Energy absorption of 3D printed stochastic lattice structures under impact loading – design parameters, manufacturing, and testing

Abstract The Voronoi lattice structure is one of the stochastically distributed strut-based lattice structures. In contrast to non-stochastic lattice structures, this means that the geometric structure is based on a random distribution of struts based on the Voronoi algorithm. In distinction to conventional open-pore foams, which also have a stochastic distribution of pores, the additive manufacturing of such structures offers the advantage of being able to vary the design parameters locally. There are two main design parameters defining the density and thus potentially influencing the mechanical characteristics of this structure: the strut diameter and the density of the starting points of the Voronoi algorithm resulting in a density of struts. This quantifies the influence of these design parameters on the energy absorption capability of Voronoi structures. The structures are manufactured from polyamide 12 using the SLS process and are tested at impact speeds of 5 m/s showing promising potential for energy absorption applications. To furthermore improve these characteristics graded lattice structures are also investigated at which both the density of the structure and the diameter of the struts are varied. A Design of Experiments (DoE) approach was used to proof the results statistically. It was found that structures with a density of 25% have the highest specific energy absorption (SEA) value of the investigated specimens. In addition, the combination of a small strut diameter and a high number of struts should be selected for the application of energy absorption. Grading of the structures can not only reduce the first stress peak after impact but also decreases overall performance. In general, there is room for improvement in terms of energy absorption capabilities of these structures.