On the coalescence of collinear cracks in quasi-brittle materials

The coalescence of collinear cracks in a quasi-brittle material is investig ated using the Dugdale-Barenblatt-type cohesive damage zone model. In the c ase of plane stress, two collinear cracks and a periodic row of collinear c racks with equal length are considered. Instead of the fracture criteria in terms of stress intensity factor or crack tip opening displacement, the le ngth of damage localization band is adopted as the control parameter to det ermine the crack propagation in a quasi-brittle material. The crack coalesc ence is attributable to two reasons, namely, the unstable crack propagation due to the high level of the applied stress and the linking of damage loca lization bands. The conditions of crack coalescence are given based on the analysis of the two mechanisms, (C) 2000 Elsevier Science Ltd, All rights r eserved.