Transient underwater shock response of sacrificed coating with continuous density graded foam core

The transient response of a one-dimensional sacrificed coating with Continuous Density Graded Foam (CDGF) cores subjected to underwater shock is numerically studied. A unified nonlinear finite element model based on the updated Lagrangian frame is developed to simultaneously solve both the transient response of foam coating and the cavitation of water. The potential mitigation effect of the CDGF coating with respect to the designing parameters such as average density, gradient function and load intensity is discussed. It is shown that the response of coating is mainly controlled by its global compressive behavior as the fluid-structure interaction elongates the total loading time. Therefore, the non-uniform distributed CDGF core cannot prominently enhance the performance of sacrificed coating for the shock wave with long duration. When the gradient is large, it is helpful in reducing the total impulse transmitted from water, but the total energy absorption capability may be discounted as the coating partly enters the densification phase earlier.