BS EN ISO 1421:2016 pdf download – Rubber- or plastics-coated fabrics — Determination of tensile strength and elongation at break
Principle A test piece is extended at a constant rate of extension until it breaks. For method 1 (clause 7), the maximum force and the elongation at maximum force and, if required, the force at break and the elongation at break are determined. For method 2 (clause 8), the maximum force only is determined.
5.1 Constant rate of extension (CRE) tensile testing machine, having the following general characteristics: The machine shall be provided with means for reading and recording both the force applied to the test piece in stretching it to the breaking point and the corresponding extension of the test piece. It shall be provided with a strength indicator having several scales in order to ensure that the rupture of each test piece is obtained with a strength of 15 % to 85 % of the maximum of the scale used. Under conditions of use, the accuracy of the apparatus shall be class 1 as defined in ISO 7500-1. The error of the indicated or recorded maximum force at any point in the range in which the machine is used shall not exceed ± 1 %, and the error of the indicated or recorded jaw separation shall not exceed 1 mm. After the first 2 s of the test, the rate of increase in the distance between the clamps shall be uniform to within 5 %. If the force and elongation are recorded by means of data acquisition boards and software, the frequency of data collection shall be at least 8 s –1 .
5.2 Clamping device, with the central point of the two jaws of the machine in the line of pull, the front edges at right angles to the line of pull and their clamping faces in the same plane. The jaws shall be capable of holding the test piece without allowing it to slip. They shall be designed so that they do not damage the test piece or reduce its strength. Smooth, flat or engraved corrugated jaws can be used for clamping. Using suitable packing materials in the jaws, e.g. paper, leather, plastics or rubber, avoids difficulties in clamping in many cases. When tests are carried out and the test pieces either break at the jaws or tend to slip, the results may often be discarded. In order to obtain legitimate results by avoiding jaw breaks and the effect of slippage, the use of capstan jaws or any other self-locking device can be a suitable alternative to ordinary flat jaws. When information on strain is required, elongation measurements are made by means of an extensometer which follows the movements of two reference points on the test piece. The use of such jaws and an extensometer shall be reported in the test report (see 7.4, item k). For the strip test method, the jaws shall be not less than the width of the test piece and should preferably have a width of at least 60 mm. For the grab test method, the dimensions of one of the jaws of each clamp shall be 25 mm ± 0,5 mm by 25 mm ± 0,5 mm. The other jaw of each clamp shall be at least as wide as the one to which it is attached and should preferably be 50 mm wide.
5.3 Equipment for cutting test pieces and fraying them down to the required width.
5.4 Equipment in which the test pieces can be immersed in water prior to wet testing.
5.5 Distilled or deionized water, for wetting out the test pieces.
5.6 Wetting agent or surfactant.
6 Atmosphere for conditioning and testing The atmosphere used for conditioning and testing shall be one of those specified in ISO 2231. The sample shall be conditioned for not less than 24 h. NOTE If the test results are to be representative of the properties of the coated fabric at the time of manufacturing and distribution, the tests must be carried out no longer than 3 months after the date of manufacture.
7 Method 1: strip test method
7.1 Sampling and preparation of test pieces From each sample, cut two sets of test pieces, one set in the longitudinal direction and the other in the transverse direction. Each set shall consist of not less than five test pieces. If, by agreement between the interested parties, a higher degree of precision is required, test more test pieces. Select the test pieces from the full usable width and length of the sample in accordance with ISO 2286-2. An example of how test pieces may be cut out is given in Figure 4. Each test piece shall be 50 mm ± 0,5 mm wide and of sufficient length to allow a distance of 200 mm ± 1 mm between the jaws of the test machine. If the elongation exceeds 75 %, reduce the length to 100 mm ± 1 mm.BS EN ISO 1421 pdf download.