Influence of temperature and size of the projectile on perforation of graphene sheet under transverse impact using molecular dynamics

In this paper, Molecular dynamics simulation is employed to study the ballistic behavior of single-layer graphene sheet (SLGS) impacted by different sizes of fullerene projectiles and under different temperature conditions. The ballistic performance parameters viz. ballistic velocity limit (Vbl), energy absorption (ΔKEp), and impact reaction force (Fp) on projectile are investigated to understand the perforation mechanics of SLGS. The results under C180 projectile show that at mid-range impact velocity (∼Vbl=4.4 km/s), the projectile sticks to graphene by dynamic covalent bonds (DCB) formation or is trapped. These dynamic covalent bonds are formed and broken concurrently and influence the projectile energy transmitted to SLGS. It is found that for relatively bigger projectile sizes, graphene exhibits greater energy absorption and reaction force. However, the ballistic velocity limit as well as the specific kinetic energy absorbed (Ep∗) by graphene are reduced. The stress distribution shows that for large projectiles, crack propagation is further aided by the axial stress wave reflection. Moreover, the impact test under C180 projectile shows that Vbl and Ep∗ drop by 11 % and 21 %, respectively, when temperature is raised from 1 K to 800 K. In addition, crack patterns of graphene are analyzed, which shows that projectile size and temperature have a great influence in terms of deformation mechanism and crack pattern. Our findings provide useful insights to determine the ballistic performance parameters of graphene impact from different projectile sizes and temperature conditions, which is crucial in order to facilitate their emerging applications such as body armor material and protective shield from orbital debris for spacecraft or satellites.