Stiffness characterization of curved structures made of lattice materials: Additive manufacturing, measurements and numerical estimations

Most experimental studies that characterize the mechanical properties of lattice structures have used samples with straight macro-shapes, such as cylinders or prisms. However, real-world applications often demand more complex geometries. As a first step towards addressing this, lattice structures with curved macro-shapes were designed with various cellular topologies and arrangements and subjected to transverse loads to evaluate their effective stiffness. This evaluation allows the characterization of the effect of the topology and arrangement on the stiffness of the latticed curved beams; obtaining a thorough understanding of the role of various design parameters to tune the effective stiffness of lattice structures. Load-displacement curves were obtained using laboratory tests, homogenization techniques, and finite element analysis. Experimental tests were done on two groups of additively manufactured samples subjected transversally at the midpoint. We analyzed the effective transverse stiffness of linearly arranged cellular topologies (square, hexagonal, and re-entrant) used to form curved beams. It was found that the hexagonal lattice had a 9.80 N/mm stiffness that was approximately 67% stiffer than the softest, which was the square lattice oriented at 45°. Then, each topology was modified for radial arrangement for further study on how conformal arrangements influence the effective transverse stiffness. The square lattice in a conformal (radial) arrangement had a 20.68 N/mm stiffness, that was approximately 130% stiffer than its linear arrangement counterpart.