Mitigating performance of elastic graded polymer foam coating subjected to underwater shock

The possible mitigating effect of elastic Density Graded Polymer Foam (DGPF) coating on the marine structure subjected to underwater shock is investigated. A 1-D unified nonlinear finite element model based on the updated Lagrangian frame is built to solve both the transient response of foam coated structure and dynamic cavitation of water near fluid–structure interface. The mitigating effect of DGPF coating with respect to design parameters such as average density, density difference (uneven density), gradient functions and load intensity is explored. It is illustrated that DGPF is superior in underwater shock protection to the equivalent uniform foam if the foam density is properly distributed while load density is not so high. Lower density foam in the water side is helpful to reduce the total impulse transmitted from water. But the total energy absorption capability may be discounted as the coating enters densification phase earlier.