Experimental and numerical simulation of three-point bending fracture of brittle materials with inverted T-shaped obstacle cracks

In rock materials, the interaction and coalescence of three-dimensional internal cracks play a fundamental role in material failure and instability. This study focused on the generation of three-dimensional internal cracks inside specimens using the three-dimensional internal laser-engraved crack (3D-ILC) method, without causing surface damage. Experimental and numerical investigations were conducted to examine the fracture behavior of brittle solid materials with and without obstacles during three-point bending tests. The experimental results revealed that obstacle cracks positioned horizontally in an inverted T configuration exhibited a shielding effect on the vertical cracks, resulting in reduced propagation velocity and decreased curvature at the lower tip of the vertical cracks. Crack initiation and propagation were promoted in the presence of obstacle cracks, forming distinct fracture patterns, such as pear-shaped and hook-shaped configurations. While the overall failure mode of the specimens was not significantly altered by the presence of obstacle cracks, dynamic fracture dual sources, and new Mode III cracks were observed on the fracture surfaces. The 3D-ILC method provided an effective means for studying the integration and penetration of pre-existing three-dimensional internal cracks. The findings of this study contribute to the theoretical understanding of fracture propagation through obstacles in brittle materials and provide a basis for further investigations using physical experiments.