Delocalization of Impact Energy in Multilayer Graphene Subjected to Supersonic Impact in Vacuum

We employed vacuum micro-ballistic characterization for the first time to explore the ballistic perforation dynamics of multilayer graphene (MLG). The vacuum level is approximately 1/3,000 of the atmospheric pressure to avoid undesired effects from air, including aerodynamic friction of a projectile or a membrane specimen. 3.7 um diameter silica spheres were accelerated to 300 – 900 m/s as projectiles and a suspended graphene membrane was subjected to projectile’s impact. With an ultrafast microscopic imaging system (40 million frames per second), accurate velocities of the projectile before and after penetration were obtained. We studied the residual speed as a function of impact speed. The specific penetration energy of MLG was quantified with respect to projectile’s impact speeds and specimen’s thicknesses. As a result, MLG demonstrated twice better performance in vacuum compared to that in air, opposite to conventional predictions. The penetration features near the impact region were examined by scanning electron microscopy to uncover the correlations with the energy dissipation.