National foreword

This Published Document is the UK implementation of ISO/TS 24858:2026.

The UK participation in its preparation was entrusted to Technical Committee PRI/0.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

This publication is not to be regarded as a British Standard.

Compliance with a Published Document cannot confer immunity from legal obligations.

This Published Document was published under the authority of the Standards Policy and Strategy Committee on 31 October 2026.

Foreword

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This document was prepared by Technical Committee ISO/TC 61, Plastics.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

As technologies for the commercialization of textile materials have advanced, the development of various functional materials based on fibres has increased. Conductive fibres are flexible and highly elastic materials with significant potential for application in next-generation electronic devices, and carbon fibres are also one of the conductive materials that exhibit electrical conductivity. The homogeneity of a conductive material is an important factor in determining the performance of the final product, and from a quality control perspective, it is necessary to have a method to analyse the distribution status of the raw material before it is processed. In the case of carbon fibres, a conductive material in the form of fibres, it is important to manage the arrangement of the fibres because the degree to which the filament strands are arranged can cause performance degradation in localized areas. Optical image analysis is a common method for checking the homogeneity of filaments in carbon fibres and can be used to analyse the arrangement of filaments on the surface, but it has limitations in analysing the presence and density of filaments arranged in the thickness direction. A method for continuously measuring the homogeneity of carbon fibres with large surface areas is eddy current measurement, which utilizes electrical conductivity properties. An eddy current measurement is used to detect discontinuities in materials that conduct electricity. This method is a reliable measurement that can identify materials with low electrical conductivity, such as spread carbon fibre tow, making it applicable to a wide range of industries. This document specifies a standard method for evaluating the homogeneity of a spread carbon fibre tow, a conductive fibre, using eddy current measurement.

Annex A gives the eddy current measurement data for impedance analysis based on the presence of defects.

1 Scope

This test method defines test terms and specifies a standard method for evaluating the homogeneity of electrically conductive spread carbon fibre tow using eddy current measurement. The impedance in the width direction of the fibre is measured continuously, and the standard deviation of the measured impedance determines the homogeneity of the conductive material in fibre form.

2 Normative references

3 Terms and definitions

4 Background — Impedance

5 Specimen

5.1 Sampling

5.2 Size

6 Apparatus

6.1 Probe

6.2 Sample stage

6.3 Gap

7 Test conditions

8 Procedure

9 Report of the results

9.1 General

9.2 Test environment

9.3 Test apparatus

9.4 Test conditions

9.5 Test results

Bibliography