Dependence of the mechanical properties of pentamode materials on the lattice microstructure

Pentamode materials consist of diamond-like lattices featuring five soft modes of deformation. Such materials have been proposed for transformation acoustics and elastomechanical cloak, but their potential in different engineering fields is still only partially explored. One characteristic in particular appears very appealing in this type of lattices: the dependency of the mechanical properties of the structure on the microstructure of the lattice rather than on the chemical nature of the employed materials. This characteristic implies the possibility to easily tune the effective mechanical properties of pentamode lattices to comply with the specific demands of the material at the meso- and macro-scales, with the aim of designing novel engineering devices, such as, e.g., innovative seismic isolators. The present work includes numerical and experimental studies investigating the dependence of the mechanical properties of pentamode materials on aspect parameters at the microscopic and macroscopic scales. It is shown that such materials exhibit elastic and post-elastic responses similar to those of elastomeric bearings alternating rigid layers and soft rubber layers.