Mechanical properties of hybrid metamaterial with auxetic chiral cellular structure and silicon filler

Hybrid metamaterial with auxetic cellular structure and silicon filler was manufactured and mechanically tested for the first time with aim to study its enhanced mechanical properties. The uniform and graded base specimens with auxetic chiral cellular structure were fabricated from copper alloy using the Selective Electron Beam Melting (SEBM) method. The fabricated specimens were then fully infiltrated with silicone filler under vacuum conditions to avoid any voids (air gaps) and to achieve a high degree of homogeneity in the composite structure. The mechanical behaviour of hybrid specimens under quasi-static and dynamic compressive loading conditions was investigated experimentally. The results show that hybrid specimens with auxetic cellular structure and silicon filler exhibit much better mechanical response with increased stiffness and smooth response in comparison to specimens with conventional (non-hybrid) auxetic cellular structure. They also have a higher plateau stress but lower densification strain and possess much higher energy absorption capacity in comparison to the base specimens with chiral auxetic structure. This is attributed to the interaction between the filler and the structure, which results in the improvement of the macroscopic mechanical properties.