The effect of interfacial imperfections on the micromechanical stress and strain distribution in fibre reinforced composites

A mathematical model for the determination of micromechanical stress and strain distribution in a unidirectional fiber reinforced composites is developed. The model consists of three phases, represented as concentric cylinders, including the existence of an interphase. Both fiber and matrix have well defined elastic properties, while the interphase properties follow an exponential law of variation. The effect of an abrupt variation of elastic properties at the fiber interphase boundary on the micromechanical state of stress is also presented. The degree of adhesion between fiber and matrix is described by means of adhesion parameters introduced, and a parametric study is performed wherein the stress and strain distribution around the fiber are determined as a function of adhesion efficiency and fiber volume fraction. Analytical results were confirmed by means of a finite element technique introduced and applied to the model. (Author)