Bonded repair of cracks under mixed mode loading

Abstract

The problem of assessing the effectiveness of a bonded repair to a cracked plate can be reduced to a one-dimensional integral equation for the special case when both the plate and the reinforcement are isotropic and have the same Poisson's ratio. This special case is used here to highlight some aspects of bonded repair efficiency under mixed mode loading which are not captured by crack bridging models. It is shown that bonded repair is less efficient in reducing the stress intensity factor under mode II than mode I, although the stress intensity factor under the shear mode also asymptotes to a limiting value as has been previously shown for the tensile mode. A closed form solution is derived for the limiting value of the stress intensity factor under shear mode. It is shown that for the long crack limit, the appropriate two-dimensional idealisation of the representative bonded joint corresponds to a plane strain condition, and the existing asymptotic solution for tensile mode needs to be modified to accommodate the effect of Poisson's ratio on the stress intensity factor. It is also noted that crack bridging models lead to non-conservative predictions of repair efficiency for short cracks.