Analysis and measurement of permittivity in composite materials at low frequencies

This paper focuses on the measurement of the effective permittivity εeff in composite structures. A reconsideration of some concepts related to the measurement of effective permittivity for dielectric media and compositematerials at low frequencies is discussed. In particular, the possibility to measure the average electric displacement and electric field over a region of interest on the basis of the circulation law of the magnetic field by the use of properly shaped Rogowski coils is analyzed. A three-dimensional finite element analysis is carried out to simulate the effective magnetic permeability of a composite materials with the aim to find analogy between the two macroscopic electromagnetic parameters.