Wide-width tensile test

EN ISO 10319 1996 Geotextiles - Wide-width Tensile Test or EN 29073-3 1992, Textiles - Test Methods for Nonwovens - Part 3 Determination of Tensile Strength and Elongation... 

ENISO 10319 1996 Geotextiles - Wide-width Tensile Test... 

For soil reinforcement, the prime role of the GTX is to provide structural integrity through its tensile behavior. Thus the load—extension characteristics of the GTX are of paramount importance to soil reinforcement apphcations. Three types of tests used to assess the tensile characteristics of GTX are the small-width tensile test (see Section 7.5.2), the grab test (see Section 7.5.1), and the wide-width tensile test (see Section 7.3.1). 

To achieve a practical test procedure for the wide-width tensile test, some considerations have to be given to the optimal GTX specimen width to be tested. Because... 

Table 7.2 Test conditions for wide-width tensile test on a geotextile...

Although the aim of the wide-width tensile test is to use as narrow a specimen width as is practicable (while maintaining plane strain conditions), when testing... 

The wide-width tensile test with 200 mm width and a 100-mm free length between clamps was specifically developed for GTX-N products with high lateral contraction, low strength, and high strain at rupture to obtain tensile values better related to field conditions than those determined in a strip tensile test. For other GTXs such as GTX-W with low strains, lateral contraction is negligible. 

Figure 7.1 Wide-width tensile test on a nonwoven geotextile using hydraulic clamps. Courtesy LGA.

The wide-width tensile test is used for design apphcations and QC applications. Tensile tests with higher test speeds and technically smaller representative widths can be used for QC instead if correlations for the standardized wide-width tensile tests are available. 

Figure 7.3 Wide-width tensile test on a knitted geotextile using capstan clamps. Courtesy SKZ.

Wide-width tensile tests provide a better measure of tme tensile strength than small-width tensile tests. The test data are presented in a load per unit width versus strain curve from which the modulus values (Eq. [7.1]) can be calculated. The specimens tested are not confined, as it would be in its end use this test does not result in a tme design value, especially for GTX-N. Nevertheless it is the index test for GTXs (Fig. 7.5). 

This tensile test is used as a control test for the evaluation of durability tests because of the small size of the specimens. The test result as maximum force of the exposed/ immersed specimens is only used relative to the maximum force of the control specimen. There is no simple relationship between small-width tensile tests of fabrics and wide-width tensile tests of GTXs (Table 7.7 and Fig. 7.9). 

Tensile tests on GTXs at low and elevated temperatures are not standardized. The wide-width tensile tests can be performed in an environmental chamber. The environmental chamber must be capable for a temperature control to an accuracy of 2°C of the indicated test temperature. The temperature must be controlled and recorded. The air temperature inside the chamber should be measured on the level of specimen being tested. The environmental chamber must have a size sufficient to perform the tensile tests with the appropriate clamps. The test temperature range of the environmental chamber should be at least between 60°C and +80°C. 

The future trend may not be to develop further index tests, but rather to make existing index tests more appropriate to the industry s needs. For example, the existing wide-width tensile tests are appropriate to GTX-W but not really for GTX-N because the testing speeds are too slow for QC tests and the strain measurements with exten-someter compared with grip separation measurements give similar results, and the use of an extensometer for highly extensible products like GTX-N is not really justified. 

Nowadays for design-related tests only the wide-width tensile test (WWTT) is used. The most common WWTTs are ASTM D4595 and ISO 10319, both of which use a 200-mm-wide specimen which is 100 mm long between the faces of the opposing grips. 

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