The influence of defect shape on the cracking behavior of brittle materials

Abstract

To understand the influence of defect shape on the cracking behaviors of brittle materials, three types of gypsum specimens containing different shape defects are designed, and three-point bending tests have been conducted. The results show that the shape of defects can affect the initiation and occurrence of tensile cracks, as the load continuous to increase, the tensile crack usually propagates along the direction of applied compression. The defect shape can also influence the strength of the specimen, and both tensile and shear cracks occur when the load is close to or greater than 50% of the peak strength. Defects with sharp corners are easy to induce the initiation and occurrence of tensile crack, whereas, for the defects with smooth edges, if the defect area is not large enough, it is difficult to breed tensile cracks. Additionally, defect shape has no effect on the fracture toughness, whereas the defect shape can influence the unstable toughness, and when the defect shape is triangular, the distribution of the unstable toughness value varies randomly, and when the defect shape is trapezoidal, the unstable toughness decreases with the increase of defect area. These results are expected to improve the understanding of brittle fracture and can be used to analyze the durability of concrete structures and the stability of rock slopes.