1、 Reference number ISO 17281:2002(E) ISO 2002INTERNATIONAL STANDARD ISO 17281 First edition 2002-11-01 Plastics Determination of fracture toughness (G ICand K IC ) at moderately high loading rates (1 m/s) Plastiques Dtermination de la tnacit la rupture (G ICet K IC ) vitesses de charge modrment leves
2、 (1 m/s) ISO 17281:2002(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes 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.
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5、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
6、ISOs 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 reservedISO 17281:2002(E) ISO 2002 All rights reserved iiiContents
7、 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 Tes
8、t 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 t
9、he test records and identification of fracture initiation . 6 8.2 Energy correction 9 9 Expression of results 11 9.1 Determination of K IC . 11 9.2 Determination of y . 11 9.3 Determination of G IC . 12 10 Precision 13 11 Test report 15 Annex A (informative) Estimation of curve fit parameters . 16 A
10、nnex B (informative) Recommended test report forms 17 Bibliography 22 ISO 17281:2002(E) iv ISO 2002 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Sta
11、ndards 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
12、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
13、 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 possibi
14、lity 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 a
15、nd B of this International Standard are for information only. ISO 17281:2002(E) ISO 2002 All rights reserved vIntroduction This International Standard is based on a testing protocol developed by ESIS (the European Structural Integrity Society), Technical Committee 4, Polymers and Composites, who car
16、ried 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. INTERNATIONAL STANDARD ISO
17、 17281:2002(E) ISO 2002 All rights reserved 1Plastics Determination of fracture toughness (G ICand K IC ) 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 linea
18、r 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 presen
19、ts 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 a
20、nd, 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 m
21、s) 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 th
22、ough 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 ou
23、tside 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
24、 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 ge
25、ometry 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 obtai
26、ned 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. Ho
27、wever, 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
28、IEC maintain registers of currently valid International Standards. ISO 13586:2000, Plastics Determination of fracture toughness (G ICand K IC ) Linear elastic fracture mechanics (LEFM) approach ISO 17281:2002(E) 2 ISO 2002 All rights reserved3 Terms and definitions For the purposes of this Internati
29、onal 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 SEN
30、B) 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 K ICAs in the low-rate testi
31、ng case covered by ISO 13586, measuring test specimens having the same crack length is adequate for determining K IC . 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
32、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 K IC , and the results averaged. 4.2.2 Determination of G ICAt variance with the low-rate testing case covered by ISO 13586, a multispecimen procedu
33、re, using a series of test specimens with identical dimensions but varying crack-length as specified below, shall be applied for determining G IC . 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
34、 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 K IC . It is then suggested that, of the remaining ten test specimens to be used, six have initial crack lengths in t
35、he 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 dimension
36、s 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 basi
37、c 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. ISO 17281:2002(E) ISO 2002 All rights reserved 3a) SENB b) CT Figure 1 Test configurations as specified in 4.1 and 6.2 With rate-sensitive
38、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, t f , is understood here as the time interval between the moment when the load starts acting on the test
39、 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 th
40、e 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 t
41、est conditions. In any case, the time to fracture, t f , shall also be quoted in the test report. ISO 17281:2002(E) 4 ISO 2002 All rights reserved5.3 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 l
42、oading machine (impact pendulums, falling-weight towers, servohydraulic universal testing machines, etc.) is permitted, provided it is capable of applying an adequate load to bring the test piece to fracture at the required load-point displacement rate and of maintaining this rate constant throughou
43、t the test up to fracture initiation. With testing machines of limited capacity, this requirement may need to be verified by preliminary tests, especially when new materials are tested or when new test conditions (e.g. change in specimen size) are used. Any variation in the load-point displacement r
44、ate during the test shall be determined and quoted if it exceeds 10 % of the rate at fracture initiation. 6.2 Loading rigs Unlike for low-rate testing, the use of fixed anvils rather than moving rollers is preferred for conducting three-point bend (SENB) fracture tests under high rate conditions, as
45、 is normally the case with standard impact pendulums. The span between the supports shall be adjustable however, so that specimens of different size can be accommodated, as specified in clause 4 of ISO 13586:2000. NOTE In the case of three-point bend testing (SENB specimens), improved results can be
46、 obtained if the testpiece is held in contact with the anvils by light springs (e.g. rubber bands). These will assist in maintaining the testpiece in position during the sudden load transmission from the machine to the test specimen, and ensure more reproducible records. 6.3 Instrumentation Acquisit
47、ion of a complete record of the load/time response of the material sample under test is essential for the determination of K IC . In addition, a means of evaluating the displacement of the moving load-point during the test is necessary for the independent determination of G IC . Instrumentation of t
48、he testing machine should thus comprise, basically, a force sensing and recording system and a displacement measuring and recording system or devices to measure and record quantities from which the load and the load-point displacement can also be indirectly determined. The adequacy of the response o
49、f this equipment to the dynamic events occurring in the relevant determinations shall be checked. It can be considered satisfactory if a plain plastic specimen (without any mechanical damping device in place) shows an inertial peak (see Figure 2) larger than 100 N at 1 m/s test speed. The response time shall be 20 % of the input signal rise time. If a digital recording system is used, the sampling time should be less than 1/200 of the time to fracture, i.e. at least 200 data points should be collected over the time interval fr
