ISO INTERNATIONAL 178 STANDARD Sixth edition 2019-04 Plastics Determination of flexural properties Plastiques - Détermination des propriétés en flexion Reference number IS0 178:2019(E) ISO 4 @ IS0 2019 IS0 178:2019(E) COPYRIGHT PROTECTED DOCUMENT IS0 2019 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either IsO at the address below or Iso's member body in the country of the requester. ISO copyright office CP 401 : Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +41 22 749 01 11 Fax: +41 22 749 09 47 Email: [email protected] Website: www.iso.org Published in Switzerland i @ IS0 2019 - All rights reserved IS0 178:2019(E) Contents Page Foreword ..iv 1 Scope .1 2 Normative references .1 3 Terms, definitions and symbols 4 Principle ..5 5 Test machine .5 5.1 General .5 5.2 Test speed .6 5.3 Supports and loading edge. 6 5.4 Force- and deflection-measuring systems .6 5.4.1 Introductory remarks. 6 5.4.2 Definition of precision and accuracy requirements .6 5.4.3 Deflection measurement ..8 5.5 Equipment for measuring the width and thickness of the test specimens .9 Test specimens. .9 6 Shape and dimensions .9 6.1 6.1.1 .9 General. Preferred specimen type 6.1.2 .9 Other test specimens. 6.1.3 .10 6.2 .10 Anisotropic materials 6.3 Preparation of test specimens. ..11 6.3.1 From moulding, extrusion and casting compounds 11 6.3.2 From sheets 11 6.4 Specimen inspection .11 6.5 Number of test specimens .12 7 Atmosphere for conditioning and testing ..12 8 .12 Procedure 9 Calculation and expression of results ..16 9.1 Flexural stress.. .16 9.2 Flexural strain .16 9.3 Flexural modulus. 16 9.4 Statistical parameters 17 9.5 Significant figures .17 10 Precision .17 Test report. 11 ..17 Annex A (informative) Precision statement. ..19 Annex B (informative) Influence of changes in test speed on the measured values of ..21 flexural properties. Annex C (normative) Compliance correction for Type III-tests ..22 Annex D (informative) Relation between tensile and flexural modulus: Theoretical expectations and experimental observations .24 Bibliography .25 iii @ IS0 2019 - All rights reserved IS0 178:2019(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 n