COMPOSITES WITH FUNCTIONALLY GRADED INTERPHASES - MESOCONTINUUM CONCEPT AND EFFECTIVE TRANSVERSE CONDUCTIVITY

We consider a unidirectional fiber-reinforced composite with an interp hase between the fiber and matrix taken as a graded zone of two random ly interpenetrating phases of these materials. In particular, we take this interphase as a functionally graded material (FGM). The objective of this paper is to present a micromechanics based method to treat FG M and to calculate the effective macroscopic properties (transverse co nductivity, or, equivalently, axial shear modulus) of such a composite material. This problem requires the treatment of several length scale s: the fine interphase microstructure, its mesocontinuum representatio n, the fiber size, and the macroscale level (of many fibers) at which the effective properties are defined. It is shown through an example t hat a convergent hierarchy of hounds on the effective response is obta ined with systematically increasing mesosale resolutions.