Study on the impact performance of sandwich hollow cylinders hitting water based on SPH method

The impact performances of one monolithic cylinder and two sandwich cylinders during water entry are investigated by SPH method, which is validated by an existing experiment. The first cylinder is made of aluminum alloy (AL cylinder), the second cylinder is made up of polyurethane core and aluminum alloy layers (AL-PU-AL cylinder), and the third cylinder is made up of aluminum alloy core and polyurethane layers (PU-AL-PU cylinder). All the cylinders have the same size. The research shows that the stress levels and deformations of the cylinders are closely related to the impact forces and their inherent strengths and stiffnesses. The deficiency of the AL-PU-AL cylinder lies in its poor inherent strength and stiffness, resulting in the greatest stress level and deformation under the same initial conditions. The deficiency of the AL cylinder lies in its large impact force at the same initial velocity, which may lead to a high stress level. In contrast, the impact force and inherent strength and stiffness of PU-AL-PU cylinder are moderate, contributing to a lowest stress level at the same initial velocity and a stress level slightly higher than that of AL cylinder at the same initial kinetic energy.