DISPERSIVE WAVE-PROPAGATION IN A VISCOELASTIC MATRIX REINFORCED BY ELASTIC FIBERS

Abstract

Dispersion and attenuation characteristics of elastic waves propagating in viscoelastic fiber-reinforced composites are studied. The present analysis is based on the multiple scattering formulation for randomly distributed scatterers in an absorbing medium. Frequency-dependent complex material properties of the matrix are estimated from the attenuation coefficients by using the causality relationship between their real and imaginary parts. Pair-correlation functions for finding the accurate average of the T matrix are obtained by Monte Carlo simulation to study the dense fiber system. Resultant effective phase speed and total attenuation of longitudinal and shear waves are presented along the frequency varying the fiber volume fraction. In these results, fluctuations in dispersion and rapid increase in attenuation curves can be observed due to the resonance of fibers. Additionally, the shifts in resonance frequency from the single scattering resonance to higher frequency can be noted as the fiber volume fraction increases. Because the scattering dispersion is not strong in the low-frequency region, the viscoelastic dispersion is dominant in that region. It is possible to determine the dominant range of viscoelastic or scattering dispersion mechanisms depending on the frequency. In conclusion, the effect of the matrix viscoelasticity is very important in multiple scattering formulation for solving practical problems.