Mechanical and energy absorption characteristics of additively manufactured functionally graded sheet lattice structures with minimal surfaces

Functionally graded (FG) lattice structures have attracted attention for their potential application in lightweighting and energy absorption. In this study, functionally graded sheet (FGS) structures with primitive (P) and gyroid (G) minimal surfaces were fabricated by selective laser melting (SLM) using Ti-6Al-4V powder. The mechanical properties, deformation behavior, and energy absorption performance of uniform sheet (US) and FGS lattice structures were systematically investigated using compression tests and the finite element method (FEM). The FGS structures were found to eliminate abrupt shear failure and to exhibit the predictable layer-by-layer deformation accompanied by sub-layer collapse. The cumulative energy absorption per unit volume of FGS samples increased as a power of strain function throughout the compression process, while the US samples exhibited a linear relationship, thus resulting in an excellent energy absorption capability for FGS structures. The energy absorption of FGS samples was higher than for US samples by approximately 60%. In addition, the results of FEM with the Johnson-Cook models demonstrated a high capability for predicting the deformation behaviors as well as mechanical properties (especially in terms of yield strength, compressive strength and energy absorption) of lattice structures. which can be used to provide guidance on selecting a lattice structure to meet multifunctional demands.