Characterization of Additively Manufactured Mechanical Metamaterials

Abstract

Designing materials that are lightweight while achieving a desirable combination of mechanical, thermal, and other physical properties is an aspiration in material science. Lattice structures are suitable aspirant to achieve lightweight with precisely tailored mechanical properties because of their porous structures, well-defined geometries of their unit cells, high strength to weight ratio, compared to traditional structural materials. Mechanical metamaterials are engineered structures with unique mechanical properties such as negative Poisson’s ratio and bistability which vary dramatically from those of the base material. The unique properties of mechanical metamaterials require accurately fabricated arrangements of ligaments in intricate, periodic structures. AM processes, such as Fused Deposition Modeling (FDM), are able to produce these structures with filaments, such as Thermoplastic Polyurethane (TPU), Polylactic Acid (PLA) which enable precisely fabricated lattice structures. Although recent advancement in AM techniques has enabled the fabrication of various lattice metamaterials with unique properties, still, the cogent designs of mechanical metamaterials with programmable stiffness of auxetic structures and multistability are still difficult and exciting topics. In this regard, we explore the two domains of mechanical lattice metamaterials (i) designing auxetic metamaterials with programmable stiffness and (ii) exploiting planar and cylindrical bistable lattices for mechanical response and energy absorption. These emergent domains indicate the transitioning of mechanical lattice metamaterials from traditional materials to smart, adaptive, and versatile materials, which has applications in realistic problems in energy absorption devices, wearable devices, and robotics, and continue to push the boundary of possibilities of architected metamaterials.