The most common tensile test used in the geotextile industry is the grab test as specified in ASTM D4632. The ASTM D4632 grab test method is a modification of a standard tensile test, for use with geotextile 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 geotextile materials, giving inaccurate tensile data and does not provide a correct measure of the bulk fabric material properties. The ASTM D4632 grab test eliminates edge effects by clamping the center of the sample width, away from the sample ends, and using 1 inch wide jaws on samples of 4 to 8 inch width.
Geotextile Grab Strength Test Standards
ISO 13934 Test Machines for Grab and Strip Tests of Fabric
ASTM D7004 Tensile Test of Reinforced Geomembranes
ASTM D4632 Grab Test For Geotextiles
In accordance with testing standards like ASTM D4632, data from geotextile 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. ASTM D4632 also gives specifications for testing wet geotextiles, which can provide data more accurately characterizing geotextile properties for the environments in which they will be used.
Most geotextile fabrics can be tested by ASTM D4632 but geotextiles 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. ASTM D6432 grab tests require special 25.4 mm x 50.8 mm (1 in x 2 in) front jaw faces, with opposing jaw faces at least as large. 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. Our tabletop tensile test machines (300 series) are a good fit for ASTM D4632 and textile tensile tests in general because they feature CRE (constant rate of extension or constant test speed) capabilities. They also meet and exceed ASTM D76 textile test machine standards.
Applicable Testing Standards
- ISO 13934 Test Machines for Grab and Strip Tests of Fabric
- ASTM D4632 Grab Test For Geotextiles
- ASTM D7004 Tensile Test of Reinforced Geomembranes
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Recommended Testing Accessories
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