A study of stress distribution in model composites by finite-element analysis. II. Fiber/matrix interfacial effects

Finite-element analysis, in conjunction with a spectroscopic mechanical method, has been applied in a study of stress distribution in fiber reinforced model composites. In this study, special emphasis was devoted to an understanding of variation of stress distribution with changing fiber/matrix interfacial properties. Experimental studies were focused on the effects of coating properties of an anisotropic polydiacetylene fiber in an epoxy matrix. Stress transfer efficiency and stress distribution curves were shown to be clearly dependent on the nature and thickness of the interface, although the effects of a thin coating are limited. Lower stress transfer efficiency, even failure, was observed for thicker coatings. Calculated results, utilizing the finite element method for model composites, agree qualitatively well with experimental data. A detailed description of possible failure modes for the discontinuous fiber composites has been developed from these finite-element calculations.