fibre-
reinforced ceramics composites. This document is applicable to ceramic thin plates with a thickness of
0,2 mm to <1,0 mm.
The single-edge V-notch plate method can be applied to monolithic ceramics with a grain size larger
than about 1 μm. The use of this method is inappropriate for yttria tetragonal zirconia polycrystal
material (Y-TZP), which consists of homogeneous fine submicron grains. The method might also be
unsuitable for some other very tough or soft ceramics in which a sharp crack does not form at the root
of the V-notch.
This document is for material development, material comparison, quality assurance, characterization,
reliability and design data generation.
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 1101, Geometrical Product Specifications (GPS) — Geometrical tolerancing — Tolerances of form,
orientation, location and run-out
ISO 4287, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Terms, definitions
and surface texture parameters
ISO 7500-1, Metallic materials — Verification of static uniaxial testing machines — Part 1: Tension/
compression testing machines — Verification and calibration of the force-measuring system
ISO 15732, Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for fracture
toughness of monolithic ceramics at room temperature by single edge precracked beam (SEPB) method
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 15732 apply.
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/
4 Principle
This method is to obtain the fracture toughness value from the precrack length or the V-notch depth,
specimen dimensions and distance between the bending supports by measuring the fracture load of
specimen according to the three- or four-point bending fracture test of a single-edge precracked plate
specimen or a V-notched plate specimen. For the single-edge precracked plate method, a straight-
through pop-in precrack is induced in the specimen via three-point bending a saw-notched test
specimen bonded to a brass beam. For the V-notch plate method, a sharp-tipped notch is machined
using the technique of a reciprocating razor blade and diamond paste.
The use of the single-edge V-notch plate method for materials with grain size less than 1 μm is not
recommended, since the assumption that the notch approximates to a sharp crack is not established.
Users should strive to minimize the notch-root radius in the test pieces. This document places a
provisional criterion that the notch-root radius should be similar to or less than twice the average grain
size of the material.
5 Apparatus
5.1 Bend testing machine.
A suitable testing machine capable of applying a uniform cross-head speed shall be used. The testing
machine shall be in accordance with ISO 7500-1, with an accuracy of 1 % of the indicated force at
fracture.
5.2 Bend test fixture.
The general features of the bend test fixture are illustrated in Figure 1. The bend test fixture shall be
symmetrical about the centre line shown. The fixture shall have a thin slit in which the test specimen
can stand vertically on the supporting roller pins. The width of the slit shall be about 0,03 mm larger
than the specimen thickness. The loading roller pin for the three-point bend test is placed in the
positioning groove of the supporting member as shown in Figure 1 (a). The width of the positioning
groove should be about 0,05 mm larger than the diameter of the roller pin. The left and right loading
roller pins for the four-point bend test are placed in each positioning groove of the supporting member
as shown in Figure 1 (b) and are held against the stops and pillars. For both three-point and four-point
bend tests, the supporting roller pins are held against the stops and pillars. The loading member has a
tooth, which is put in the longitudinal groove of the supporting member to prevent the loading roller pin
from tilting so that it can push the specimen vertically. Other types of fixtures are acceptable; however,
compression force shall be applied vertically on the top surface of the specimen. Materials composing
the parts of the roller pins to be used shall be made of a material free from plastic deformation and risk
of fracture. The diameter of loading roller pin and supporting roller pins shall be between 4,0 mm and
5,0 mm. The surface roughness of the rollers, Ra, as defined in ISO 4287 shall be not more than 0,4 μm.
2 © ISO 2018 – All rights reserved

a) Three-point bend test fixture
b) Four-point bend test fixture
Key
1 loading ball 7 precrack or V notch
2 loading member with round head 8 supporting roller pins
3 loading member 9 stops and pillars
4 tooth of the loading member 10 supporting member
5 loading roller pins 11 longitudinal groove for the tooth of the loading member
6 specimen 12 slit for the specimen
Support span Loading span
Diameter of roller
pins
Bending mode Specimen d d
1 2
mm mm mm
3-point bend I 4,0 to 5,0 30 ± 0,3 —
4-point bend I 4,0 to 5,0 30 ± 0,3 10 ± 0,2
4-point bend II 4,0 to 5,0 40 ± 0,4 20 ± 0,2
Figure 1 — Bend test fixtures
6 Test piece dimension and preparation
6.1 Shape and dimensions of test piece
Prepare plate test pieces of rectangular cross-section. Figure 2 shows the shape and main dimensions of
the test pieces. The parallelism tolerance on the opposite longitudinal side L × B face shall be 0,015 mm
as defined in ISO 1101. The longitudinal side faces shall intersect with the large faces perpendicularly.
The maximum variation in perpendicularity shall not exceed 0,01 mm. The variation of thickness, B –
max
B , shall be less than 10 % of the average thickness, B , which is determined from the thicknesses at
min ave
three or more points.
Total length Width Thickness
Specimen L W B
mm mm mm
I ≥36 4,0 ± 0,2 0,2 to 1,0
II ≥45 4,0 ± 0,2 0,2 to 1,0
Figure 2 — Dimensions of specimen
The longitudinal side L × B faces of as-cut thin plate usually intersect with the large face at a slightly
oblique angle or have burrs and/or chippings as described in Figure 3. Both cross section and the
longitudinal side L × B faces shall be observed with an optical microscope at a magnification of about
20 × or greater. The longitudinal side faces shall be polished until they form a right angle to the large
surfaces.
Figure 3 — Guidelines for the unacceptable cross sections of specimen
It is recommended that the cut specimen width is slightly larger than 4,0 mm taking into account
the reserving space for polishing. It is also recommended that the length, L, of the test piece is kept
constant, for example 40 mm ± 0,2 mm, unless special requests exist. Otherwise, different brass beams
with stops need to be made for the ease of centring of the notch and precrack in the fixture every time
the length of the test piece is changed.
4 © ISO 2018 – All rights reserved

6.2 Test piece preparation
Machining aspects unique to the precracked method and V-notched method shall be used as specified
in Annexes A and B, respectively.
6.3 Number of test piece
At least eight test pieces shall be prepared for a flexural-strength test, of which five are required for
valid results.
7 Test methods
7.1 Three or four-point bending fracture test
7.1.1 Insert the test piece into the slit of the test jig slowly, with the precracked or V-notched face on
the outer-support rollers as shown in Figure 1. Ensure that the precrack is on the centre of supporting
roller pins to within ± 0,1 mm. Set the loading roller pin(s) on the specimen and hold the pin(s) until
the loading member is placed on it, otherwise the loading roller pin(s) will drop off. When the loading
member is positioned, turn the loading member so that the tooth fits in the longitudinal groove of the
support member. If the tooth of the loading member is out of the longitudinal groove, the loading member
and loading roller will tilt slightly, and compressive force will be applied obliquely to the test specimen.
7.1.2 Apply a compressive load to the loading member at a cross-head speed of 0,5 mm/min until the
specimen fractures, and measure the maximum load, P , to an accuracy of 1 %.
f
7.2 Measurement of thickness and width of test piece
The measurement of the thickness and width of the specimen shall be carried out using a micrometer
or other device accurate to the nearest 0,01 mm.
7.3 Measurement of precrack length
For the single-edge precracked plate method, measure the precrack length of the test piece after
fracture as specified in Annex C.
8 Evaluation of validity of measured value
A valid test shall meet the requirements specified in Annexes B and C.
9 Calculation
Calculate the fracture toughness value, K or K , from the measured values for each specimen
Ipp Ic,SEVNP
according to Formulae (1) to (4). Obtain the average value of fracture toughness of five or more
specimens conforming to the specification given in Clause 8 and round off to one decimal place.
Pd× 3
 
12/
f 1
KorK = αα×Y (1)
()
IppIc,SEVNP
 
32/
BW×  
where, in the case of three-point bend specimen I,
23 4
Y()α =+1,,964−2,837αα13 711 −23,250αα+24,129 (2)
In the case of four-point bend specimen I and II,
12/
 
Pd×()−d
3 α
f 12
KorK = ×Y α (3)
 ()
IppIc,SEVNP
32/ 32/
BW×  (1−)α 
 
(,3490−−,,68αα+1351)(αα)
Y()αα= , −1,326 − (4)
1 9877
()1+α
where
1/2
K is the fracture toughness, single-edge precracked plate method, in MPa·m ;
Ipp
1/2
K is the fracture toughness, single-edge V-notch plate method, in MPa·m ;
Ic,SEVNP
P is the fracture load, in MN;
f
B is the specimen thickness, in m;
W is the specimen width, in m;
d is the support span, in m;
d is the loading span (d > d ), in m;
2 1 2
α is the average relative precrack length or the average relative V-notch depth;
Y is the stress intensity shape factor.
The mean fracture toughness, K or K , and the standard deviation, s, are given by
Ipp Ic,SEVNP
Formulae (5) and (6), respectively.
6 © ISO 2018 – All rights reserved

n n
K K
∑ Ipp,i ∑ Ic,SEVNP,i
1 1
K = or K = (5)
Ipp Ic,SEVNP
n n
12/ 12/
n n
   
2 2
   
()KK− ()KK−
Ipp Ic,SEVNP
∑ Ipp,i ∑ Ic,SEVNP,i
   
1 1
s= or s= (6)
   
n−1 n−1
   
   
   
where
K is the fracture toughness of the ith specimen, single-edge precracked plate method;
Ipp,i
K is the fracture toughness of the ith specimen, single-edge V-notch plate method;
Ic,SEVNP,i
n is the total number of specimens.
10 Test report
The test report shall include the following information:
a) type of material, code, batch number, date of manufacture;
b) type of test method (either single-edge precrack plate method or single-edge V-notch plate method);
c) number of specimens conforming to the specifications given in Clause 8;
d) measured fracture toughness values, K or K , the average and the standard deviation, in
Ipp Ic,SEVNP
megapascal metres to the power half;
e) specimen dimensions: thickness, B, width, W, in millimetres;
f) precracking conditions (e.g. depth and width of notch and pop-in load) or a description of the
method employed to prepare the V-notches;
g) environment conditions, relative humidity and temperature;
h) maximum load before fracture, P , in newtons;
f
i) precrack lengths, l, in millimetres, or depth of the V-notches, a, notch-root width, S, in millimetres,
and V-notch angle, β.
Annex A
(norm
...