Three-dimensional crack propagation behaviors of transparent brittle materials under blasting load

The crack propagation behavior of brittle materials, such as rock, is often challenging to capture under explosive loading conditions. To address this issue, model experiments were conducted based on the theory of explosive damage, utilizing transparent polymethyl methacrylate as a surrogate material to simulate the fracture response of brittle materials. High-speed photography and computed tomography scanning were employed to investigate the dynamic fracture process and three-dimensional crack evolution under blast loading. In addition, 3D scanning technology was used to reconstruct the morphology of cracks and characterize the fracture surface features. The results indicate that under the sustained action of multi-stage explosive energy, cracks undergo repeated initiation and propagation. Initial cracks induced by shock waves exhibit high density and a “fish scale” pattern, primarily concentrated around the blast hole. In contrast, secondary cracks driven by detonation gases have a lower density and extend outward in “ear-shaped” or “dagger-shaped” forms. As the distance from the explosion center increases, the crack surface morphology transitions from rugged to microwave-like textures, with improved flatness. Specifically, the elevation variance of the fracture surface decreases from 0.796 to 0.586, while the maximum height reduces from 3.2 mm to 2.8 mm, representing a 12.5% reduction. Moreover, the failure mode of the material shifts from compressive-shear to tensile failure with increasing distance from the explosion center. This shift is accompanied by a decline in both the fractal dimension of the crack distribution and the overall damage degree of the model.