Effect of grain size on the optimal architecture of electrodeposited metal/polymer microtrusses

Nanocrystalline microtruss materials are novel cellular hybrids of metal and polymer produced by electrodepositing thin coatings of nanocrystalline metal over rapid prototyped polymer preforms. This study develops an optimisation method for the architectural design of electrodeposited metal/polymer composite microtrusses used as cores in sandwich beams. For an optimally designed structure employing conventional polycrystalline nickel, a direct substitution of nanocrystalline nickel will improve structural performance; however, it is likely that the structure will also become significantly sub-optimal. Achieving optimal design with nanocrystalline nickel entails large geometric changes from the conventional polycrystalline case. The same applies if the polymer preform is removed after electrodeposition. The strong connection between optimal architecture and grain size was therefore examined for the limiting cases of polymer-filled and hollow microtrusses. It was found that grain size reduction was more important than polymer preform removal such that grain size effects dominate over the majority of microtruss design space.