Analysis of Free Vibration and Low-Velocity Impact Response on Sandwich Cylindrical Shells Containing Fluid

The responses of sandwich cylindrical shells containing fluid to free vibrations and low-velocity impact were studied. The high-order shear deformation theory and Bernoulli’s equation for the structure-fluid interface were used. To solve the equations obtained and validate the results, the Galerkin method and Abaqus finite element software were employed. The main innovation of this research is the calculation of the effective mass of the top layer and the entire sandwich cylindrical shell containing fluid using displacement field relations, their equivalent density, and indentation force due to impact. In addition, to calculate the impact force and the structure-fluid interaction, a two-degree-of-freedom model of mass, spring, and damper with the effect of the crushing resistance of the core was used. The results show that the fluid is an important and effective factor in calculating the natural frequency and low-velocity impact on the structure. The presence of fluid reduces the fundamental natural frequency of the sandwich cylindrical shell by 69%. Parameters such as core and layer thickness, length, and radius of the sandwich cylindrical shell, presence of the fluid, various boundary conditions, wave number, fiber orientation angles, velocity, and mass of the impactor are essential and influential factors in studying vibrations, impact, and optimal design of structures.