3D Plate‐Lattices: An Emerging Class of Low‐Density Metamaterial Exhibiting Optimal Isotropic Stiffness

In lightweight engineering, there is a constant quest for low‐density materials featuring high mass‐specific stiffness and strength. Additively‐manufactured metamaterials are particularly promising candidates as the controlled introduction of porosity allows for tailoring their density while activating strengthening size‐effects at the nano‐ and microstructural level. Here, plate‐lattices are conceived by placing plates along the closest‐packed planes of crystal structures. Based on theoretical analysis, a general design map is developed for elastically isotropic plate‐lattices of cubic symmetry. In addition to validating the design map, detailed computational analysis reveals that there even exist plate‐lattice compositions that provide nearly isotropic yield strength together with elastic isotropy. The most striking feature of plate‐lattices is that their stiffness and yield strength are within a few percent of the theoretical limits for isotropic porous solids. This implies that the stiffness of isotropic plate‐lattices is up to three times higher than that of the stiffest truss‐lattices of equal mass. This stiffness advantage is also confirmed by experiments on truss‐ and plate‐lattice specimens fabricated through direct laser writing. Due to their porous internal structure, the potential impact of the new metamaterials reported here goes beyond lightweight engineering, including applications for heat‐exchange, thermal insulation, acoustics, and biomedical engineering.