The macroscopic failure of brittle materials normally originates from the unstable propagation of one or multiple dominant cracks, which evolve through the coalescence of distributed internal microcracks and defects. This study focuses on common defects containing both tip and curved-segment features, abstracted as lip-shaped cracks, and establishes corresponding failure criterion. A periodically distributed lip-shaped multiple crack model was developed to investigate three critical factors affecting crack interactions: crack inclination angle, crack width-to-length ratio, and crack spacing, by which four coalescence patterns were predicted. Validation was conducted via coalescence simulation and comparation with literatures’ experiments. The coalescence mechanisms and impact on performance of lip-shaped multiple cracks were ultimately revealed. The principal conclusions are summarized as follows: (1) Four coalescence patterns of lip-shaped multiple cracks were summarized, thereinto the most common coalescence pattern is the coalescence between tip and abdomen. The coalescence pattern is most sensitive to the change of crack inclination angle;(2) Compared with the experimental results, this study successfully simulates the complex coalescences in brittle materials; (3) The crack inclination angle and spacing of lip-shaped cracks have a significant impact on the performance of the model: the smaller the crack inclination angle, the smaller the tensile strength and the greater the stiffness of the model; the smaller the crack spacing, the smaller the model failure displacement.
