Micromechanical fiber-matrix interface model for in-plane shear in unidirectional laminae

A novel analytical model is proposed for the in-plane shear response of unidirectional composites on account of fiber-matrix interface. The fiber-matrix interface influences the stiffness and induces nonlinear phenomena, playing a fundamental role in the damage onset and propagation. The interface consists of three zones: fiber-transition, core, and matrix-transition. The transition zones are assumed to have zero thicknesses, while the core zone is a layer with finite thickness. Fiber-transition zone is characterized by a nonlinear damage behavior. The analytical model is verified by comparing with finite element simulations and experimental data, indicating adequate description of the complex phenomena under study.