Testing of High Strength Fabrics: Reporting Modulus, Low Strain Properties, and Ultimate Tensile Strength

Measurement of the tensile properties of high strength woven and knit fabrics, including geotextiles and geogrids traditionally make use of roller grip-type clamping systems. These grips are designed to allow a sample to be pulled in tension without applying an excessive crimping or compressive force on the specimen, thus avoiding premature failure. Roller grips, also known as capstan grips, also have the advantage of allowing the specimen to align itself with the applied force therefore loading the specimen uniformly across the width. However, since the specimen tightens itself around the grip during testing, crosshead travel cannot be used to measure specimen strain, which makes the determination of low strain properties and the selection of modulus values difficult. Two issues that must be addressed in obtaining low strain properties are how to measure sample strain and how to get an accurate and repeatable starting point for the test. This paper will explore alternate methods of gripping systems, strain measurement and data analysis with the objective of accurately measuring and reporting low strain properties of woven and knit textiles.