Coupled dynamic characteristics of the hull and cushioning structure of high-speed water entry vehicle

To mitigate the extreme mechanical challenges posed by peak and intense instantaneous impacts during high-speed water entry, this paper proposes a rigid polyurethane foam (RPUF) filled cushioning structure to absorb impact energy and minimize hull deformation. The mechanical properties and constitutive parameters of RPUF are characterised by dynamic and static compression tests. The coupled Euler–Lagrange method was used to perform numerical simulations of the water entry process for vehicles equipped with cushioning structure. The load mitigation efficiency of the cushioning structure, as well as its deformation and failure modes, were comprehensively examined. Additionally, based on the response surface methodology, an analysis was conducted to evaluate the influencing factors contributing to the deformation of the vehicle's hull structure. The research results show that the load reduction efficiency can reach a minimum of 50% under various conditions, with a maximum load reduction efficiency of 80.1% and a maximum structural deformation reduction of up to 57.1% being achieved under certain conditions. It is also observed that the density of the RPUF material has a significant effect on the load reduction efficiency, while the strain rate effect has a relatively small effect. As the Froude number increases, the load reduction efficiency of the cushioning structure decreases and the deformation of the vehicle hull increases.