Dynamic Properties of Filaments, Yarns, and Cords at Sonic Frequencies

Abstract

A brief description of the stretch-vibrometer developed at the Firestone Research Laboratories is given, and the theory of its operation is outlined. Described are new measurements made on the instrument verifying the previous conclusion that loss of energy to the apparatus is immeasur ably small. Values of the dynamic stretch moduli E, coefficients of internal friction μ, and hyster etic energy losses of 15 samples of natural and synthetic textile materials, Fiberglas, and steel wire are given. Corresponding static values of moduli and energy losses are also given. The latter, it is shown, do not correlate with dynamic values, and hence cannot be regarded as predictive of dynamic behavior. The resonant frequencies at which measurements were made on these samples ranged from 65 to 360 cycles per second. The significance of the various measures which have been employed with the present data to express hysteretic losses is discussed, and it is shown that the quantity μω 0/E, while not rigidly constant, is confined to a narrow range of values in most samples. Further evidence is submitted generalizing the near-hyperbolic relationship between μ and ωo. Results of application of the method to the comparison of various tire-cord rayons are given. Measured on the stretch-vibrom eter have been dynamic moduli ranging from 2.1 × 10 10 (rubber thread) to 226 × 1010 (steel wire) dynes/cm.2, and internal-friction coefficients from 0.74 × 106 (rubber thread) to 25.7 × 106 (silk thread) poises.