ISO 20505:2005

INTERNATIONAL ISO
STANDARD 20505
First edition
2005-10-01
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Determination of the interlaminar shear
strength of continuous-fibre-reinforced
composites at ambient temperature by
the compression of double-notched test
pieces and by the Iosipescu test
Céramiques techniques — Détermination de la résistance au
cisaillement interlaminaire des composites renforcés de fibres connues
à température ambiente par compression d'éprouvettes doublement
entaillées et par l'essai de Iosipescu

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

Contents Page
Foreword. v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Symbols and abbreviated terms .2
5 Principle.3
6 Interferences.5
6.1 Test environment.5
6.2 Preparation of test pieces.5
6.3 Bending.5
6.4 Failures outside gauge section.6
6.5 Notch separation.6
6.6 Specimen clamping.6
6.7 Friction.6
7 Apparatus.6
7.1 Testing machines.6
7.2 Data acquisition .6
7.3 Dimension-measuring devices.6
7.4 Test fixtures.7
8 Test piece.10
8.1 Test piece geometry .10
8.1.1 Double-notched test piece.10
8.1.2 Iosipescu test piece.10
8.2 Test piece preparation .11
8.2.1 Customary practices.11
8.2.2 Standard procedures.11
8.2.3 Handling precautions .12
8.3 Number of test pieces .12
9 Precautionary statement.12
10 Test conditions .12
10.1 Test modes and rates.12
10.1.1 Displacement rate.12
10.1.2 Load rate.12
11 Procedure.12
11.1 Test piece dimensions .12
11.2 Preparations for testing .13
11.3 Conducting the test .13
11.3.1 Mount the test piece in the test fixture.13
11.3.2 Begin data acquisition. .13
11.4 Completion of testing.14
11.5 Post test.15
12 Calculation of results .15
12.1 Shear strength.15
12.1.1 Double-notched test piece.15
12.1.2 Iosipescu test piece.15
12.2 Statistics.16
13 Test report. 16
Annex A (informative) Results of round-robin tests . 18
Bibliography . 20

iv © ISO 2005 – All rights reserved

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 20505 was prepared by Technical Committee ISO/TC 206, Fine ceramics.

INTERNATIONAL STANDARD ISO 20505:2005(E)

Fine ceramics (advanced ceramics, advanced technical
ceramics) — Determination of the interlaminar shear strength of
continuous-fibre-reinforced composites at ambient temperature
by the compression of double-notched test pieces and by the
Iosipescu test
1 Scope
This International Standard specifies a method for the determination of interlaminar shear strength of
continuous-fibre-reinforced ceramic composites at ambient temperature, by the compression of a double-
notched test piece or 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) or bi-directional (2-D) fibre architecture. This test method does
not address composites with (3-D) fibre architecture or 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 abbreviated terms
The 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 Tables 2, 3
Tables 2, 3
h Distance between notches mm
Equations 2, 4
Tables 2, 3
w Test piece width mm
Equation 2
Tables 2, 3
t Test piece thickness mm
Equation 4
d Notch width, double-notched test piece mm Table 2
R
Notch radius, Iosipescu test piece mm Table 3
Θ Notch angle, Iosipescu test piece ° Table 3
Equations 5, 6
n Number of valid tests 1
subclause 12.2
P
Maximum load N Equations 1, 3
max
A
Shear area for double-notched test piece Equations 1, 2
mm
A
Shear area for Iosipescu test piece mm Equations 3, 4
τ
Interlaminar shear strength MPa Equations 1, 3
IL
Mean value MPa Equations 5, 6, 7
X
SD Standard deviation MPa Equations 6, 7

CV Coefficient of variation 1 Equation 8

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 interlaminar shear strength of continuous-fibre-
reinforced ceramic composites, as determined by this International Standard, can be measured by the
compression of double-notched test pieces or by the Iosipescu test. In the case of the former, a double-
notched test piece of uniform width is loaded in compression to induce failure by shear between two centrally
located notches machined halfway through the thickness and spaced a fixed distance apart on opposing faces.
Schematics of the test setup and the test piece are shown in Figures 1 and 2.

Figure 1 — Schematic of double-notched test piece subjected to compressive loading
Dimensions in millimetres
Figure 2 — Geometry and dimensions of double-notched test piece

For the Iosipescu 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 an asymmetric
four-point bending fixture. Failure of the test piece occurs by shear between the V-notches. Schematics of the
test setup and test piece are shown in Figures 3 and 4.

Figure 3 — Schematic of Iosipescu test piece subjected to asymmetric four-point bending loading
4 © ISO 2005 – All rights reserved

Dimensions in millimetres
Figure 4 — 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 test
piece fabrication may play an important role in the measured strength distributions and shall be reported.
6.3 Bending
Bending of uniaxially loaded shear test pieces (during the compression of double-notched test pieces) can
cause or promote non-uniform stress distributions that may alter the desired uniform state of stress during the
test.
6.4 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.
6.5 Notch separation
For the evaluation of the interlaminar shear strength by the compression of a double-notched test piece, the
distance between the notches has an effect on the maximum load and therefore on the interlaminar shear
strength. It has been found that the stress distribution in the test piece is independent of the distance between
the notches when the notches are far apart. However, when the distance between the notches is such that the
stress fields around the notches interact, the measured interlaminar shear strength increases. Because of the
complexity of the stress field around each notch and its dependence on the properties and homogeneity of the
material, it is recommended to perform a series of tests on test pieces with different spacing between the
notches, to determine their effect on the measured interlaminar shear strength.
6.6 Specimen clamping
Because the purpose of the jaws is to maintain the test piece in place and to prevent buckling, excessive
clamping force with the jaws of the fixture during the compression of double-notched test pieces will reduce
the stress concentration around the notches and therefore artificially increase the measured interlaminar
shear strength. In the case of the Iosipescu fixture, avoid over-tightening the jaws because it induces
undesirable pre-loading and may damage some materials.
6.7 Friction
Many fixtures for both the compression of double-notched test pieces and 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.
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.
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 digital data acquisition systems. Recording devices shall be accurate to within
± 1 % of the selected range for the testing equipment including readout unit, and have a minimum data
acquisition rate of 10 Hz with a response of 50 Hz deemed more than sufficient.
7.3 Dimension-measuring devices
Micrometers and other devices used for measuring linear dimensions shall be accurate and precise to at least
0,01 mm and shall be in accordance with ISO 3611. To obtain consistent measurements of test piece
dimensions, use a flat, anvil-type micrometer. Ball-tipped or sharp anvil micrometers are not recommended for
woven continuous-fibre-reinforced ceramic composites, because the resulting measurements may be affected
by the peaks and valleys of the weave. Measure test piece dimensions to within 0,02 mm.
6 © ISO 2005 – All rights reserved

7.4 Test fixtures
There are various types of fixtures for the compression of double-notched test pieces. One type consists of a
stationary element mounted on a base plate, an element that attaches to the cross-head of the testing
machine, and two jaws to fix the test piece in position. A schematic description of s
...