High-velocity impact characteristics of 3D auxetic composite cylindrical shell panels: Theory and experiment

The high-velocity impact characteristics of 3D auxetic composite cylindrical shell panels are studied theoretically and experimentally. First, to predict the high-velocity impact parameters, including the residual velocity of the projectile, the energy absorption, and the ballistic limit, an analytical model of such structures consisting of two fiber/resin skins, two adhesive films, and a 3D auxetic lattice core is proposed, in which Reddy's higher-order shear deformation theory is employed to define the displacement variables. After taking into account the equivalent material properties of the core and various failure modes, energy absorption mechanisms, strain rate effect, and impact damage evolution issues of the constituent elements, governing equations and solutions are successfully obtained. To validate the model developed, detailed high-velocity impact tests with different initial velocities are then performed on such shell panel specimens with nylon and metal auxetic lattice cores fabricated by 3D printing technology. Finally, the influences of key geometric parameters of the core on impact properties are investigated, with some important design recommendations being refined to improve the impact resistance and energy absorption capabilities of the studied structure.