Transport properties and percolation in two-phase composites

The transport properties in two-phase (Ac, M) granular composites generally depend on several parameters: the interfaces (Ac/Ac, M/M, Ac/M), the grain sizes and morphologies, the percolation threshold. Generally in such (Ac, M) composites, one of the component (M) plays a mechanical role, and an oth er (Ac) presents a transport property as electron conduction, superconducti on, or ionic conduction. We present here the various simulation approaches which can be used to better understand the final properties of such composi tes. Two types of composites can be considered: sintered two-phase composit es in which chemical diffusions and interphase formation occur at the inter faces, polymer/ceramics composites in which weak links are involved between grains. To better understand the transport properties in two-phase composi tes three types of approaches are presented: (1) a microstructural approach ; (2) the effective medium approximation; (3) the percolation theory. Sever al examples are selected to illustrate and discuss these various approaches . (C) 1999 Elsevier Science B.V. All rights reserved.