Debonding of adhesively bonded composite patch repairs of cracked steel members

Rehabilitation of steel bridge members using composite patches is increasingly becoming a popular method for fatigue mitigation. However, the long-term performance of these patches is an issue of considerable concern and the focus of ongoing research. In this paper, the debonding (bond failure) of an adhesively bonded composite reinforcement acting on a steel member is investigated. Two debonding scenarios are considered. In the first, a patched, uncracked, steel plate is examined, while in the second, a steel plate with a crack growing into the thickness direction is considered. For the latter scenario, the influence of debonding on the crack driving force is also investigated. To this end, debonding is modelled here as a crack located at the interface between the steel and the adhesive and the finite element method (FEM) is employed in order to determine the strain energy release rate (G), which is a measure of the interface crack driving force and hence characterises the propensity for fatigue-induced debonding.