Molecular dynamics study of the mechanical behaviour of ultrathin polymer–metal multilayers under extreme dynamic conditions

Abstract

Recent microprojectile impact tests have revealed that ultra-thin polymer films possess superior specific penetration energy, about ten times more than that of conventional armour materials. On the other hand, it is well established that metallic nanostructures demonstrate extraordinary mechanical properties. Therefore, it may be possible to achieve structures with superior dynamic performance by arranging ultrathin polymer and metal films in multilayer architectures. In order to test this hypothesis, we conducted molecular dynamics simulations of ballistic impact tests of multilayer aluminium-polyurea nanostructures. The computed specific penetration energy of a polymer–metal bilayer is 42% higher than the highest experimentally measured value for any material at a similar impact speed. Moreover, an aluminium layer confined between two polyurea layers has approximately 40% less impact-induced dislocations compared to an aluminium layer which is in contact with only one polyurea layer. This observation clearly demonstrates that the polymer exerts remarkable resistance on the dislocation nucleation in the metallic layer. Our results propose a potential bottom-up design pathway to develop structures with superior dynamic performance.