Mechanism of polyurea in protecting liquid-filled square aluminum tube from the impact of high-velocity projectile

The impact of projectile on liquid-filled containers produce hydrodynamic ram (HRAM), which results in local damage and overall deformation of the container. Aiming at enhancing the protection capability of liquid-filled containers under projectile impact loads, this study proposes a scheme of spraying polyurea on liquid-filled containers. Calibrated numerical modeling with an experiment was conducted to investigate the dynamic response process of the polyurea coated water-filled square aluminum tube (PCST) under the high-velocity impact of projectile. The effects of projectile velocity (700-1100 m/s) and polyurea thickness (0-6 mm) on the damage characteristics of the liquid-filled containers were analyzed and summarized. Results showed that the strength of HRAM increased with the rise initial velocity of the projectile. The polyurea layer reduced the plastic deformation of the square aluminum tube, restricted the crack expansion of the corner, and wrapped the petaling failure of the tube. The restraining action of the polyurea coating on the deformation of the container enhanced the peak pressure in the liquid, whereas the deceleration of the polyurea layer on the projectile weakened the deformation of the tube. A competitive relationship existed between the restraining action of the container and the deceleration effect of the projectile on HRAM. With the increase in polyurea layer thickness, the strength of HRAM trended to initially increase and then decrease. The leading cause of HRAM was gradually changed from container restraint action to projectile deceleration effect.