Size effects in lattice structures

Lattice structures within thin-walled regions of modern lightweight structural components contain only a few unit cells (range ∼1–6). The mechanical behaviour of such lattices is sensitive to the specimen-to-cell size ratio (L*/d), and thus, size effects require a better understanding. To elucidate these size effects, Nimonic 263 BCC lattices manufactured via laser powder bed fusion additive manufacturing, with L*/d = 1–10, were investigated. Compressive behaviour, together with post-deformation EBSD-based Kernel Average Misorientation (KAM) analysis, was validated using Finite Element Analysis (FEA). Critical analyses reveal that deformation is dictated by the relative load-bearing capacity of distinct nodal junctions, resulting in a yield strength plateau at L*/d ≈ 4, beyond which a size-independent behaviour. Based on these insights, a “nodal constraint model” is proposed that links the load-bearing node fraction to the observed size effects in bending-dominated lattices. Further analysis showed that even published literature data are in good agreement with the proposed model.