Fatigue in Textile Fibers1

Abstract

Specimens of a polyester fiber (Dacron³ 52), with zero twist and 100 turns per inch have been fatigued in cyclic tension, with a few different static (bias) loads. In two experiments an intermediate twist was used. 'With low loads it was found that the lifetime generally increases with twist. This effect is reversed when the specimens are subjected to greater static loads, presumably reflecting a tightening of the molecular, or microfibrillar structure. Average lifetime, in both untwisted and twisted fibers, was found to decrease drastically with increases in the static load. With a low static load a smaller amount of creep occurs in twisted fibers during a fatigue test than in untwisted controls. When the load is increased, it was found that this tendency is reversed.