Design and manufacture of hybrid metal composite structures using functional tooling made by additive manufacturing

This paper presents a novel manufacturing technique for complex-shaped, hybrid metal composite structures leveraging the design freedom of additive manufacturing (AM). The key novelty of this research is an approach for an autoclave-suitable and removable tooling, which consists of a 3D-printed functional shell and a structural filler material. In this process, a layup shell is produced with AM and filled with a temperature-resistant curing support to form a removable inner tooling. The functional shell has integrated design features for the positioning and the fixation of metallic interface elements and is removed after curing through integrated breaking lines. The feasibility of this manufacturing technique is demonstrated by fabricating a novel lightweight structure for the hydraulic quadruped (HyQ) robot. Selective laser sintering (SLS) was used to produce the functional shell tooling. Titanium interface elements made via selective laser melting (SLM) were assembled to the shell and co-cured to carbon fiber using an autoclave prepreg process. The resulting multi-material structure was tested in ultimate strength and successfully operated on the HyQ robot. Weight savings of 55% compared to a reference design and the mechanical viability of the multi-material structure indicate that the proposed manufacturing technique is appropriate for individualized hybrid composite structures with complex geometries.