3—THE EFFECT OF RATE OF EXTENSION ON THE TENSILE BEHAVIOUR OF VISCOSE AND ACETATE RAYONS, SILK AND NYLON

Abstract

The essential features of two instruments for recording the load–extension curves of yarns at constant rates of extension from 0·001 to 1000 per cent per second are described. They were used to investigate the effect of the rate of extension on the tensile behaviour of viscose rayon (continuous filament, and staple fibre), cellulose acetate rayon, silk and nylon at 65 per cent r.h. and 20°C. At any given extension, the stress is higher the higher the rate of extension and is approximately linearly related to the logarithm of the rate of extension for all the yarns except the cellulose acetate. The strength, and modulus of elasticity for the initial linear part of the specific stress versus strain curves, increase approximately linearly with the logarithm of the rate of extension. The breaking extension of the two viscose rayon yarns increases with rate of extension, although not linearly with the logarithm of the rate of extension, whilst that of cellulose acetate rayon is independent of the rate of extension. Breaking extension increases considerably with rate of extension for the silk yarn whereas the breaking extension of the nylon yarn shows a maximum value for a rate of extension of about 2 per cent per second.