Scattering from composite materials: a first-order model

The nonspecular electromagnetic scattering from finite composite laminates is investigated. The composite material is modeled as planar lamina composed of undirectional collimated fibers with regular spacings between the elements. The fibers, perfectly or partially conductive, are assumed to be embedded in a resin matrix translucent to electromagnetic radiation. For the partially conductive case, the Schelkunoff Ansatz is used. The case of two-plied laminates with skewed fiber orientation is discussed. The mathematical formulation is based on the electric-field integral equation solved with an entire-domain Galerkin expansion. Results are obtained for laminates with both finite and infinite numbers of elements. For the latter, the Floquet-Galerkin solution for periodic structures is used. The effect of truncation of the panels is discussed for arbitrary angles of illumination. It is shown that in many cases implementation of the Floquet-Galerkin solution using diagonal system matrices yields accurate results for the nonspecular cross sections of the laminates. The theoretical results are confirmed by experimental data.<
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