Additively-manufactured lightweight Metamaterials for energy absorption

Abstract Recent developments in architectural design and additive manufacturing (AM) techniques have led to advances in the design and fabrication of metamaterials. We demonstrate that by precisely designing the architecture of a lattice structure and implementing the accurate and cost-effective capabilities of polymer-based AM, it is possible to create lightweight and strong structures that are highly energy absorbing, able to recover their shape after extreme deformation, and have a high strength-over-weight ratio. Largescale AM lattices with various densities of unit cells were fabricated from two different polymers. The densities of the structures ranged from 66 kg/m 3 to 192 kg/m 3 . Compression experiments established the scaling of their strength and stiffness with their relative density and revealed that the structures were able to recover their original shape after a compression up to 70% strain. The energy absorption efficiency of the structures was 11% higher than Duocel® aluminum foam and comparable to that of aluminum honeycomb, expanded polystyrene (EPS) foams, and Skydex twin hemispheres. These unconventional mechanical properties substantiate the potential of architectural design along with additive manufacturing in various applications, not only at laboratory scale, but also at industrial level.