Controlled deformation of metallic hollow octet-truss lattice structures

Metallic hollow octet-truss lattice structures combine strength and lightweight properties with a notable post-yield plateau under large compressive strain. This research develops a systematic beam theory-based analytical model, incorporating shear effects and potential structural instabilities, to understand and predict the post-yield response of hollow octet-truss lattice structures under large compressive strain. Finite element modelling (FEM) at the lattice level provides plastic strain equivalent (PEEQ) data to embed the plastic properties of the base material into the analytical model. To validate the model, uniform hollow octet-truss SS316L lattice samples are fabricated using powder bed fusion (PBF) techniques. Findings indicate that inelastic local shell buckling and hollow joints in low-density hollow octet-trusses enhance stable deformation and a long post-yield plateau. With the proposed method, controllable deformation of hollow octet-truss lattice can be achieved via accurate prediction of stress-strain curve and deformation mechanism under large compressive strain. By further conducting parametric study, the proposed methodology can be regarded as an initial point to enhance the programmability of lattice structure design. The proposed methodology can also be extended to other types of hollow lattice structures. These insights pave the way for innovative applications in aerospace, biomedical, and other engineering fields.