ISO/TS 6857:2024

Technical
Specification
ISO/TS 6857
First edition
Fine ceramics (advanced ceramics,
2024-02
advanced technical ceramics) —
Physical properties of ceramic
composites — Guidelines for
determination of void and fibre
contents in polished cross section
by image analysis
Céramiques techniques (céramiques avancées, céramiques
techniques avancées) — Propriétés physiques des composites
céramiques — Lignes directrices pour la determination du taux
de porosité et de la teneur en fibre sur une section polie par
analyse d'images
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Significance and use . 2
6 Apparatus . 2
7 Test specimen . 2
7.1 Sampling .2
7.2 Mounting .3
7.3 Grinding and polishing .3
8 Procedures . 3
8.1 Calibration .3
8.2 Image acquisition .3
8.3 Void area content .3
8.3.1 Binarization .3
8.3.2 Pixel counting .4
8.3.3 Removal of smaller voids .4
8.4 Fibre area content by simplified method .4
8.4.1 Tow counting .4
8.4.2 Determination of mean filament area per tow .4
8.5 Fibre area content by detailed method .5
8.5.1 Filament detection .5
8.5.2 Pixel counting .6
9 Calculation . 6
9.1 Void area content .6
9.2 Fibre area content by simplified method .6
9.3 Fibre area content by detailed method .7
10 Report . 7
Bibliography . 8

iii
Foreword
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iv
Technical Specification ISO/TS 6857:2024(en)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Physical properties of ceramic composites —
Guidelines for determination of void and fibre contents in
polished cross section by image analysis
1 Scope
This document describes the methods for the determination of void and fibre with specific orientation
contents in a polished cross section of continuous fibre-reinforced ceramic matrix composites by image
analysis.
The methods apply to all ceramic matrix composites with continuous fibre reinforcement: bidirectional (2D)
and tridirectional (3D).
The methods also apply to carbon-fibre-reinforced carbon matrix composites (also known as: carbon/
carbon or C/C).
NOTE The result obtained by the method is not volume content but area content.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
fibre content
amount of fibre present in a cross section of composite
4 Principle
The test specimens are cut out of representative locations of samples or materials. The cutting sections of
test specimens are carefully polished and subjected to observation with an optical microscope or similar.
Digital images or photographs are taken at high magnification and analysed.
Voids are detected and discriminated based on the grayscale level differences compared to those of matrix
and fibres. The threshold value is determined from the histogram of the image. The image is binarized and
the void pixels are counted. The void area content is calculated as the ratio of the void pixels to the total
pixels.
There are two different determinati
...