A thin-shell shape adaptable composite metamaterial

Abstract Mechanical metamaterials undergoing extreme deformations span an ever increasing design space of mechanical performance. However, achieving selective deformability in load-carrying metamaterials remains unexplored. Anisotropic thin fiber-reinforced composite shells, which are soft in bending and stiff axially, present an attractive option for addressing this challenge but are difficult to realize in practice due to fabrication complexity. In this work, an integrated fabrication technique enabling single-step curing of complex composite mechanical metamaterials is proposed. By using 3D-printed tooling and silicone spacers, composite assemblies can be cured in an autoclave without the need for post-cure bonding of individual shells. The technique reduces manufacturing times and eliminates adhesive bonds, which add mass to the structure and can be points of failure. The proposed technique is demonstrated on a modified rotating square auxetic metamaterial geometry, with fabricated prototypes withstanding up to 60% global tensile strains elastically. The composite anisotropy is, moreover, used to control the deformation mechanism in the metamaterial, thereby delaying failure of the structure and allowing tunability of elastic properties. This work sets the stage for the use of composites as a means of expanding the design space achieved by mechanical metamaterials for shape adaptation in lightweight, load-carrying applications.