A fractal model for the static coefficient of friction at the fiber-matrix interface

The physical, geometrical, and mechanical properties at the fiber/matrix interface of a fiber-reinforced composite material have a dominant effect on the overall mechanical behavior of these materials. Specifically, the toughening of these materials is largely attributed to the energy dissipation due to the frictional sliding of fibers at their interface with the matrix material. The micromechanisms involved with interfacial failure and sliding are currently not entirely understood, and the failure threshold is generally predicted using macro-scale friction laws which neglect the micromechanical aspects. The objective of this study is to explore the derivation of a macro-scale static coefficient of friction at the interface of a previously debonded fiber based on the micro-scale properties of the contacting surfaces. Presented results illustrate that the macro-scale static coefficient of friction obtained from the proposed micro-scale model is independent of the normal load and is therefore consistent with the classical Amontons-Coulomb phenomenological laws of friction.