Systematic design of high-strength multicomponent metamaterials

Highlights: • The properties of the material of outer elements will dominate the overall properties of the lattice structure; • A bilinear behavior in the Force-Displacement curve of the individual unit cells with free lateral elements is revealed • Stress-controlled instabilities are identified in octet-truss lattice structures; • A critical displacement is found at which the elastic energy becomes independent of the printing parameters. -- Abstract: The emergence of additive manufacturing, along with the introduction of the concept of metamaterials, allows the synthesis of high-performance materials with superior specific strength. With recent advances in printing multi-material structures, the design space of metamaterials has exponentially grown. Variation in dimensions of the printed metamaterials due to limitations of the manufacturing process can drastically offset their performance compared to their original design. So far, the impact of deviations in the manufactured metamaterials and their effect on their final performance has not been studied systematically. There are also no guidelines for selecting materials in a multi-material lattice structure to achieve higher mechanical performance. Here, the strength and toughness of printed single- and bimaterial lattice structures with a combinatorial selection of materials and their sensitivity to the printing parameters are studied. We show that the exterior elements dominate the overall mechanical performance of the metamaterial compared to the internal elements. We found two regimes of slow and fast softening in periodic lattices. We study the sensitivity of the mechanical performance of the printed metamaterial to variations in the thickness of internal and exterior elements in detail.