Influence of nearby fiber on fiber–matrix debonding: Coupled Criterion prediction and debonding shape determination

Fiber-matrix interface debonding in two-fiber specimens under remote tensile loading is studied both experimentally and numerically by means of a coupled stress and energy criterion. Depending on its relative position, the neighboring fiber induces a perturbation of both stress and energy fields at the reference fiber interface which results in asymmetrical debonding initiation and propagation. The determination of the debonding initiation and propagation shape is addressed based on either i) stress isocontours, ii) energy isocontours or iii) the Coupled Criterion (CC). It was found that the debonding initiation configuration can be determined based on stress (respectively energy) isocontours for small (respectively large) enough interface brittleness number. For intermediate brittleness number, the debonding initiation configuration cannot be obtained using neither the stress nor the energy isocontours, but requires a coupling of both aspects. Despite different initiation debonding configurations, the corresponding initiation remote stresses do not differ much, which results in similar debonding configurations after unstable crack propagation following initiation.