Effect of Projectile Geometry on Dynamic Mechanical Response of Graphene

In order to explore the influence of projectile geometry on the dynamic mechanical response of graphene, two projectile designs with different shapes and different structural size ratios under the same shape have been considered using molecular dynamics simulation. The mechanical response of single/multi-layer graphene under impact was studied by characterizing the residual velocity of the projectile, kinetic energy consumption, the damage state of graphene and the propagation state of stress wave. The results show that the residual velocity and kinetic energy consumption of different shapes of projectiles impacting graphene can be roughly divided into three regions with the change of impact velocity. The impact of spherical and hemispherical projectiles is similar, but cylindrical projectiles exhibits large difference. The damage of graphene by cylindrical projectiles is stronger than those by spherical and hemispherical projectiles, and the fractal theory model can quantitatively describe the morphology of graphene holes. The “barrier effect” generated by the flat head of cylindrical projectiles can better explain the ballistic limit velocities of penetrating monolayer and bilayer graphene, which are lower than or close to those of spherical and hemispherical impact, respectively. For the same shape of hemispherical projectile, the penetration capability increases with the increase of the size ratio, but the enhancing effect brought about by the increase of the size ratio does not last continuously.