Abstract
The viscoelastic properties of some commercial textile fibers were measured by means of several longitudinal-vibration methods over a range of frequency from 2 X 10-1 to 2 X 105 cps at 20°C, 65% R.H., under a static tension of 0.4 g/den and a dynamic strain of less than 0.1%.
In the above experiments, the nonlinear characteristics of vibrational properties were negligibly small, and the experimental results were described by the complex dy namic modulus function E*(ω) on the assumption that the Boltzmann superposition principle was valid.
Generally speaking, for all the textile fibers tested the real part of the complex dy namic modulus was found to be flat over this frequency range except there was some increase in the supersonic range. The imaginary part of the complex dynamic modulus, on the other hand, seemed to increase at both ends of the frequency range covered.
It was concluded from our experimental results that for any textile fiber there is not so anomalous a dispersion as that of various rubberlike materials found in the same frequency range.
Furthermore, according to the method of representation by a continuous distribution of relaxation times, the shape of the so-called "relaxation spectrum" of any textile fiber was found to be fairly flat over the relaxation-time range from 1 X 10-6 to 1 X 10° sec. With the exception of slight increases at both ends of this relaxation-time range the spectrum can be represented by the so-called "box distribution." This is very differ ent from the spectra of rubberlike materials over the same relaxation-time range.
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