Modeling of electrical properties of composites

Abstract

Composites offer a way to design electromagnetic properties simultaneously with other material properties such as mechanical or thermal properties. This thesis describes studies pertaining to the modeling of effective electrical material properties of artificial composites of two separate material phases. This has practical importance because modeling reduces experimental effort when developing novel composites or improving the existing ones. The focus is on materials which have a disordered microstructure, and the scale of inhomogeneities is much smaller than the wavelength. In this thesis, a historical overview about modeling of electrical properties of composites is given. Then a novel method to reduce the computational cost of numerical modeling is introduced. Results are compared to experiments with polymer/ceramic composites. Some problems related to the modeling of the effective permittivity are also pointed out. Novel analytical methods for the modeling of electrical properties of composites are introduced. An equation, which combines desirable properties of two popular mixing equations, is derived. A new method to calculate the effective permittivity and the tunablity of a composite consisting of linear and non-linear dielectrics is given.