Interaction of crack and hole: effects on crack trajectory, crack driving force and fracture toughness

The paper investigates the effectiveness of a circular hole as a crack arrester. A hole represents an elastic inhomogeneity, which is able to attract neighboring cracks, to deflect and stop them from propagating. The interaction between a crack and a neighboring hole is studied, as well as its effects on failure stress and fracture toughness. For this purpose, a numerical model using the configurational force concept and a damage-based approach, the ductile damage plasticity modeling, are combined. In the first part of the paper, an efficient approach is presented to approximate the crack trajectory and the crack driving force in the proximity of a circular hole. The main purpose is to determine the maximum distance at which cracks can be trapped. This is performed for uni- and biaxial loading conditions, and for surface and interior cracks. The second part investigates the improvement in failure stress and fracture toughness, if cracks are trapped by a hole. Hereby perfect and imperfect holes, which contain a defect at the hole boundary, are considered. It is found that the crack trapping distance is affected by the boundary and loading conditions. The increases in failure stress and fracture toughness due to the trapping of a crack depend primarily on the hole size and the defect size at the boundary. The procedures presented in this paper can be applied to composites with arrays of holes or second phase particles of arbitrary shapes.