Effects of sacrificial coatings on stiffened double cylindrical shells subjected to underwater blasts

Underwater explosion shock loadings can seriously damage the vitality and fighting capacity of warships. Plastering a layer of sacrificial coating on the ship hull is one of effective strategies to isolate shock impulses and absorb shock energy. In this paper, the shock mitigation effects of sacrificial coatings plastered on a stiffened double cylindrical shell are analyzed numerically. The numerical models are validated by conducting a series of physical experiments of a stiffened double cylindrical shell under noncontact underwater explosion. Three different configurations are considered: both the pressure and thin hulls are plastered with sacrificial coatings; only the thin hull is plastered with sacrificial coatings; and only the pressure hull is plastered with sacrificial coatings. The total pressure field in water and the dynamic response of the stiffened double cylindrical shell are obtained. The results indicate that the deformation and motion of the sacrificial coatings can more easily generate rarefaction wave, which can decrease the total shock impulse acting on the structure. Among three configurations, the configuration of the coating plastered on the thin hull has a better capability of isolating the shock impulse and reducing the shock loadings transmitted to the pressure hull. The dynamic stress and velocity responses of the shell are effectively decreased. Comparisons between different configurations suggest that the coating on the thin hull plays a key role in mitigating shock loadings, while the coating on the pressure hull has limited effects. Moreover, comparison results between the bare hull and the equivalent model which increases the thickness of the thin or pressure hulls under the same mass conditions indicate that the method of using a sacrificial coating is more effective in improving the blast resistance of the structure. The research results are useful in guiding the shock resistance design of stiffened double cylindrical shells.