Ti–6Al–4V hybrid-strut lattice metamaterials: A design strategy for improved performance

Metal hollow-strut lattices manipulate the strut and node sections to achieve higher strength. Although these metamaterials have recently surpassed the structural efficiency of conventional solid-strut lattices of comparable density and topology, they often observe localised yielding and fragmentation through the nodes that limit their structural efficiency. To quantify the effect of this localised failure and to develop mitigating strategies, we have integrated solid and hollow strut and node sections in singular Ti–6Al–4V simple cubic hybrid-strut lattices for a deployable relative density range of 15–30%. Fabricated through laser powder bed fusion these hybrid-strut lattices are stronger (32%), stiffer (15%), and tougher (65%) than solid-strut lattices of equivalent density. Interestingly, the metamaterials with hollow beams can transition from a bending-dominated to a stretch-dominated deformation response with increasing density, while the lattices with solid beams only observed a uniformly stretch-dominated deformation response. The combination of solid and hollow strut and node sections in the hybrid-strut lattice establishes a simple yet effective strategy to enhance structural efficiency and control of failure response without increasing density or manipulating unit cell topology.