A Topology-optimized Ultrastiff Mechanical Metamaterial Exhibiting Stiffness beyond Hashin-Shtrikman Upper Bound

The attached STL and STEP files are the lattices that correspond to a topology-optimized ultrastiff isotropic lattice structure whose stiffness exceeds the Hashin–Shtrikman upper (HSU) bound. This topology-optimized lattice, referred to as TO-SCO-HC, is provided at relative densities of 30% and 40% (STL file names: TO-SCO-HC_30RD and TO-SCO-HC_40RD). Due to the highly irregular surfaces of the topology-optimized lattices, CAD models were created by replacing these irregular regions to enable finite element simulations. The corresponding CAD versions are named SCO-HC lattices with relative densities of 30% and 40% (STEP file names: SCO-HC_30RD and SCO-HC_40RD). In addition, Figure 1 represents the new loading conditions used in Abaqus to generate ultrastiff topology optimized lattice.