NEW APPROXIMATION FOR THE EFFECTIVE ENERGY OF NONLINEAR CONDUCTING COMPOSITES

Approximations for the effective energy and, thus, effective conductiv ity of nonlinear, isotropic conducting dispersions are developed. This is accomplished by using the Ponte Castaneda variational principles [ Philos. Trans. R. Sec. London Ser. A 340, 1321 (1992)] and the Torquat o approximation [J. Appl. Phys. 58, 3790 (1985)] of the effective cond uctivity of corresponding linear composites. The results are obtained for dispersions with superconducting or insulating inclusions, and, mo re generally, for phases with a power-law energy: It is shown that the new approximations lie within the best available rigorous upper and l ower bounds on the effective energy. (C) 1998 American Institute of Ph ysics.