Dynamic mechanical behavior of a composite viscoelastic material

Abstract

This paper is concerned with a study on the dynamic mechanical behavior of1a rubberlike material (Solithane 113) filled with finely divided aluminium spherical particles of prescribed volume concentrations at frequencies in the lower audiofrequency range, and at several temperatures above and below room temperature. The dynamic behavior of the material is studied by subjecting a specimen in the form of a rod to longitudinal vibrations and determining the resonant frequencies and the band-widths of the mechanical resonance curve, corresponding to various modes of vibration. From the dynamic mechanical data obtained at several temperatures and frequencies, reduced curves for the storage and loss modulus corresponding to a standard temperature are constructed for an extended frequency range by utilizing the time-temp. shift hypothesis. An examination of the dynamic data for various filler concentrations indicates that the viscoelastic transition region is shifted to lower frequencies with the increase in the volume fraction of the filler in the bulk material. For frequencies beyond 150 cycles, the storage and the loss modulus increase with the increase in the volume fraction of the filler. The rate of increase in the modulus functions being larger at low volume concentrations (below 30 percent) than at high volume concentrations (above 45 percent). Although the same trend in the variation of the modulus functions below a frequency level of 150 cycles is exhibited for filler concentrations lower than 45 percent, a reduction in the value of the functions is noticed for filler concentrations above 45 percent. Attempts have been made to give valid explanation to this peculiar behavior. Finally, theoretical relations have been developed for storage and loss modulus of the composite material in terms of the mechanical properties of the constituents and the volume concentrations of the filler. The experimental results have been compared with theoretical values.