Analytical modeling, solution and experimental validation of high-velocity impact properties of composite hexagonal auxetic honeycomb cylindrical shells

Both theoretical and experimental studies are performed to investigate the impact properties of composite hexagonal auxetic honeycomb cylindrical shells subjected to an internal high-velocity projectile impact. Firstly, an analytical model of composite cylindrical shells with two fiber-reinforced polymer (FRP) skins and a hexagonal auxetic honeycomb core (HAHC) is built to anticipate the high-velocity impact properties, with the delamination and fracture energy absorption mechanisms of the skin and the core being considered. A strain-rate fitting function method is proposed to determine the material properties of the FRP skins and the core considering the strain-rate effect. Reddy's higher-order shear deformation theory is utilized to define the displacement of any point of the structure. Also, an improved Gibson theory is applied to derive the equivalent elastic moduli and Poisson's ratios of the HAHC. A detailed experimental validation is conducted on such shell specimens based on a high-velocity impact experimental system to validate the analytical model, in which comprehensive error analysis is discussed. Finally, the influence of critical geometric parameters of the projectile and the studied shell on its impact characteristics is evaluated and some crucial conclusions are provided to enhance impact resistance.