Effective Permittivity of Shielding Composite Materials for Microwave Frequencies

Due to mass constraints, composite materials are possible candidates to replace metal alloys for electromagnetic shielding applications. The design of standard metallic shielding enclosures often relies on finite-element calculations. But in the case of composite materials, the strong dependence on the shielding properties to the microstructure makes the finite-element approach almost impossible. Indeed meshing the microstructure would imply a huge number of elements, incompatible with usual computational resources. We propose in this paper to develop homogenization tools to define the effective electromagnetic properties of composite materials at microwave frequencies. The ratio between the characteristic size of the microstructure and the wavelength is shown to be a key parameter in the homogenization process. The effective properties can then be used as an input for electromagnetic compatibility standard tools, designed for homogeneous media.