Numerical simulation of fiber-matrix debonding: Inverse identification of interface properties

Fiber-matrix interface debonding is studied by means of single-fiber epoxy-glass fiber specimens under transverse tensile loading. Experimental observations show abrupt debonding initiation between 67 and 83 deg. followed by stable debonding propagation. Similar abrupt debonding initiation is predicted using the coupled criterion (CC). The latter predicts crack initiation considering both stress and energy aspects from which a range of interface shear and opening critical energy release rates (ERR) and strengths can be derived. Depending on these parameters, initiation is found to be either driven by energy solely or by both stress and energy conditions. The loading required for initiation depends on the opening (mode I) critical ERR and tensile and shear strengths. The debonding arrest angle also depends on the shear (mode II) critical ERR. Consequently, a three steps methodology to identify the interface properties is described and an optimum set of parameters is determined by focusing on the stable debonding propagation after initiation using Linear Elastic Fracture Mechanics.