WEB Hierarchical nanostructured aluminum alloy-coated micro-architectured materials and their mechanical properties
Mechanical metamaterials are a new possibly important direction for topological materials due to the novel mechanical properties, such as negative Poisson’s ratios and negative compressibilities. By integrating the concept of hierarchy and size effects, micro/nano-architected metamaterials fabricated by two-photon lithography with metallic or ceramic coating can be ultra-strong but light. However, the attainment of both strength and ductility is generally mutually exclusive, which restricts the applications of these materials in energy storage/absorption and mechanical actuation. Here, we design a metamaterial that can withstand high load while keeping low density. We utilize the ‘supra-nanometre-sized dual-phase glass-crystal’ metallic film on the 3D printed polymeric structure. The dual-phase nanostructuring achieves an ultra-high yield strength and large plasticity at the same time. Despite a thick metallic coating usually causes catastrophic collapse, our metallic metamaterial shows recoverability during compression and exhibits 90 times increase in strength after coating. In situ mechanical testing and computational works reveal ductile-like deformation owing to the plastic flow in the dual-phase structure of the film and the impact absorption by the architecture of the metamaterial. We demonstrated that our micro-architectured metamaterial can occupy regions of material property space (high strength and ductility at low density) that were hitherto empty. Our results create the architected multi-material systems that would open the property space even further and could be used to impart enhanced functionality, making programmable stiffness, and tailored energy absorption all possible.