Distribution of Micro Stresses and Interfacial Tractions in Unidirectional Composites

A micromechanical approach is developed to determine the micro stress within a unidirectional composite under various mechanical and thermal loading conditions. Based on linear stress—strain relations, the concept of a stress amplification factor is introduced, and the correlations between macro stress and micro stress are explicitly expressed in mathematical equations. Three unit cell models, square, hexagonal, and diamond fiber arrays, are analyzed and compared using three-dimensional finite element methods. Subsequently, effective material properties, the distribution of micro stress in the fiber/matrix, as well as traction distribution at the fiber—matrix interface, and the effect of different interfacial stiffness, are obtained.