Cumulative Geometric Changes in Woven Fabrics with Repeated Flexing'

Abstract

Extreme structural reorganization sometimes results from repeated flexing of fabrics that are tightly woven from multifilament yarns. This phenomenon has been inves tigated experimentally using a series of specially designed, narrow woven fabrics that were repeatedly cycled in bending under controlled laboratory conditions. The effects of yarn twist and yarn spacing on the extent of this reorganization, called "napping," have been studied. A simple model previously developed for bent waveforms is used to illustrate the mechanism of raised loop formation. Experimental results from the controlled flexing of a variety of fabric constructions suggest that a close match between yarn twist periodicity and weave periodicity is a necessary but not sufficient condition for nap formation in tightly woven, scoured fabrics; the distance between restrictions imposed by crossing yarns must also lie between certain limits for the phenomenon to occur to any marked extent.