Electromagnetic Diffraction by a Narrow Slit in an Impedance Sheet--E-Polarization

摘要

Composite materials have come into use lately in aircraft construction because of their high strength and low weight. This report examines a method for computing the shielding effectiveness of a narrow slit in a composite material. This corresponds to a joint or seam between two composite panels. For low frequency incident fields, the composite can be effectively modelled as an infinitely thin impedance sheet. The literature on impedance sheets is reviewed and a general integral equation formulation for impedance sheets is described. Since only narrow slits (seams) are of practical interest, a quasi-static (low frequency) approach is developed. A dual integral equation is derived for the problem. The dual integral equation is reduced to a Fredholm second kind integral equation. This integral equation is solved by expanding the unknown in terms of Legendre polynomials. An analytic solution for the problem of a narrow slit in a perfectly conducting plane is also obtained. (Author)