A design strategy to enhance the mechanical response of diamond-based lattice structures produced by laser powder bed fusion

Abstract

Lattice structures have been mostly used and studied considering one unit cell with a fixed build orientation. As a consequence, these meta-materials exhibit total failures when loaded over the yield stress, resulting in localized shear bands. In this article, a design strategy to enhance the mechanical behaviour of diamond-based lattice structures is proposed. The methodology is based on the rotation of layers of unit cells around a specific axis, to generate meta-coherent twin boundaries in the lattice, that can harden the meta-material. The proposed strategy is ideal for laser powder bed fusion of diamond-based lattices as all struts in the lattice keep the same orientation hence yielding repeatable and predicable lattice quality whilst still enabling significant local variations in mechanical performance. The new design strategy has been compared with classic diamond-based lattices both numerically and experimentally. The results in both cases demonstrated the value of incorporating meta-twin boundaries in the structure to increase the mechanical response while also reducing the extent of the localized shear bands.