Intelligent Design of Cellular Solids for Impact Mitigation

Disordered networks, comprised of random arrangements of bonds and nodes, offer degrees of mechanical tunability not accessible to periodic systems. These networks have emerged as the basis of a new class of metamaterials allowing for precise control over density (ρ), bulk (K), shear (μ) modulus, and Poisson’s ratio (ν). Here, we demonstrate bond pruning and global node position optimization as effective routes for designing cellular materials with isotropic auxetic properties, and for independently controlling μ and K. We show how bond pruning controls ρ, μ and K. Node position optimization allows for the tunability of ν from ∼0.3 to −0.5, control over two orders of magnitude of K with almost no change to μ and minimal change in foam density. We use multi-resin 3D-printing to extract the 2D and 3D disordered networks out of the simulation box and systematically study how the tunability of elastic constants affect their dynamic deformation behavior. We explore how node bending stiffness can affect global elastic properties and quantify how it affects the range of elastic tunability. This study demonstrates the power of top-down design of disordered network metamaterials and how such level of tunabililty can affect the next generation of materials for impact mitigation.