Textile Grab Test Fixture Diagram

The most common tensile test used in the textile industry is called the grab test. The grab test method is a modification of a standard tensile test for use with woven and non woven textile fabrics that measures ultimate strength and elongation. A typical tensile test clamps the end of the specimen, which is effective when testing metals, plastics, and other traditional solid materials. However, this type of gripping introduces edge effects if used for textile materials, giving inaccurate tensile data and does not provide a correct measure of the bulk fabric material properties. The grab test eliminates edge effects by clamping the center of the sample width, away from the sample ends, and using jaws smaller than the sample width. As with all textile tests, alignment of the grip surfaces with the plane of the fabric sample is crucial for achieving accurate results. However, the orientation of the fabric in the sample is only significant if the material exhibits anisotropic material properties, which would give different strength values for off axis loading. Textile Grab Strength Test Standards In accordance with ASTM and ISO standards, data from grab test experiments is used to determine effective fabric strength, which is the fabric strength in a specific width together with the strength contributed by adjacent material. Popular grab test standards are ASTM D751 for coated fabrics, ASTM D1683 for woven apparel fabric seams, ASTM D2208 for soft, boarded, sueded, or embossed leather, ASTM D5034 for textile fabrics, and ISO 13934-2 for fabrics, and ISO 13935-2 for fabrics and made-up textiles, such as clothing apparel. Textiles tend to be difficult to test without slippage or jaw face breaks due to over- tightening. Pneumatic grips offer ease of use, productivity, and enhanced repeatability. Pneumatic action grips also allow the user to set clamp pressure. Common grab tests require special 25.4 mm x 50.8 mm (1 in x 2 in) front jaw faces, with the opposing jaw face at least as big. Grip pressure and specimen alignment are critical. Too much pressure produces premature breaks, and low pressure causes specimen slippage or breaks at or near the grip jaw faces. Slack correction is needed or the specimen is held too loosely in the grips at the start of the test. Tabletop tensile test machines are a good fit for textile tensile tests in general because they feature CRE (constant rate of extension or constant test speed) capabilities. They meet and exceed ASTM D76 textile test machine standards.

Applicable Testing Standards

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