ISO 20505:2005

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

ISO 20505:2005 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.

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

General Information

• Status: Published
• Publication Date: 20-Sep-2005
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: ISO/TC 206 - Fine ceramics
• Drafting Committee: ISO/TC 206/WG 4 - Composites
• Current Stage: 9092 - International Standard to be revised
• Completion Date: 20-Nov-2020

Standards Content (Sample)

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 20505:2005(E)
ISO 2005
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ISO 20505:2005(E)
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ii © ISO 2005 – All rights reserved
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ISO 20505:2005(E)
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

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ISO 20505:2005(E)

13 Test report............................................................................................................................................ 16

Annex A (informative) Results of round-robin tests ..................................................................................... 18

Bibliography ..................................................................................................................................................... 20

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ISO 20505:2005(E)
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.
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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
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ISO 20505:2005(E)
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
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
Maximum load N Equations 1, 3
max
Shear area for double-notched test piece Equations 1, 2
Shear area for Iosipescu test piece mm Equations 3, 4
Interlaminar shear strength MPa Equations 1, 3
Mean value MPa Equations 5, 6, 7
SD Standard deviation MPa Equations 6, 7
CV Coefficient of variation 1 Equation 8
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ISO 20505:2005(E)
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

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ISO 20505:2005(E)
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

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ISO 20505:2005(E)
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.
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ISO 20505:2005(E)
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.

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ISO 20505:2005(E)
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 such a test fixture is shown

in Figure 5. Another type is a simple anti-buckling test fixture, where the test piece is held in position using a

plate that clamps the test piece against a stationary element mounted on a base plate. Figure 6 shows a

schematic of such a fixture. For the Iosipescu test, a modified asymmetric four-point bending fixture is

recommended. This fixture consists of a stationary element mounted on a base plate, and a movable element

capable of vertical translation guided by a stiff post. The movable element is attached to the cross-head of the

testing machine. Each element clamps half of the test piece into position, with a wedge-action grip that is able

to compensate for minor variations in test piece width. A span of 13 mm is left unsupported between fixture

halves. An alignment tool is recommended to ensure that the test piece notch is aligned with the line-of-action

of the loading fixture. Figure 7 shows a photograph of a commercially available Iosipescu fixture, while

Figure 8 shows a schematic of it.

Figure 5 — Example of anti-buckling fixture for compression of double-notched test piece

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ISO 20505:2005(E)

Figure 6 — Example of anti-buckling fixture for compression of double-notched test piece

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ISO 20505:2005(E)

The test pieces in the foreground illustrate the use of adhesively bonded end-tabs for evaluating specimens

obtained from thin plates.
Figure 7 — Photograph of commercially available fixture for Iosipescu test
Key
1 adjustable wedge to tighten the specimen 5 fixture guide rod
2 stationary portion of fixture 6 wedge-adjusting screw
3 load 7 fixture attached to guide rod by linear rolling bearing
4 specimen
Figure 8 — Schematic of Iosipescu test fixture
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ISO 20505:2005(E)
8 Test piece
8.1 Test piece geometry
8.1.1 Double-notched test piece

Double-notched test pieces shall conform to the shape and tolerances shown in Figure 2. The double-notched

test piece consists of a rectangular plate with notches machined on both sides. The depth of the notches shall

be at least equal to one-half of the test piece thickness, and the distance between the notches shall be

determined considering the requirements to produce shear failure in the gauge section. Furthermore, because

the measured interlaminar shear strength may be dependent on the notch separation, it is recommended to

perform tests with different values of notch separation to determine this dependence. The edges of the test

pieces shall be smooth, but not rounded or bevelled. Table 2 contains recommended values for the

dimensions associated with the test piece shown in Figure 2.
Table 2 — Recommended dimensions for double-notched compression test pieces
Values in millimetres
Dimension Description Value Allowance
Test piece length 30,00 ± 0,1
h Distance between notches 6,00
± 0,1
w Test piece width 15,00 ± 0,1
d Notch width 0,50 ± 0,05
t/2
Notch depth + 0,01/- 0,0
t Test piece thickness —
8.1.2 Iosipescu test piece

The required shape and tolerances of the Iosipescu test piece are shown in Figure 4, while Table 3 contains

recommended values for the dimensions of the test piece. If required, the dimensions of the test piece,

particularly the notch angle, notch depth and notch radius, may be adjusted to meet special material

requirements, but any deviation from the recommended values listed in Table 3 shall be reported with the test

results, although the standard tolerances shown in Figure 4 still apply.

Because, in some instances due to limitations in material processing, it may be difficult to produce thick

sections to conform with the dimensions and geometry shown in Table 3 and Figure 4, respectively, the test

piece geometry may be modified to obtain appropriate results. In this case, adhesively bonded end-tabs may

be used, and the depth and angle of the notches shall be selected to promote shear failure between the

V-notches. Figure 9 shows an example of this situation (such a specimen is shown in the foreground in

Figure 7).
Table 3 — Recommended dimensions for Iosipescu test pieces
Dimension Description Value Allowance
L Test piece length 76,00 mm
± 0,1
h Distance between notches 11,00 mm
± 0,1
w Test piece width 19,00 mm ± 0,1
Notch radius 0,50 mm
Θ Notch angle 90°
Test piece thickness —
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ISO 20505:2005(E)
Key
1 specimen
2 adhesively bonded end-tab
Figure 9 — Schematic of short losipescu test piece
8.2 Test piece preparation
8.2.1 Customary practices

In instances where a customary machining procedure has been developed that is completely satisfactory for a

class of materials (that is, it induces no unwanted surface/subsurface damage or residual stresses), this

procedure shall be used.
8.2.2 Standard procedures

Studies to evaluate the machinability of continuous-fibre reinforced ceramic composites have not been

completed. Therefore, the standard procedures of this subclause can be viewed as starting-point guidelines,

but a more stringent procedure may be necessary.

All grinding or cutting shall be done with an ample supply of appropriate filtered coolant, to keep the workplace

and grinding wheel constantly flooded and particles flushed. Grinding can be done in at least two stages,

ranging from coarse to fine rate of material removal.

The stock removal rate shall be on the order of 0,03 mm per pass, using diamond tools that have between

320 and 600 grit. Remove equal amounts of stock from each face where applicable.
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ISO 20505:2005(E)
8.2.3 Handling precautions

Exercise care in the storing and handling of finished test pieces to avoid the introduction of severe flaws. In

addition, direct attention to pre-test storage of test pieces in controlled environments or desiccators, to avoid

unquantifiable environmental degradation of test pieces prior to testing.
8.3 Number of test pieces

A minimum of 5 valid test results is required for the purpose of estimating a mean value. A greater number of

tests may be necessary, if estimates regarding the form of the strength distribution are required.

9 Precautionary statement

During the conduct of this test method, the possibility of flying fragments of broken test material may be high.

The brittle nature of advanced ceramics and the release of strain energy contribute to the potential release of

uncontrolled fragments upon fracture. Means for containment and retention of these fragments for later

fractographic reconstruction and analysis is highly recommended.

WARNING — Exposed fibres at the edges of continuous-fibre-reinforced ceramic composite test

pieces present a hazard due to the sharpness and brittleness of the ceramic fibres. All persons

required to handle these materials must be well informed of these conditions and the proper

...