Electromagnetic Properties of Syntactic Foam Composites

Abstract

A numerical model based upon renormalized effective medium theory will be described. The model successfully predicts the frequency dispersive permittivity of finite thickness dielectric/ conducting microsphere composites, electrically lossy syntactic foams, where the conducting particulates have volumetric fraction of 0 to 50%. The composites display unique frequency dispersions which are associated with the composite dimensionality and fractal-like sphere surface morphology. Theory and measurement show the composites have critical volume fractions which can be 20% above theoretical values for conducting spheres, i.e 27-–31% and the frequency dispersion of the composite permittivity can be varied by controlling the nanoscale surface morphology and composite thickness. Supporting permittivity measurements in the frequency range of 1–100 GHz will be presented.