Scattering of Waves by Visoelastic Composites and the Characterization of their Dynamic Properties.

Abstract : The propagation of electromagnetic waves in an infinite medium composed of a random distribution of identical, finite scatterers is studied. The T-matrix of a single isolated scatterer, obtained by using the null field equation, is used to make the equations for the field incident on a particular scatterer and the field scattered by it, self consistent. The method we propose is well suited for computations at wavelengths comparable to obstacle size and for non-sphereical obstacles. The attenuation associated with the coherent field as predicted by our computations is compared with the only two sets of experimental results that can be found in the literature. Agreements and discrepancies are examined and the range of validity of the assumed quasi-crystalline approximation is discussed. Further improvements using the coherent potential approximation and the 'self consistent approximation' as well as improved models of the pair correlation function are suggested. (Author)