Effect of gage length and test speed on the measured tensile properties of geosynthetic reinforcements

This research will specifically address the tensile testing of textile products employing high tenacity industrial quality multifilament twill textile yarns. The research reported in this paper is directed toward developing a repeatable and reproducible test method for textile reinforcements. The paper will present a new testing technique, which uses pressure clamping system as opposed to conventional roller grip systems. The pressure clamping system incorporates a technique used in other disciplines for very strong materials. This technique is the application of sacrificial tabs to the clamping area of the specimen, thus permitting very high jaw pressures without specimen damage. The specific concerns about testing of reinforcing products expressed in the literature are: (1) the effect of sample gage (length) on reported values including tensile strength, extension and modulus, (2) the effect of test speed, i.e. strain rate on reported values: one specific issue is the difference between ASTM at 10% and ISO at 20% per minute, (3) the effect of jaw or grip types on reported values, (4) the control of sample slippage in grips, (5) the amount of tolerable slippage in clamping devices, (6) the accuracy of various extension measurement systems, (7) the effect of the extension measurement system on the reported values, (8) the effect of sample width on reported values, (9) the definition, measurement and reporting of modulus, (10) which modulus is important and (1 1) what portion of the sample does a reported modulus represent. The paper will focus on four of the concerns. The issues addressed are sample length and sample gage (area of extension measurement), method of extension measurement, test speed and modulus measurements.