ISO 20506:2005

INTERNATIONAL ISO
STANDARD 20506
First edition
2005-10-01
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Determination of the in-plane shear
strength of continuous-fibre-reinforced
composites at ambient temperature by
the Iosipescu test
Céramiques techniques — Détermination de la résistance au
cisaillement plan des composites renforcés de fibres continues à
température ambiante par l'essai de Iosipescu

Reference number
©
ISO 2005
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ii © ISO 2005 – All rights reserved

Contents Page
Foreword. iv
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Symbols and designations . 2
5 Principle. 3
6 Interferences. 4
6.1 Test environment. 4
6.2 Preparation of test pieces. 4
6.3 Failures outside gauge section . 4
6.4 Clamping forces. 4
6.5 Friction. 4
6.6 Thin test pieces. 4
7 Apparatus. 4
7.1 Testing machines. 4
7.2 Data acquisition . 5
7.3 Dimension-measuring devices. 5
7.4 Test fixture. 5
8 Test piece. 6
8.1 Test piece geometry. . 6
8.2 Test piece preparation. 6
8.2.1 Customary practices. 6
8.2.2 Standard procedures. 7
8.2.3 Handling precautions . 7
8.3 Number of test pieces . 7
9 Precautionary statement. 7
10 Test conditions . 7
10.1 Test modes and rates. 7
10.1.1 Displacement rate. 7
10.1.2 Load rate. 8
11 Procedure. 8
11.1 Test piece dimensions . 8
11.2 Preparations for testing . 8
11.3 Conducting the test . 8
11.3.1 Mount the test piece in the test fixture. 8
11.3.2 Begin data acquisition. 9
11.3.3. Initiate the action of the test machine . 9
11.4 Completion of testing. 9
11.5 Post test. 11
12 Calculation of results . 11
12.1 Shear strength. 11
12.2 Statistics. 11
13 Test report. 12
Annex A (informative) Results of round-robin tests. 13
Bibliography . 15
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 20506 was prepared by Technical Committee ISO/TC 206, Fine ceramics.

iv © ISO 2005 – All rights reserved

INTERNATIONAL STANDARD ISO 20506:2005(E)

Fine ceramics (advanced ceramics, advanced technical
ceramics) — Determination of the in-plane shear strength of
continuous-fibre-reinforced composites at ambient temperature
by the Iosipescu test
1 Scope
This International Standard specifies a method for the determination of in-plane shear strength of continuous-
fibre-reinforced ceramic composites at ambient temperature by the Iosipescu test. Methods for test piece
fabrication, testing modes and rates (load rate or displacement rate), data collection, and reporting procedures
are addressed.
This International Standard applies primarily to advanced ceramic or glass-matrix composites with continuous-
fibre reinforcement having uni-directional (1-D), bi-directional (2-D) or 3-D fibre architecture. This test method
does not address composites with discontinuous-fibre-reinforced, whisker-reinforced or particulate-reinforced
ceramics.
NOTE 1 Values expressed in this International Standard are in accordance with the International System of Units (SI).
NOTE 2 This International Standard is based on ASTM C1292.
2 Normative references
The following referenced documents are indispensable for the application 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, Micrometer callipers for external measurement
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
ASTM C1292, Standard Test Method for Shear Strength of Continuous Fiber-Reinforced Advanced Ceramics
at Ambient Temperatures
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply:
3.1
fine ceramic (advanced ceramic, advanced technical ceramic)
highly engineered, high-performance predominately non-metallic, inorganic, ceramic material having specific
functional attributes
3.2
continuous-fibre-reinforced ceramic composite
CFCC
ceramic matrix composite in which the reinforcing phase consists of a continuous fibre, continuous yarn, or a
woven fabric
3.3
shear failure load
maximum load required to fracture a shear-loaded test piece
3.4
shear strength
maximum shear stress which a material is capable of sustaining
NOTE Shear strength is calculated from the shear-fracture load and the shear-loaded area.
4 Symbols and designations
Symbols used throughout this International Standard and their designations are given in Table 1.
Table 1 — Symbols and designations
Symbol Designation Unit References
L Test piece length mm Table 2
Table 2
h Distance between notches mm
Equation 2
w Test piece width mm Table 2
Table 2
t Test piece thickness mm
Equation 2
R Notch radius mm Table 2
Notch angle ° Table 2
θ
n Number of valid tests 1 Equations 3, 4
P
Maximum load N Equation 1
max
A Shear area of test piece Equation 1
mm
τ
In-plane shear strength MPa Equation 1
IP
mean MPa Equation 3, 4, 5
X
SD standard deviation MPa Equation 4
CV Coefficient of variation 1 Equation 5
2 © ISO 2005 – All rights reserved

5 Principle
This International Standard is for material development, material comparison, quality assurance,
characterization, reliability and design data generation. The in-plane shear strength of continuous-fibre-
reinforced ceramic composites, as determined by this International Standard, is measured by the Iosipescu
test. According to this test, the shear strength is determined by loading a test coupon in the form of a
rectangular flat strip with symmetric, centrally located V-notches using a mechanical testing machine and a
modified asymmetric four-point bending fixture. Failure of the test piece occurs by shear between the
V-notches. Schematics of the test setup and the test piece are shown in Figures 1 and 2.

Figure 1 — Schematic of Iosipescu test piece subjected to asymmetric four-point bending

Dimensions in millimetres
Figure 2 — Geometry and dimensions of Iosipescu test piece
6 Interferences
6.1 Test environment
The test environment may have an influence on the measured shear strength. In particular, the behaviour of
materials susceptible to slow-crack-growth fracture will be strongly influenced by the test environment and
testing rate. Testing to evaluate the maximum strength potential of a material shall be conducted in inert
environments and/or at sufficiently rapid testing rates, so as to minimize slow-crack-growth effects.
Conversely, testing can be conducted in environments and testing modes and rates representative of service
conditions to evaluate material performance under those conditions. When testing is conducted in
uncontrolled ambient air with the objective of evaluating maximum strength potential, relative humidity and
temperature shall be monitored and reported.
6.2 Preparation of test pieces
Preparation of test pieces, although normally not considered a major concern with continuous-fibre-reinforced
ceramic composites, can introduce fabrication flaws which may have pronounced effects on the mechanical
properties and behaviour (e.g. shape and level of the resulting load-displacement curve and shear strength).
Machining damage introduced during test piece preparation can be either a random interfering factor in the
determination of shear strength of pristine material, or an inherent part of the strength characteristics to be
measured. Universal or standardized test methods of surface preparation do not exist. Final machining steps
may, or may not, negate machining damage introduced during the initial machining. Thus, the history of the
test piece fabrication may play an important role in the measured strength distributions and shall be reported.
6.3 Failures outside gauge section
Fractures that initiate outside the uniformly stressed gauge section of a test piece may be due to extraneous
stresses introduced by improper loading configurations, or strength-limiting features in the microstructure of
the test piece. Such non-gauge section fractures will constitute invalid tests.
6.4 Clamping forces
Excessive clamping force will induce undesirable pre-loading and may damage some materials.
6.5 Friction
Most fixtures for the Iosipescu test incorporate an alignment mechanism in the form of a guide rod and a linear
roller bearing. Excessive free play or excessive friction in this mechanism may introduce spurious moments
that will alter the ideal loading conditions.
6.6 Thin test pieces
Thin test pieces (width to thickness ratio of more than 10) may suffer from splitting and instabilities rendering,
in turn, invalid test results.
7 Apparatus
7.1 Testing machines
The testing machine shall be verified in accordance with ISO 7500-1 and shall be at least grade 1,0.
4 © ISO 2005 – All rights reserved

7.2 Data acquisition
Obtain at least an autographic record of applied load and cross-head displacement versus time using either
analogue chart recorders or digita
...