Kevlar Properties Investigation Development of Kevlar Tensile Test Methods.

Testing procedures which are used for nylon parachute materials have not been satisfactory for testing their Kevlar counterparts. Kevlar's high strength and low elongation can result in premature breaks and, thus, inordinately low values of breaking strength. In an effort to understand the causes of these spuriously induced failures, a study was designed to investigate the reasons for premature breaks. Extensive tensile testing with a wide variety of Kevlar parachute component materials has led to the adoption of new jaws and testing techniques designed to give breaks in the free length with nearly simultaneous failure of all warp yarns, high values of breaking strength and low variability. The new jaws are described and their use illustrated for a range of typical parachute component materials. A set of design drawings for the optimized jaws is included, and a proposed text which describes the procedure to be used in tensile testing Kevlar narrow fabrics has been drafted for inclusion in Military Specifications. (Author)