Rate-dependent behaviour of additively manufactured topology optimised lattice structures

Lattice structures offer a wide range of tuneable qualities that cannot be achieved with bulk materials. While lattice structures offer a range of tuneable qualities, including isotropic properties achievable in bulk materials, the advent of additive manufacturing (AM) advances research in this domain. Although several studies have characterized the quasi-static mechanical properties of lattice structures, there is limited experimental data available on their rate-dependent behaviour. Additionally, most lattice structures are anisotropic, making them unsuitable for applications where loading directions are unknown. In this study, a topology-optimised unit cell with nearly perfect isotropic stiffness is investigated for its isotropic specific energy absorption under high strain rates. The dynamic response of the structure is evaluated using 3 different materials: CPTi, AlSi10Mg, and 316LSS, and both experimental and numerical methods are employed. The influence of topology and relative density on the mechanical properties of the structure are explored, and the specific energy absorption isotropy is determined by loading the lattices in various orientations numerically. This research fills the gap in knowledge regarding the rate-dependent behaviour of lattice structures and offers insight into the potential for isotropic lattice structures in engineering applications.