Fine ceramics (advanced ceramics, advanced technical ceramics) — Mechanical properties of ceramic composites at high temperature — Determination of stress-rupture time diagram under constant tensile loading

ISO 19604:2018 specifies the conditions for determination of the stress-rupture time diagram of continuous fibre-reinforced ceramic matrix composites (including carbon fibre-reinforced carbon matrix composite) at high temperature in air, vacuum and inert gas atmospheres under constant tensile loading. ISO 19604:2018 applies to all ceramic matrix composites with continuous fibre reinforcement: unidirectional (1D), bidirectional (2D) and tridirectional (xD, with 2 NOTE 1 In most cases, ceramic matrix composites to be used at high temperature in air are coated with an antioxidation coating. NOTE 2 Since the main purpose of the test is to obtain the stress-rupture time data, the deformation measurement is not mandatory.

Céramiques techniques (céramiques avancées, céramiques techniques avancées) — Propriétés mécaniques des composites à matrice céramique à température élevée — Détermination du diagramme contrainte temps de rupture sous chargement constant en traction

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Status
Published
Publication Date
24-Apr-2018
Technical Committee
Drafting Committee
Current Stage
9093 - International Standard confirmed
Start Date
07-Sep-2021
Completion Date
07-Sep-2021
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ISO 19604:2018 - Fine ceramics (advanced ceramics, advanced technical ceramics) -- Mechanical properties of ceramic composites at high temperature -- Determination of stress-rupture time diagram under constant tensile loading
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INTERNATIONAL ISO
STANDARD 19604
First edition
2018-05
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Mechanical properties of ceramic
composites at high temperature —
Determination of stress-rupture time
diagram under constant tensile loading
Céramiques techniques (céramiques avancées, céramiques techniques
avancées) — Propriétés mécaniques des composites à matrice
céramique à température élevée sous air et à pression atmosphérique
— Détermination du diagramme contrainte temps de rupture sous
chargement constant en traction
Reference number
ISO 19604:2018(E)
ISO 2018
---------------------- Page: 1 ----------------------
ISO 19604:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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Published in Switzerland
ii © ISO 2018 – All rights reserved
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ISO 19604:2018(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms, definitions and symbols ............................................................................................................................................................ 1

4 Principle ........................................................................................................................................................................................................................ 3

5 Significance and use .......................................................................................................................................................................................... 3

6 Apparatus ..................................................................................................................................................................................................................... 3

6.1 Test machine ............................................................................................................................................................................................. 3

6.2 Gripping devices .................................................................................................................................................................................... 4

6.2.1 General...................................................................................................................................................................................... 4

6.2.2 Active gripping devices .............................................................................................................................................. 4

6.2.3 Passive gripping devices ........................................................................................................................................... 4

6.3 Test chamber ............................................................................................................................................................................................ 4

6.4 Load indicator .......................................................................................................................................................................................... 4

6.5 Extensometer ........................................................................................................................................................................................... 6

6.5.1 General...................................................................................................................................................................................... 6

6.5.2 Mechanical extensometer ........................................................................................................................................ 7

6.5.3 Electronic optical extensometer ......................................................................................................................... 7

6.6 Heating apparatus ................................................................................................................................................................................ 7

6.7 Temperature measurement devices ..................................................................................................................................... 7

6.8 Data recording system ...................................................................................................................................................................... 8

6.9 Micrometers .............................................................................................................................................................................................. 8

7 Test specimens........................................................................................................................................................................................................ 8

7.1 Test specimen geometry ................................................................................................................................................................. 8

7.2 End tabs of specimen ......................................................................................................................................................................... 9

7.3 Test specimen preparation ........................................................................................................................................................10

7.4 Number of test specimens ..........................................................................................................................................................11

8 Test preparation ................................................................................................................................................................................................11

8.1 Alignment adjustment in tensile axis direction .......................................................................................................11

8.2 Adjustment of heating apparatus and temperature measuring device ..............................................11

8.3 Measurement of test specimen dimension ..................................................................................................................11

9 Test procedures ..................................................................................................................................................................................................12

9.1 Testing technique ...............................................................................................................................................................................12

9.1.1 Test specimen mounting ........................................................................................................................................12

9.1.2 Setting of extensometers .......................................................................................................................................12

9.1.3 Setting of inert atmosphere .................................................................................................................................12

9.1.4 Heating the test specimen ....................................................................................................................................12

9.1.5 Monitoring of temperature and elongation ...........................................................................................13

9.1.6 Applying load ...................................................................................................................................................................13

9.2 Post-testing treatment ...................................................................................................................................................................13

9.3 Test validity .............................................................................................................................................................................................13

9.4 Stress levels in tests .........................................................................................................................................................................14

9.5 Accidental interruption of the test ......................................................................................................................................14

10 Calculation of results ....................................................................................................................................................................................14

10.1 Tensile applied stress .....................................................................................................................................................................14

10.2 Tensile strain..........................................................................................................................................................................................15

10.3 Drawing of tensile strain curve ..............................................................................................................................................15

10.4 Drawing of stress-rupture diagram ...................................................................................................................................15

11 Test report ................................................................................................................................................................................................................15

© ISO 2018 – All rights reserved iii
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ISO 19604:2018(E)

Annex A (informative) Measurement procedure of bending ratio in the adjustment of a

tensile axis ...............................................................................................................................................................................................................17

iv © ISO 2018 – All rights reserved
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ISO 19604:2018(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.

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 documents 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).

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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

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World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
© ISO 2018 – All rights reserved v
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INTERNATIONAL STANDARD ISO 19604:2018(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Mechanical properties of ceramic composites
at high temperature — Determination of stress-rupture
time diagram under constant tensile loading
1 Scope

This document specifies the conditions for determination of the stress-rupture time diagram of

continuous fibre-reinforced ceramic matrix composites (including carbon fibre-reinforced carbon

matrix composite) at high temperature in air, vacuum and inert gas atmospheres under constant tensile

loading.

This document applies to all ceramic matrix composites with continuous fibre reinforcement:

unidirectional (1D), bidirectional (2D) and tridirectional (xD, with 2 < x ≤ 3), loaded along one principal

axis of reinforcement.

NOTE 1 In most cases, ceramic matrix composites to be used at high temperature in air are coated with an

antioxidation coating.

NOTE 2 Since the main purpose of the test is to obtain the stress-rupture time data, the deformation

measurement is not mandatory.
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 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment: Micrometers for

external measurements — Design and metrological characteristics

ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:

Tension/compression testing machines — Calibration and verification of the force-measuring system

ISO 17161, Fine ceramics (advanced ceramics, advanced technical ceramics) — Ceramic composites —

Determination of the degree of misalignment in uniaxial mechanical tests

ISO 20507, Fine ceramics (advanced ceramics, advanced technical ceramics) — Vocabulary

IEC 60584-1, Thermocouples — Part 1: Reference tables
IEC 60584-2, Thermocouples — Part 2: Tolerances
3 Terms, definitions and symbols

For the purposes of this document, the terms and definitions given in ISO 20507 and the following 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/
© ISO 2018 – All rights reserved 1
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ISO 19604:2018(E)
3.1
test temperature
temperature measured at the centre of the test specimen gauge section
3.2
calibrated length
part of the test specimen that has uniform and minimum cross-sectional area
3.3
gauge length

initial distance between reference points on the test specimen in the calibrated length

3.4
controlled temperature zone

part of the calibrated length (3.2) including the gauge length (3.3) where the temperature is within 20 °C

for the test temperature of <500 °C, and within 50 °C for the test temperature of ≥500 °C

3.5
initial cross-section area

total area of the cross-section of the test specimen within the calibrated length (3.2) at room temperature

3.6
apparent cross-section area
0 app

total area of the cross-section of the test specimen with an antioxidative protection

3.7
effective cross-section area
0 eff

total area corrected by a factor, to account for the presence of an antioxidative protection

3.8
applied tensile force
constant tensile force loaded to the test specimen
3.9
applied tensile stress

applied tensile force (3.8) supported by the test specimen at any time in the test divided by the initial

cross-section area
3.10
apparent tensile stress
app

applied tensile force supported by the test specimen at any time in the test divided by the apparent

cross-section area (3.6)
3.11
effective tensile stress
eff

applied tensile force (3.8) supported by the test specimen at any time in the test divided by the effective

cross-section area (3.7)
2 © ISO 2018 – All rights reserved
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ISO 19604:2018(E)
3.12
longitudinal deformation

increase in the gauge length (3.3) between reference points under a constant tensile force

3.13
tensile strain

relative change in the gauge length (3.3) defined as the ratio A/L under a constant tensile force

3.14
tensile strain rate
change in tensile strain per unit time under a constant tensile force
3.15
rupture time
time required for the test specimen to fracture under a constant tensile force
3.16
rupture strain
accumulated tensile strain to rupture under a constant tensile force
4 Principle

A constant uniaxial tensile force is applied to a test specimen of specified dimensions at high

temperature in ambient air, vacuum or inert gas atmospheres. By continuing the test until rupture or a

certain period, tensile strains and rupture time are determined.
5 Significance and use

Several mechanisms may be responsible for time-dependent deformation and rupture time of

continuous fibre-reinforced ceramic matrix composites at high temperature under a constant tensile

force. These may be creep of the fibre and/or the matrix, or may be caused by the composite nature

of the material (e.g. matrix micro-cracking, fibre-matrix interface sliding, oxidation-activated slow

crack growth, degradation of fibres). Creep behaviour is characterized by the total time-dependent

increase of the gauge length and the rupture time, starting from the time when the specified force level

is reached, whatever mechanism is responsible.
6 Apparatus
6.1 Test machine
The test machine shall conform to the following requirements.

a) The test machine shall meet the requirements of grade 1 or better of ISO 7500-1.

b) The forces loaded by the tensile testing machines shall be accurate to ±0,5 % at any force within

the force capacity range of 5 % to 100 %.

c) The test machine shall be installed so as not to be influenced by external vibration and shock.

d) The test machine shall be equipped with features to maintain alignment and transmit force to a

test specimen smoothly. A direct load or lever arm load test machine is desirable.

© ISO 2018 – All rights reserved 3
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ISO 19604:2018(E)
6.2 Gripping devices
6.2.1 General

Various types of gripping devices may be used to transmit the tensile force applied by the test machine

to the test specimen. The gripping design shall prevent the test specimen from slipping.

The gripping devices can be classified generally into two types. One is that employing an active grip

interface and the other is that employing a passive one.

In both types of grips, hot and cold grips can be used. The former is the grip where the gripping section

is in the hot zone of the furnace and the latter is the grip where the gripping section is outside of the

hot zone.

Such load train couplers as universal joints may be used to reduce the bending strains of test specimens.

NOTE The choice of gripping system depends on materials, test specimens and alignment requirements.

6.2.2 Active gripping devices

Active gripping devices transmit the tensile force from test machines to test specimens by a mechanical,

hydraulic or pneumatic force. An example of an active gripping device is shown in Figure 1.

The gripping surfaces shall be scored or serrated to prevent slippage between the gripping face and the

test specimen. Sufficient pressure shall be applied normal to the gripping face.
6.2.3 Passive gripping devices

Passive gripping devices transmit the tensile force from test machines to test specimens through

a direct mechanical link. Examples of the direct mechanical links are an edge loading type for a test

specimen with shank shoulders (see Figures 2 and 3) and a pin loading type for a test specimen with

pin-holes in gripping sections (see Figure 4).
6.3 Test chamber

For tests in a gas atmosphere or in a vacuum, a gastight chamber shall be used, which allows proper

control of the test environment in the vicinity of the test specimen during the test.

The installation shall be such that the variation of load due to the variation of pressure during the test

is less than 1 % of the scale of the load cell being used.

For tests in a gas atmosphere, the atmosphere shall be chosen depending on the material to be tested

and the test temperature. The level of pressure shall be determined depending on the material to be

tested, the temperature, the type of gas and the type of extensometer.

For tests in a vacuum, the degree of vacuum shall not induce chemical and/or physical instabilities of

the test material or the extensometer rods.
6.4 Load indicator

The load value shown by the load indicator shall be the same as that applied to the test specimen. There

are two methods of achieving this:
1. Method to install a load cell in a test chamber (direct method);

2. Method to calibrate chamber pressure and the indication value by the load cell initially installed

outside the chamber.

The load variation due to the pressure fluctuations in a chamber shall not exceed the limits

specified in 6.1.
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ISO 19604:2018(E)

The accuracy of alignment and load train of the test machine shall not be influenced by the heating.

Key
1 test specimen
2 wedge gripe
3 grip body
4 piston
Figure 1 — Example of an active gripping device
Key
1 grip attachment
2 test specimen
Figure 2 — Example of a passive gripping device
© ISO 2018 – All rights reserved 5
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ISO 19604:2018(E)
Key
1 pin
2 test specimen
Figure 3 — Example of a passive gripping device
Key
1 pin
2 test specimen
Figure 4 — Example of a passive gripping device
6.5 Extensometer
6.5.1 General

Any extensometers used shall be capable of continuous and stable recording of the longitudinal

deformation at test temperature for the entire testing duration. The linearity tolerances shall be lower

than 0,05 % of the extensometer range used. It is recommended that an extensometer with the greatest

gauge length possible is used.
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ISO 19604:2018(E)
Two commonly used types of extensometers are described in 6.5.2 and 6.5.3.
6.5.2 Mechanical extensometer

If a mechanical extensometer is used, the gauge length shall be the longitudinal distance between the

two locations where the extensometer rods contact the test specimen.

Structural changes in the rod material induced by temperature and/or environment shall not affect the

accuracy of deformation measurement. The rod material shall be compatible with the test specimen

material.

Care should be taken to correct for changes in calibration of the extensometer that may occur as a result

of operating under conditions different from calibration.

Rod pressure onto the test specimen should be the minimum necessary to prevent slipping of the

extensometer rods.
6.5.3 Electronic optical extensometer

If an optical extensometer with a laser beam, CCD camera or other devices is used, rods or flags attached

to the calibrated length as reference marks shall be mounted perpendicular to the test specimen axis.

The gauge length shall be the distance between the two reference marks. The rods or flags shall be

chosen to be compatible with the test material.

When using a test specimen integrated with flags, minimize stress concentration due to the flags.

6.6 Heating apparatus

Heating apparatus shall be equipped with a temperature control device that can heat the whole or part

of a test specimen at a constant rate of heating.

It shall provide a temperature control to keep the temperature distribution in the gauge length within

10 °C for the test temperature of <500 °C, and within 20 °C for the test temperature of ≥500 °C.

For the entire duration of the test, the heating apparatus shall be capable of controlling the testing

temperature within ±1 %.

For the adjustment of the heating apparatus and temperature measuring device, refer to 8.2.

6.7 Temperature measurement devices

Temperature measurements of heating apparatus and test specimens shall be made with thermocouples

or radiation thermometers that conform to IEC 60584-1 and IEC 60584-2.

In using radiation thermometers, measure in advance emissivity of the test specimen at the selected

wavelength. When temporal change in emissivity of the test specimen is remarkable, a monochromatic

radiation thermometer shall not be used.

When connecting a thermocouple to a test specimen to measure its temperature directly, do not use

a thermocouple that damages or causes a chemical reaction that has a detrimental effect on tensile

behaviour and strain measurement of the test specimen surface. Thermocouples shall be as insensitive

as possible to ageing. It is advisable to check at the end of the test if the thermocouple’s calibration still

conforms to the requirements.

NOTE In some cases, the variation of power injected into the heat system could be an indication of

thermocouple ageing.
© ISO 2018 – All rights reserved 7
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ISO 19604:2018(E)
6.8 Data recording system

Use a calibrated device to obtain an autographic record of applied load and gauge section elongation or

strain versus time. Either analogue chart recorders or digital data acquisition systems can be used for

this purpose. Recording devices shall be accurate to within 1,0 % of the selected range for the testing

system, including readout unit.
6.9 Micrometers

Micrometers used for the measurement of the dimensions of the test specimen shall conform to

ISO 3611.

NOTE A flat anvil-type micrometer is more suitable than a sharp anvil-type micrometer, because continuous

fibre-reinforced ceramic matrix composites in general have surfaces with microscopic irregularities.

7 Test specimens
7.1 Test specimen geometry

In this document, various types of test specimens in accordance with materials can be selected

depending on test purpose and testing machine. The geometry and dimensions of commonly used

dumbbell-type test specimens are shown in Table 1 and Figure 5. An example of the straight-type test

specimen is indicated in Table 2 and Figure 6. The test specimens given in ISO 14574 may also be used.

Regarding the surface finish of test specimens, either an as-fabricated or a machined test specimen may

be applicable according to the purpose of the test. The thickness of the test specimen shall be equivalent

to that containing more than three plies for 2D woven composites and more than two unit cells for 3D

woven composites.
Table 1 — Recommended dimensions for dumbbell-type test specimen
Item Dimension (mm) Tolerance (mm)
Total length, L ≥100 ±0,5
Calibrated length, L ≥30 ±0,2

Thickness, d ≥2 and a) three or more layers for simple woven composites or b) ±0,2

two or more structural unit cells for complex woven composites

Width in the calibrated ≥5 and a) three or more fibre bundle units for simple woven ±0,2

length, W composites or b) two or more structural unit cells for complex
woven composites
Width in the gripping sec- ≥10 and 1,4 W ±0,2
tion, W
Radius of fillet, R ≥10 ±2
Parallelism 0,05
8 © ISO 2018 – All rights reserved
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ISO 19604:2018(E)
Key
L calibrated length
L total length
W width in the calibrated length
W width in the gripping section
d thickness
R radius of fillet
Change cross-section smoothly from calibrated length to gripping section.
Connect calibrated length and gripping section with smooth surface.
Figure 5 — Typical dumbbell-type test specimen
Table 2 — Recommended dimensions for straight-type test specimen
Item Dimension (mm) Tolerance (mm)

Thickness, d ≥2 and a) three or more layers for simple woven composites or b) ±0,2

two or more structural unit cells for complex woven composites
Width, W ≥5 and a) three or more fibre bundle units for simple woven ±0,2
composites or two or more structural unit cells for complex
woven composites
Parallelism 0,05
Key
L total length
W width
d thickness
Figure 6 — Example of straight-type test specimen
7.2 End ta
...

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