Multiscale topology optimization and experimental testing of metal lattice bridges produced by laser powder bed fusion

This work explores the synergy between metal additive manufacturing and topology optimization to enable lightweight structures with superior mechanical properties. The study first proposes a novel multi-scale topology optimization methodology to generate lattice-embedded structures, and applies it to the design of a bridge-like part under three-point bending. Four designs are generated, spanning macroscale volume fractions from 15% to 30% to explore mass–stiffness trade-offs. Each design is manufactured four times in a high strength aluminum alloy using laser powder bed fusion. Although pragmatic industrial examples exist, to the authors’ knowledge, this is the first reported study in which topology-optimized, lattice-embedded metal structures were successfully fabricated. Experimental three-point bending tests assess printing quality, the force–displacement response (linear and nonlinear) and failure behavior. The results show excellent print fidelity, low variability, and close agreement between measured and numerical volume fractions. While linear stiffness does not match numerical predictions, the experiments reveal highly tunable crack propagation. In particular, the sequential failure of unit cells leads to stable energy absorption and placement of solid regions is shown to cause direction-changing crack paths. The findings highlight the potential of jointly optimizing lattice geometry and solid–lattice distribution to tailor mechanical response and failure modes in additively manufactured structures.