PROPAGATION OF RADIATION IN HIGH-DENSITY FIBROUS COMPOSITES CONTAINING COATED FIBERS

The dispersion relations of a high-density fibrous composite containing parallel, nonhomogeneous fibers have been derived by a rigorous solution of Maxwell's equations and the application of the quasicrystalline approximation. These formulae are obtained for realistic pair-correlation functions and for an arbitrary incident direction. While the dispersion relations for the effective propagation constants are transcendental equations with a complicated functional dependence, analytical closed-form expressions are obtained in the Rayleigh limit for the hole-correction pair distribution. Numerical results for homogeneous and coated fibers are presented to illustrate the influence of fiber concentration on the extinction efficiency and effective refractive index of the medium. It is shown that the effective refractive index of the medium increases with increasing fiber concentration, due to dependent scattering. As a result, refraction of the transmitted wave occurs, and the angular characteristics of surface emission and reflection would also be affected. Wave refraction is significant at high-volume fraction, and it diminishes with increasing porosity. These results indicate that the radiative properties which rigorously account for the dependent scattering effects must be utilized in order to accurately analyze the thermal performance of high-density fibrous composites.