Analysis on the effective position of a reinforcement patch used as crack arrest for plates with mixed-mode (I/II) cracks

Abstract

Rectangular patches are usually used as the temporary crack stoppers ahead of the tips of macro cracks. As mixed-mode cracks are usually initiated in engineering structures, the relative position of reinforcement patches to crack tips should be carefully considered. There will be many directions around crack tips for allocating reinforcement patches and the effectiveness of reinforcement patches should be quite dependent on their allocation positions, which can be expressed by the distance between the crack tip and patch, and also the direction of the patch relative to the crack line. The present paper will aim to examine the proper position for allocating the reinforcement patch by comparing the reduction level of the stress intensity factors. Finite element analysis will be conducted for this purpose. The optimum position for allocating the reinforcement patch will be determined, which will be further compared with crack propagation direction determined by strain energy density theory for an elastic cracked body. The conclusion is drawn that the patch with proper stiffness should be allocated in the direction of initial crack propagation near the crack tips. Its effectiveness will not be satisfactory when allocated away from the region.