THE EFFECT OF INTERFACIAL IMPERFECTIONS ON THE MICROMECHANICAL STRESSAND STRAIN DISTRIBUTION IN FIBER-REINFORCED COMPOSITES

A mathematical model for the determination of micromechanical stress a nd strain distribution in a unidirectional fibre reinforced composite is developed. The model consists of three phases represented as concen tric cylinders, including the existence of an interphase. Both fibre a nd matrix have well defined elastic properties, while the interphase p roperties follow an exponential law of variation. The effect of an, ab rupt variation of elastic properties at the fibre-interphase boundary on the micromechanical state of stress is also presented. The degree o f adhesion between fibre and matrix is described by means of adhesion parameters introduced, and a parametric study is performed wherein the stress and strain distribution around the fibre are determined as a f unction of adhesion efficiency and fibre volume fraction. Analytical r esults were confirmed by means of a finite element technique introduce d and applied to the model.