A physically based percolation model of the effective electrical conductivity of particle filled composites

The fundamental mechanism of the non-universality of exponent t in the classical percolation equation is discussed on the basis of the comparison of lattice percolation and continuum percolation systems in the present study. The intrinsic universality of percolation exponents is revealed by analyzing the power-law percolation relationship between two different scales (microstructure and macroscopic properties). In view that the classical percolation equation with fitting parameters lacks a clear correlation to the microstructure features, a physically based percolation model is proposed to characterize the effective electrical conductivity of particle filled composites by means of the combination of effective medium (EM) and percolation equations with universal exponents. It is shown that the present model agrees well with the experimental data. Furthermore, the effect of particle shape on the percolation threshold and the effect of electrical conductivity of particle on the effective properties of composites are discussed.