EN ISO 178:1996
(Main)Plastics - Determination of flexural properties (ISO 178:1993)
Plastics - Determination of flexural properties (ISO 178:1993)
Kunststoffe - Bestimmung der Biegeeigenschaften (ISO 178:1993)
1.1 Diese Internationale Norm legt ein Verfahren zur Ermittlung der Biegeeigenschaften von Kunststoffen unter definierten Bedingungen fest. Es ist ein genormter Probekörper festgelegt, jedoch sind die Parameter für andere Probekörpergrößen, falls angemessen, enthalten.
Plastiques - Détermination des propriétés en flexion (ISO 178:1993)
Polimerni materiali - Določanje upogibnih lastnosti (ISO 178:1993)
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Kunststoffe - Bestimmung der Biegeeigenschaften (ISO 178:1993)Plastiques - Détermination des propriétés en flexion (ISO 178:1993)Plastics - Determination of flexural properties (ISO 178:1993)83.080.01Polimerni materiali na splošnoPlastics in generalICS:Ta slovenski standard je istoveten z:EN ISO 178:1996SIST EN ISO 178:2000en01-maj-2000SIST EN ISO 178:2000SLOVENSKI
STANDARD
SIST EN ISO 178:2000
SIST EN ISO 178:2000
SIST EN ISO 178:2000
INTERNATIONAL STANDARD IS0 178 Third edition 1993-05-15 Plastics - Determination of flexural properties Plastiques - Dhermina tion des proprih t6s en flexion Reference number IS0 178:1993(E) SIST EN ISO 178:2000
IS0 178:1993(E) Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 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. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. 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. International Standard IS0 178 was prepared by Technical Committee ISO/lC 61, Plastics, Sub-Committee SC 2, Mechanical properties. This third edition cancels and replaces the second edition (IS0 178:1975), which has been improved in the following ways: - normative references have been added especially for specimen prep- aration and the use of multipurpose test specimens complying with IS0 3167; - a definition of modulus is given; - one strain rate only is recommended; - designation of quantities has been harmonized with those of other International Standards for testing plastics, in accordance with IS0 31. 0 IS0 1993 All rights reserved. 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 per- mission in writing from the publisher. International Organization for Standardization Case Postale 56 l CH-1211 Geneve 20 l Switzerland Printed in Switzerland ii SIST EN ISO 178:2000
INTERNATIONAL STANDARD IS0 178:1993(E) Plastics - Determination of flexural properties 1 Scope 1.1 This International Standard specifies a method for determining the flexural properties of plastics un- der defined conditions. A standard test specimen is defined, but parameters are included for alternative specimen sizes for use where appropriate. A range of testing speeds is included. 1.2 The method is used to investigate the flexural behaviour of the test specimens and for determining the flexural strength, flexural modulus and other as- pects of the flexural stress/strain relationship under the conditions defined. It applies to a freely supported beam, loaded at midspan (three-point loading test). 1.3 The method is suitable for use with the follow- ing range of materials: thermoplastics moulding and extrusion materials, including filled and reinforced compounds in addi- tion to unfilled types; rigid thermoplastics sheets; thermosetting moulding materials, including filled and reinforced compounds; thermosetting sheets, including laminates; fibre-reinforced thermoset and thermoplastics composites, incorporating unidirectional or non- unidirectional reinforcements such as mat, woven fabrics, woven rovings, chopped strands, combi- nation and hybrid reinforcements, rovings and milled fibres; sheets made from pre-impregnated materials (prepregs); thermotropic liquid-crystal polymers. The method is not normally suitable for use with rigid cellular materials and sandwich structures containing cellular material. NOTE 1 For certain types of textile-fibre-reinforced plas- tics, a four-point bending test is preferred. This is currently under consideration in ISO. 1.4 The method is performed using specimens which may be either moulded to the chosen dimen- sions, machined from the central portion of a standard multi-purpose test specimen (see IS0 3167) or ma- chined from finished and semi-finished products such as mouldings, laminates and extruded or cast sheet. 1.5 The method specifies preferred dimensions for the test specimen. Tests which are carried out on specimens of different dimensions, or on specimens which are prepared under different conditions, may produce results which are not comparable. Other fac- tors, such as the speed of testing and the conditioning of the specimens, can also influence the results. Consequently, when comparative data are required, these factors must be carefully controlled and re- corded. 1.6 Flexural properties can only be used for engi- neering design purposes for materials with linear stress/strain behaviour. For non-linear material behav- iour the flexural properties are only nominal. The bending test should preferentially be used with brittle materials, for which tensile tests are difficult. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publi- cation, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most re- cent editions of the standards indicated below. Members of IEC and IS0 maintain registers of cur- rently valid International Standards. IS0 291:1977, Plastics - Standard atmospheres for conditioning and testing. IS0 293: 1986, Plastics - Compression moulding test specimens of thermoplastic materials. SIST EN ISO 178:2000
IS0 178:1993(E) IS0 294:-‘1, Plastics - Injection moulding of test specimens of thermoplastic materials. IS0 295: 1991, Plastics - Compression moulding of test specimens of thermose tting materials. IS0 1209-I :I 990, Cellular plastics, rigid - Flexural tests - Part 1: Bending test. IS0 1209-2:1990, Cellular plastics, rigid - Flexural tests - Part 2: Determination of flexural properties. IS0 1268: 1974, Plastics - Preparation of glass fibre reinforced, resin bonded, low-pressure laminated p/a tes or panels for test purposes. IS0 2557-l : 1989, Plastics - Amorphous thermoplas- tics - Preparation of test specimens with a specified maximum reversion - Part 1: Bars. IS0 2557-2: 1986, Plastics - Amorphous thermoplas- tics - Preparation of test specimens with a specified reversion - Part 2: Plates. IS0 2602:1980, Statistical interpretation of test re- suits - Estimation of the mean - Confidence in ten/al. IS0 2818:+ Plastics - Preparation of test speci- mens by machining. IS0 3167: -3), P/as tics mens. - Multipurpose test speci- IS0 5893: 1985, Rubber and plastics test equipment - Tensile, flexural and compression types (constant rate of traverse) - Descrpuon. 3 Definitions Fo r the purposes of this fol lowing definitions apply. International Standard, the 3.1 speed of testing, V: Rate of relative movement between the supports and the striking edge, ex- pressed in millimetres per minute (mm/min). 3.2 flexural stress, of: Nominal stress of the outer surface of the test specimen at midspan. It is calculated according to the relationship given in 9.1, equation (3), and is expressed in megapascals (MPa). 3.3 flexural stress at break, afs: Flexural stress at break of the test specimen (see figure 1, curves a and b) . It is expressed in megapascals (MPa). 3.4 flexural strength, OfM: Maximum flexural stress sustained by the test specimen during a bending test (see figure 1, curves a and b). It is expressed in megapascals (MPa). 3.5 flexural stress at conventional deflection, gfC: Flexural stress at the conventional deflection sc ac- cording to 3.7 (see figure 1, curve c). It is expressed in megapascals (MPa). 3.6 deflection, s: Distance over which the top or bottom surface of the test specimen at midspan has deviated during flexure from its original position. It is expressed in millimetres (mm). 3.7 conventional deflection, sc: Deflection equal to I,5 times the thickness h of the test specimen. It is expressed in millimetres (mm). Using the span L = 16h, the conventional deflection corresponds to a flexural strain of 3,5 % (see 3.8). 3.8 flexural strain, gf: Nominal fractional change in length of an element of the outer surface of the test specimen at midspan. It is expressed as a dimensionless ratio or a percent- age (o/o). It is calculated according to the relationship given in 9.2, equation (4). 3.9 flexural strain at break, &fs: Flexural strain at break of the test specimen (see figure 1, curves a and b) . It is expressed as a dimensionless ratio or a percent- age (o/o). 3.10 flexural strain at flexural strength, &fM: Flexural strain at maximum flexural stress (see figure 1, curves a and b). It is expressed as a dimensionless ratio or a percent- age (%). 3.11 modulus of elasticity in flexure; flexural modulus, Ef: Ratio of the stress difference of2 - Of1 to the corresponding strain difference values (Ef 2 = 0,002 5) - (Ef, = 0,000 5) [see 9.2, equation (5)] . It is expressed in megapascals (MPa). 1) To be published. (Revision of IS0 294:1975) 2) To be published. (Revision of IS0 2818:1980) 3) To be published. (Revision of IS0 3167:1983) SIST EN ISO 178:2000
IS0 178:1993(E) NOTES 2 The flexural modulus is only an approximate value of Young’s modulus of elasticity. 3 With computer-aided equipment, the determination of the modulus & using two distinct stress/strain points can be replaced by a linear regression procedure applied on the part of the curve between these two points. 4 Principle The test specimen, supported as a beam, is deflected at constant rate at the midspan until the specimen fractures or until the deformation reaches some pre- determined value. During this procedure the force applied to the specimen is measured. 5 Apparatus 5.1 Testing machine 5.1.1 General The machine shall comply with IS0 5893 and the re- quirements given in 5.1.2 to 5.1.4, as follows. 51.2 Speed of testing The testing machine shall be capable of maintaining the speed of testing (see 3.1), as specified in table 1. S-------c sc = I,5 h I I I EfB EfM 4 B Ef - Curve a Specimen that breaks before yielding Curve b Specimen that shows a maximum and then breaks before the conventional deflection sc Curve c Specimen that neither has a yield point nor breaks before the conventional deflection sc Figure 1 - Typical curves of flexural stress of versus flexural strain Ef and deflection s SIST EN ISO 178:2000
IS0 178:1993(E) Table 1 - Recommended values for the speed of testing Speed Tolerance mm/min o/O 1 1) If 20 2) 2 * 20 2) 5 * 20 10 If: 20 20 * IO 50 * IO 100 St IO 200 f 10 500 f 10 I) The lowest speed is used for specimens with thicknesses between 1 mm and 3,5 mm, see 8.3. 2) The tolerances on the speeds 1 mm/min and 2 mm/min are lower than indicated in IS0 5893. 5.1.3 Supports and striking edge Two supports and a central striking edge are arranged according to figure2. The parallel alignment of the supports and the striking edge shall lie within + 0,02 mm. - The radius R, of the striking edge and the radius R, of the supports shall be as follows: R
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