EFFECTS OF INTERPHASES ON THE TRANSVERSE STRESS-STRAIN BEHAVIOR IN UNIDIRECTIONAL FIBER-REINFORCED METAL-MATRIX COMPOSITES

In the context of continuum mechanics, the interfaces between the fibe r and matrix are often assumed to be perfect. However, in many fiber r einforced composites, the bond between the fibers and the matrix mater ial is not of the perfect kind that can be modeled by a continuity of traction and displacements across the fiber-matrix interface. Instead, the bond is affected across a thin interfacial zone, an interphase, w hich has distinct properties from the fiber and matrix. In this paper, a framework has been established to characterize the effects of disti nct interphases in the study of fiber reinforced composites. On the ba sis of this framework, a rigorous analysis has been carried out for th e transverse normal loading of a unidirectional fiber reinforced compo site. It is assumed that such an interphase is created deliberately by coating the fibers with a third phase material. By the use of the fin ite element method, a numerical analysis for a basic cell provides res ults for the micromechanical fields of stresses and the macromechanica l properties of the composite, with and without partial interphase fai lure. In addition, an analytical estimation scheme to predict the tran sverse effective stress-strain relation is developed by using a modifi ed Mori-Tanaka method. Satisfactory agreement between the analytical e stimates and the numerical solutions is found.