Fracture of brittle material with two 3D parallel internal cracks under thermal stress: Experimental and numerical analysis

Many defects such as cracks are often present inside brittle solids, and most of the cracks do not appear in a single form. The fracture and failure of brittle solids are basically caused by the interaction and expansion of multiple cracks. Most of the traditional studies on this topic have focused on surface or penetration crack interaction under tensile and compressive loads, while there have been very few studies on the expansion characteristics and interaction of parallel internal cracks under temperature loading. This study applies the 3D internal laser-engraved crack (3D-ILC) method to fabricate parallel internal cracks inside the 3D cube. Physical tests and numerical simulations of parallel internal cracks of different sizes and single crack propa-gation under temperature fields are carried out, and the propagation characteristics of internal cracks and the interaction between parallel internal cracks of unequal size under temperature loading are investigated. The study results show that the big crack will inhibit and shield the expansion of the small crack. In addition, there are typical "anti-binary tree" mode III features on both sides of the parallel large crack and single large and small crack propagation surface, which are classified as mixed I-II-III crack, while the parallel small cracks are mode I-II. Compared with the quasi-static crack growth criterion, the simulation results of the subcritical crack growth criterion are more in line with the physical test results, and there is a subcritical growth phe-nomenon in the parallel crack propagation under the temperature load. The results provide experimental and theoretical references for the study of 3D bi-parallel cracks interaction of different sizes and the fracture of mode I-II-III crack under the temperature field.