In this paper, a general matrix cracking model including the effect of fiber/matrix debonding in the crack wake is developed for a unidirectional fiber reinforced composite. The debonding mechanics is incorporated into matrix cracking model by treating the crack-wake debonding as a particular crack propagation problem along the interface. Then, the closed-form analytical solution of the critical stress for the onset of widespread matrix cracking is derived, based on the analysis of steady state crack growth in the matrix. The fracture mechanics approach adopted in the present analysis is compared with the analysis in which the crack-wake debonding mechanics was modeled by energy balance approach. The conditions for attaining no-debonding and debonding as onset of widespread matrix cracking are discussed in terms of the interfacial properties of debond toughness and frictional shear stress. The theoretical results are compared with experimental data that are available in the literature.
