Modeling of Interphase Formation on Unsized Fibers in Thermosetting Composites

The interphase is the region between the fiber and matrix whose properties strongly influence the overall composite behavior in terms of mechanical strength, chemical and thermal durability. The composition and thickness of the interphase region is governed by the processing conditions, in addition to the fiber surface treatments and other characteristics of the fiber and the resin materials. One of the strong contributing mechanisms to interphase formation is the preferential adsorption of matrix components onto the fiber surface, which takes place on the order of molecular scales. Chemical reaction in the matrix also happens simultaneously with the adsorption process. In this paper, a multi-layer adsorption-desorption-reaction model for a binary fluid mixture in contact with a solid surface is implemented to study the kinetics of interphase formation near bare fiber surfaces in thermosetting composite systems. Composition and thickness evolution of the interphase are predicted as functions of time. Conditions that lead to interphase formation upon vitrification are identified. Parametric studies are presented to investigate the effects of various nondimensional groups on the interphase region development.