A novel parameter to tailor the properties of prismatic lattice materials

Lattice materials are extremely efficient in combining high stiffness and strength at low densities. Their architecture is a periodic assembly of bars, which, in most cases, all have the same length and cross-section. This is, however, suboptimal since the level of stress is not the same in all bars. To take these variations into account, we propose to design prismatic lattices with two different bar thicknesses. The ratio of these two thicknesses introduces a new parameter in the design of lattices. Analytical expressions are developed to capture the effect of this new parameter on the elastic modulus, failure mode and compressive strength of hexagonal and triangular lattices. This analytical work is then validated by finite element simulations and experiments performed on polymer lattices fabricated by additive manufacturing. This new parameter offers two advantages in the design of prismatic lattices. First, the thickness ratio can be used to vary the properties of a lattice without changing its relative density. Second, it allows to stiffen and strengthen the lattice along a specific loading direction and therefore, controls the degree of anisotropy. This work opens new possibilities to tailor the mechanical properties of prismatic lattices, and facilitates the creation of new materials by design.