An analytical compressive-shear fracture model influenced by thermally treated microcracks in brittle solids

Natural or artificial brittle solids have numerous randomly distributed microcracks inside. The thermal treatment temperature has an essential effect on the microcrack growth and the shear fracture properties of brittle solids under compression. However, there are few studies on the correlation between thermal treatment temperature, microcrack extension, and shear fracture properties of brittle solids under compression. An analytical model is proposed to evaluate the effect of thermal treatment temperature on the microcrack-induced shear fracture properties (e.g., cohesion, internal friction angle, and shear strength) of brittle solids in compression. The model consists of the micro–macro-model relating microcracks growth, the functions for initial damage and fracture toughness versus temperature, and the Mohr–Coulomb strength criterion. The functions for initial damage and fracture toughness versus temperature are determined from relevant experiments. The sensitivity of thermal treatment temperature, and microcrack parameters to the shear fracture properties of the solid is discussed. A critical angle of the initial crack making the shear strength minimum is found. The experimental research results verify the rationality of the analytical model. This proposed model will have an important theoretical help for the engineering evaluation of brittle solids.