Double-wall ceramic nanolattices: Increased stiffness and recoverability by design

[Display omitted] •Introduction of a new class of mechanical metamaterials, the double-wall lattices.•Alumina double-wall nanolattices with densities from 4.89 to 19.91 kg m−3 are tested in situ.•Double-wall nanolattices exhibit high specific stiffness and are recoverable.•Reduced trade-off between stiffness and recoverability of ceramic nanolattices. Lightweight ceramic nanolattices exhibiting high stiffness and good recoverability are obtained by leveraging base material size effects in combination with smart structural design. Here, the double-wall tube (DWT) lattice architecture is introduced to increase the stiffness of brittle nanolattices, while maintaining their recoverability. The DWT architecture consists of two nested simple-cubic hollow-truss nanolattices. The superposition of two nanolattices leads to a reduced wall thickness for a given relative density thereby preventing the built-up of large stresses at the cell wall level when crushing the lattices. In this work, DWT alumina nanolattices are fabricated and compressed in situ to demonstrate the improvement in recoverability with decreasing alumina wall thickness. The results from finite element simulations reveal that double-wall architectures are up to two times stiffer than their single wall counterparts of equal mass, suggesting that superior recoverability (thinner ceramic coatings) coupled with enhanced stiffness can be achieved. The DWT lattice is proposed as a new architecture to expand the design space of highly recoverable brittle nanolattices. The new double-wall design concept is expected to provide an efficient tool for improving the mechanical performance of shell-nanolattices in general including triply-periodic minimal surfaces.