Nano- and micromechanical testing of graphene have previously revealed a number of attractive properties, including exceptional strength and stiffness, attributable to the covalent bonding between carbon atoms in the single-atom layer. So far its mechanical properties have been mainly investigated under quasistatic loading; response to dynamic loads is relatively unknown. Jae-Hwang Lee and colleagues now explore this regime by performing impact testing by firing single micrometre-sized silica spheres at supersonic speeds at multilayer graphene, achieving strain rates of ∼107 s−1. They report that the penetration energy can be 8–12 times those of literature values for steel, at equivalent projectile velocities. This result can be explained in part by a large in-plane speed of sound — resulting from graphene's low density and high stiffness — that permits rapid delocalization of concentrated stresses during projectile impact, mitigating premature failure. Such high resistance to failure under dynamic loading, coupled with it now being possible to synthesize large-area sheets, might make graphene an option in composite armour systems.
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Plummer, J. Supersonic impact. Nature Mater 14, 134 (2015). https://doi.org/10.1038/nmat4208
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DOI: https://doi.org/10.1038/nmat4208
