Study of cracks in concrete target under deep penetration by a projectile

A large number of cracks occur in concrete structure after projectile penetration. The study of crack distribution and propagation process is the basis of damage assessment, structural repair and high dynamic fracture mechanism. In this paper, wire saw cutting, X-ray computed tomography (X-CT) and mechanical property testing of damaged concrete were carried out on deep penetration targets. According to X-CT images of radial core samples in target and the mechanical properties of damaged concrete, the crack distribution in the target was divided into a plastic damage zone and a brittle damage zone, and the microcracks only existed in the plastic damage zone. The initial growth process of three-dimensional cracks was obtained by X-CT images of axial core samples in target, that is, the cracks in the pure mortar target gradually developed from the radial direction to the tangential direction, and the target containing coarse aggregate directly formed tangential cracks. The propagation progress of cracks was obtained through the target section, that is, the tangential cracks bent in the pure mortar target, and were relatively straight in the target containing coarse aggregate. A crack propagation model was established, and the tangential crack formula and the crack propagation velocity were obtained.