A numerical study on curved additive manufactured BCC lattice structures: low velocity impact behaviour

Nowadays use of sandwich structures in structural design is increasing, especially in transportation engineering fields, such as aeronautical and automotive. Sandwich structures are characterized by two thin layers (skins) with a thick, but light, core in the middle, for increased stiffness to bending. The improvement of additive manufacturing techniques opens the door to adopting lattice structures, very light and geometrically complex structures based on a repetitive element, as cores of sandwich structures. The advantages offered by these structures are related to the possibility to variate the structural behaviour by changing geometrical factors such as the array configuration, the unit cell shape or topology, and the relative density. The research presented in this paper is aimed at studying low velocity impact behaviour on curved additive manufactured body-centred cubic (BCC) lattice structures. These structures are characterized by a length L of 10 mm and are numerically designed by modifying the core unit cell topology. Starting from a linear configuration, sine-waved struts were introduced along the main diagonals of the cube, with a wavelength of 3L = 17.32 mm and an amplitude of 0.2 L. The curved shape is proposed with two different orientation. Moreover, the aim is to develop hybrid aluminium/composite structural solutions characterized by high energy absorption features for occupants passive safety purposes. Indeed, the components were able to absorb up to 76% of the initial impact energy with an indentation level lower than 3.7 mm. These structures feature low weight, due to a density of 0.715 g/cm3 for the whole component, and occupant protection in transportation. The direct metal laser sintering (DMLS) technology has been adopted by using the EOS M290 3D printer for metals.