Abstract

In this talk I will focus on the failure properties of metallic foams and the mechanics and charge-induced actuation of metal and graphene nanofoams. The fracture strength of metal foams depends sensitively on the properties of the constituent material as well as the cellular architecture. A change in microscopic properties carries over to the macroscopic scale through an alteration of the mesoscopic damage and fracture mechanisms. To study these dependencies we have developed a multiscale modelling framework that takes these ingredients into account. The influence of the relative density, material strain hardening, cell shape anisotropy, structural randomness and specimen size on the cell wall damage behavior and overall fracture response is analyzed in detail. Finally, all material and architectural effects are summarized in a strength versus ductility graph, identifying trends for improved design of metallic foams. Recent experimental studies have shown that metallic and graphene nanofoams can undergo dimensional changes when a potential difference is applied in an electrochemical environment. The primary actuation mechanism is the electric-double layer charging of the internal surface. To account for the excess charge we have developed an atomistic model that is informed by ab-initio density functional theory calculations. To make a scale transition to the continuum scale, we propose a surface layer model that is informed by the atomistic simulations. We study the charge-induced actuation strain and work-density of ordered and disordered nanoporous gold and graphene architectures. The differences between the ordered and disordered structures are critically addressed.