Wave Propagation and Dynamic Modulus in Continuous-Filament Twisted Yarns1

Abstract

An analytical and experimental study of dynamic modulus in continuous-filament twisted yarns is performed to establish how small amplitude strain waves are propagated in this type of assembly and to determine if the dynamic and static moduli, as affected by geometric twist, are related. The dynamic modul us of nylon, dacron, viscose, and acetate yarns are measured as a function of twist angle at low stress levels, using the sonic velocity pulse-propagation technique. Excellent agreement between measured and predicted results indicate that, under these test conditions, strain waves propagate as longitudinal plane waves in a linear elastic medium, and the reduction in dynamic modulus with twist is principally a geometric effect which can be predicted by using the static extension theory.