  The excellent mechanical properties of graphene have enabled it as appealing
candidate in the field of impact protection or protective shield. By
considering a monolayer graphene membrane, in this work, we assessed its
deformation mechanisms under hypervelocity impact (from 2 to 6 km/s), based on
a serial of in silico studies. It is found that the cracks are formed
preferentially in the zigzag directions which are consistent with that observed
from tensile deformation. Specifically, the boundary condition is found to
exert an obvious influence on the stress distribution and transmission during
the impact process, which eventually influences the penetration energy and
crack growth. For similar sample size, the circular shape graphene possesses
the best impact resistance, followed by hexagonal graphene membrane. Moreover,
it is found the failure shape of graphene membrane has a strong relationship
with the initial kinetic energy of the projectile. The higher kinetic energy,
the more number the cracks. This study provides a fundamental understanding of
the deformation mechanisms of monolayer graphene under impact, which is crucial
in order to facilitate their emerging future applications for impact
protection, such as protective shield from orbital debris for spacecraft.
