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

Dispersion and attenuation characteristics of elastic waves propagatin g 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 co mplex material properties of the matrix are estimated from the attenua tion coefficients by using the causality relationship between their re al and imaginary parts. Pair-correlation functions for finding the acc urate average of the T matrix are obtained by Monte Carlo simulation t o study the dense fiber system. Resultant effective phase speed and to tal attenuation of longitudinal and shear waves are presented along th e frequency varying the fiber volume fraction. In these results, fluct uations in dispersion and rapid increase in attenuation curves can be observed due to the resonance of fibers. Additionally, the shifts in r esonance frequency from the single scattering resonance to higher freq uency 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 th e matrix viscoelasticity is very important in multiple scattering form ulation for solving practical problems.