EFFECTIVE TRANSVERSE RESPONSE OF FIBER COMPOSITES WITH NONLINEAR INTERFACE

This paper presents a framework for the analysis of the constitutive r esponse of composites in which nonlinear behavior originates solely fr om the force-separation response of the interfaces. The direct method of composite materials theory is employed to pass from local nonlinear behavior of a solitary inclusion problem to nonlinear aggregate respo nse. The resulting model, which involves no adjustable parameters, fal ls within the conceptual framework of continuum damage mechanics with ''damage'' variables that have geometrical meaning on the microscale. They are shown to be the expansion coefficients arising in the eigenfu nction representation of the displacement jump at a representative inc lusion-matrix interface. Detailed calculations of stress-strain respon se are carried out for the case of transverse shear and plane dilatati on of unidirectional fiber composites in dilute concentration. Bifurca tion of equilibrium separation in the solitary inclusion problem is sh own to precipitate instability in composite response. Interfaces are a ssumed smooth and such that normal separations are governed by the non linear force law of Ferrante et al. (1982). Comments on the extension of the formulation to include the effects of finite concentration are provided as well. (C) 1998 Elsevier Science Ltd. All rights reserved.