ISO-17281-2002.pdf

Reference number ISO 17281:2002(E) © ISO 2002 INTERNATIONAL STANDARD ISO 17281 First edition 2002-11-01 Plastics Determination of fracture toughness (GIC and KIC) at moderately high loading rates (1 m/s) Plastiques Détermination de la ténacité à la rupture (GIC et KIC ) à vitesses de charge modérément élevées (1 m/s) Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/16/2007 10:19:41 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17281:2002(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. © ISO 2002 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.ch Web www.iso.ch Printed in Switzerland ii © ISO 2002 All rights reserved Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/16/2007 10:19:41 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17281:2002(E) © ISO 2002 All rights reserved iii Contents Page Foreword iv Introduction. v 1 Scope 1 2 Normative reference 1 3 Terms and definitions. 2 4 Test specimens . 2 4.1 Specimen geometry and preparation 2 4.2 Crack length and number of test replicates. 2 4.3 Measurement of test specimen dimensions. 2 5 Test conditions 2 5.1 Loading mode 2 5.2 Test speed 2 5.3 Test atmosphere and temperature 4 6 Test Equipment . 4 6.1 Loading machine. 4 6.2 Loading rigs. 4 6.3 Instrumentation . 4 7 Control of dynamic effects. 4 7.1 Electronic filtering. 4 7.2 Mechanical damping. 5 7.3 Damping level 5 7.4 Check on speed. 6 8 Data handling. 6 8.1 Analysis of the test records and identification of fracture initiation. 6 8.2 Energy correction 9 9 Expression of results 11 9.1 Determination of KIC. 11 9.2 Determination of y. 11 9.3 Determination of GIC. 12 10 Precision 13 11 Test report 15 Annex A (informative) Estimation of curve fit parameters . 16 Annex B (informative) Recommended test report forms 17 Bibliography 22 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/16/2007 10:19:41 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17281:2002(E) iv © ISO 2002 All rights reserved 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 3. 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 International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 17281 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 2, Mechanical properties. Annexes A and B of this International Standard are for information only. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/16/2007 10:19:41 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17281:2002(E) © ISO 2002 All rights reserved v Introduction This International Standard is based on a testing protocol developed by ESIS (the European Structural Integrity Society), Technical Committee 4, Polymers and Composites, who carried out the preliminary enabling research through a series of round-robin exercises which covered a range of material samples, specimen geometries, test instruments and operational conditions see 3-6. This activity involved about thirty laboratories from twelve countries. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/16/2007 10:19:41 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/16/2007 10:19:41 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD ISO 17281:2002(E) © ISO 2002 All rights reserved 1 Plastics Determination of fracture toughness (GIC and KIC) at moderately high loading rates (1 m/s) 1 Scope This International Standard provides guidelines for determining the fracture toughness of plastics in the crack- opening mode (Mode I) by a linear elastic fracture mechanics (LEMF) approach, at load-point displacement rates of up to 1 m/s. It supplements ISO 13586 so as to extend its applicability to loading rates somewhat higher than is the case in the scope of the latter International Standard. Fracture testing at high loading rates presents special problems because of the presence of dynamic effects: vibrations in the test system producing oscillations in the recorded quantities, and inertial loads producing forces on the test specimen different from the forces sensed by the test fixture. These effects need either to be controlled and, if possible, reduced by appropriate action, or else to be taken into account through proper analysis of the measured data. The relative importance of such effects increases with increasing testing rate (decreasing test duration). At speeds of less than 0,1 m/s (loading times of greater than 10 ms) the dynamic effects may be negligible and the testing procedure given in ISO 13586 can be applied as it stands. At speeds approaching 1 m/s (loading times of the order of 1 ms) the dynamic effects may become significant but still controllable. The procedure given in ISO 13586 can still be used though with some provisos and these are contemplated in this International Standard. At speeds of several meters per second and higher (loading times markedly shorter than 1 ms) the dynamic effects become dominant, and different approaches to fracture toughness determination are required, which are outside the scope of this International Standard. The general principles, methods and rules given in ISO 13586 for fracture testing at low loading rates remain valid and should be followed except where expressly stated otherwise in this International Standard. The methods are suitable for use with the same range of materials as covered by ISO 13586. Although the dynamic effects occurring at high loading rates are largely dependent on the material tested as well as on the test equipment and test geometry used, the guidelines given here are valid in general, irrespective of test equipment, test geometry and material tested. The same restrictions as to linearity of the load-displacement diagram, specimen size and notch tip sharpness apply as for ISO 13586. The linearity requirements referred to in 6.1 of ISO 13586:2000, are verified here on the “smoothed” load- displacement curve, to be obtained as specified in 8.1. 2 Normative reference The following normative document contains provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 13586:2000, Plastics Determination of fracture toughness (GIC and KIC ) Linear elastic fracture mechanics (LEFM) approach Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/16/2007 10:19:41 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17281:2002(E) 2 © ISO 2002 All rights reserved 3 Terms and definitions For the purposes of this International Standard, the terms and definitions given in ISO 13586 apply. 4 Test specimens 4.1 Specimen geometry and preparation As for the low-rate testing case covered by ISO 13586, two test configurations are recommended, namely the three-point bending (also called single edge notch bend and denoted SENB) and the compact tension (denoted CT), see Figure 1. Shape and size, preparation, notching and conditioning of test specimens shall comply with the requirements set out in clause 4 of ISO 13586:2000. 4.2 Crack length and number of test replicates 4.2.1 Determination of KIC As in the low-rate testing case covered by ISO 13586, measuring test specimens having the same crack length is adequate for determining KIC. The initial crack length a should be in the range 0,45 u a / w u 0,55. However, in view of the lower degree of accuracy to be expected with measurements at high rates of loading as compared with low- rate testing, it is recommended that at least five replicates, with crack lengths in the range specified above, be used to determine KIC, and the results averaged. 4.2.2 Determination of GIC At variance with the low-rate testing case covered by ISO 13586, a multispecimen procedure, using a series of test specimens with identical dimensions but varying crack-length as specified below, shall be applied for determining GIC. At least fifteen valid determinations shall be made, with initial crack length varying over the range 0,20 u a / w u 0,70 for the SENB configuration and 0,40 u a / w u 0,75 for the CT configuration. They may include the five determinations made on test specimens having initial crack lengths in the range 0,45 u a / w u 0,55 to obtain KIC. It is then suggested that, of the remaining ten test specimens to be used, six have initial crack lengths in the range 0,20 u a / w u 0,45 and four in the range 0,55 u a / w u 0,70 in the case of the SENB configuration and three have initial crack length in the range 0,40 u a / w u 0,45 and seven in the range 0,55 u a / w u 0,70 in the case of the CT configuration. 4.3 Measurement of test specimen dimensions Measurement is carried out as described in 5.6 of ISO 13586:2000. 5 Test conditions 5.1 Loading mode The test shall be performed at constant load-point displacement rate. A maximum variation of 10 % in the load- point displacement rate during the test is allowed (see 6.1). 5.2 Test speed As a basic test condition, it is recommended that a load-point displacement rate of 1 m/s be used. If a different rate is applied, it shall be quoted in the test report. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/16/2007 10:19:41 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17281:2002(E) © ISO 2002 All rights reserved 3 a) SENB b) CT Figure 1 Test configurations as specified in 4.1 and 6.2 With rate-sensitive materials such as plastics, a more significant measure of the rate of the experiment is probably its duration, i.e. the time required to bring the test specimen to fracture. The time to fracture, tf, is understood here as the time interval between the moment when the load starts acting on the test specimen and the point of fracture initiation as defined in 8.1. With a fixed load-point displacement rate the time to fracture varies with material and specimen geometry. If results at a given time to fracture (e.g. 1 ms) are desired, it is necessary to adapt the load-point displacement rate of the test to each material and specimen geometry (type and dimensions). For this purpose it is expedient to run some preliminary trial tests at different testing speeds (i.e. load-point displacement rates) to determine the testing speed required to obtain the assigned time to fracture under the given test conditions. In any case, the time to fracture, tf, shall also be quoted in the test report. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Aramco HQ/9980755100 Not for Resale, 04/16/2007 10:19:41 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17281:2002(E) 4 © ISO 2002 All rights reserved 5.3 Test atmosphere and temperature These are determined as described in 5.5 and 5.7 of ISO 13586:2000. 6 Test equipment 6.1 Loading machine Any type of loading machine (impact pendulums, falling-weight towers, servohydraulic universal testing machines, etc.) is permitted, prov