A FRACTAL MODEL FOR THE STATIC COEFFICIENT OF FRICTION AT THE FIBER-MATRIX INTERFACE

The physical, geometrical, and mechanical properties at the fiber/matr ix interface of a fiber-reinforced composite material have a dominant effect on the overall mechanical behavior of these materials. Specific ally, the toughening of these materials is largely attributed to the e nergy dissipation due to the frictional sliding of fibers at their int erface with the matrix material. The micromechanisms involved with int erfacial failure and sliding are currently not entirely understood, an d the failure threshold is generally predicted using macro-scale frict ion laws which neglect the micromechanical aspects. The objective of t his study is to explore the derivation of a macro-scale static coeffic ient of friction at the interface of a previously debonded fiber based on the micro-scale properties of the contacting surfaces. Presented r esults illustrate that the macro-scale static coefficient of friction obtained from the proposed micro-scale model is independent of the nor mal load and is therefore consistent with the classical Amontons-Coulo mb phenomenological laws of friction. Copyright (C) 1996 Elsevier Scie nce Limited