Enhanced tensile properties of truss lattice architectures with triply periodic minimal surface nodes

The periodic truss structures in mechanical metamaterials have received widespread attention, yet stress concentration at nodes promotes the failure of truss structures, in particular under tension load. Here we report that tensile properties (in particular, ductility) of truss structures can be remarkedly improved by replacing the surface at the node with a triply periodic minimal surface (TPMS) structure. The intrinsic stress concentration at nodes in truss lattice structure can be readily dissipated at TPMS-modified nodes and transferred to the connected ligaments, leading to the enhanced tensile ductility. Moreover, the efficacy of TPMS modification is found to be correlated with the node coordination number, where lattice structures with a high coordination number of nodes possess better property improvements. The role of TPMS nodes on stress transfer and deformation delocalization behaviors is well interpreted by the in-situ microstructural analyses as well as finite element modeling simulations.