Abstract
To obtain maximum yarn strength translational efficiency in Kevlar 29 parachute webbings, the pick frequency must be reduced to the extent that the structure is too loose to be useable. As a result only modest efficicncy has been achieved in Kevlar 29 webbings. It has been shown that only part of the strength decrease is caused by the weaving process; hence, warp and fill yarn interaction during loading contribute to the loss in efficiency.
A test fixture was developed to measure the strength of a yarn sample threaded through a series of wires or yarns. This enabled the effect of warp twist and ply on warp strength to be easily and quickly determined under simulated crimp conditions. It was found that yarn strength decreases with decreasing pick spacing in the fixture, as is observed in woven fabrics, and the magnitude of strength decrease varies with yarn twist. optimum fabric strength was predicted to occur at lower warp-twist levels than those established using conventional yarn tests. Comparisons were made between the simulation results and the limited data available for woven structures. A general correlation was obtained for cases where the warp yarns were compressed during fabric construction.
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