Investigation of graded metallic lattice structures by thick film electroplating of additively manufactured polymer lattices

Additive manufacturing (AM) of metallic lattice structures enables lightweight, high-performance components for structural and multifunctional applications. However, direct metal AM processes are costly and resource-intensive. This study investigates a hybrid approach that combines the geometric flexibility of polymer AM with the mechanical performance of electroplated metals. Polymer lattice templates with fine features were fabricated via stereolithography and subsequently coated with thick copper layers through a 48-h electroplating process. The resulting hybrid structures achieved a copper mass fraction exceeding 98% and exhibited a relative density of 18.9%, comparable to fully metallic lattice materials. Mechanical testing under uniaxial compression revealed substantial improvements in structural performance: while absolute stiffness and strength increased by up to 500 times compared to the uncoated polymer lattice, the relative density also increased significantly. To account for this, the relative effective modulus, defined as the ratio of relative modulus to relative density, was evaluated, demonstrating a 30-fold improvement through metallization. Failure analysis revealed stretch-dominated deformation and brittle collapse modes, closely resembling those observed in hollow metallic lattices. These results highlight the potential of thick-film electroplating as a scalable and versatile route to fabricate mechanically efficient, predominantly metallic lattice structures. This approach paves the way for multifunctional applications in lightweight and energy-absorbing systems.