A predicted approach for determining effective constants of fiber composites with graded interphase

A predicted approach for determining moduli, which include extensional moduli, shear moduli and Poisson's ratio is presented for fiber composites with graded interphase. The approach is derived based on a mechanics of materials formulations for the concentric cylinder assembles model of a single fiber, surrounding matrix, and a graded interphase to account for the chemical reaction and diffuseness which commonly occurs between fiber and matrix. The principles of the displacement compatibility and force equilibrium for each constitutes of the representative volume element, converted to those of Equivalent Square assembles, are used in the process of the derived predicted approach without complicated computations. The validity of the predicted approach is demonstrated versus comparisons with experimental data and some other models existing in the literature. Synchronously, it shows that determining effective moduli of fiber composite with graded interphase by micromechanics equations is a special case of the predicted approach.