Robustness of stress focusing in soft lattices under topology-switching deformation

Abstract: Recent developments in topological mechanics have demonstrated the ability of Maxwell lattices to effectively focus stress along domain walls between differently polarized domains. The focusing ability can be exploited to protect the lattice bulk from accidental stress concentration -- and eventually onset and propagation of fracture -- at structural hot spots such as defects and cracks. A recent study has revisited the problem for structural lattices featuring non-ideal hinges, showing that the focusing remains robust, albeit diluted in strength. Realizing that the problem of domain wall localization has been traditionally framed in the context of linear elasticity, in this work we extend the study to the realm of soft structures undergoing nonlinear finite deformation. Through experiments performed on silicone hyperelastic prototypes, we assess and quantify the robustness of the phenomenon against the macroscopic shape changes induced by large deformation, with special attention to deformation levels that alter the topology of the bulk, lifting the topological protection. Furthermore, we identify a simple geometric indicator for this transition.