LIMITATIONS OF THE UNCOUPLED, RVE-BASED MICROMECHANICAL APPROACH IN THE ANALYSIS OF FUNCTIONALLY GRADED COMPOSITES

A new class of materials, called functionally graded composites, has recently evolved in which the microstructure is tailored to meet specific applications. This is accomplished by distributing the reinforcement phase in a nonuniform manner, resulting in statistically inhomogeneous composites. The standard micromechanical approach used to analyse the response of this class of materials is to decouple the local and global effects by assuming the existence of a representative volume element at every point within the composite. Recently, a new micromechanical theory, which couples the local and global effects, has been developed and applied to functionally graded composites. Herein, this theory is used to assess the limits of applicability of the standard micromechanical approach in predicting local stresses in the fiber and matrix phases of functionally graded composites subjected to a thermal gradient. It is shown that the simplified uncoupled approach is inaccurate when the dimension of the reinforcement phase is large relative to the dimension of the composite.