Mechanical Behavior of Nylon Filaments in Torsion

Abstract

The stress relaxation in torsion of 6,6-nylon filament is found to be nearly linear in the logarithm of time over periods from 20 to 20,000 sec. after twisting. On the basis of a generalized Maxwell model the behavior of the filament in free torsional vibration can be predicted from the results of the stress-relaxation experiments. The predictions were tested by experiments with a torsional pendulum whose period was varied from 50 to 400 sec. The angular displacement of the pendu lum is an exponentially damped sinusoid over nearly the entire course of the motion. The ob served dependence of the angular frequency upon the moment of inertia of the bob and the length of the filament agrees within 3 % with the values predicted from the stress-relaxation experiments. The observed and predicted values of the damping constant agree within 13%. The stress relaxa tion in extension also is found to be nearly linear in the logarithm of time over periods from 10 to 2,000 sec. after stretching. Quantitative correlation between torsional properties and extensional properties has not been made because of the complications introduced by the anisotropy of the drawn nylon.