Oxidation of copper fiber surface to improve fracture toughness of Cu/epoxy composite

Controlled oxidation treatments are applied for the first time to the surface of ductile Cu fibers which are used in epoxy matrix composites. The oxidation treatments produce either “A-nanoleaves” or black or red oxide “B-nanoleaves” with various nanoscale morphologies. Single fiber pullout (SFP) tests were performed on the oxidized fibers to evaluate how friction produced by their engineered surfaces will affect composite toughness. A highly cross-linked epoxy (HCLE) showed excellent formation of individual asperities which provided a significant increase in pullout work with black oxide B-nanoleaves. A standard epoxy (SE) with lesser cross-linking showed no asperities but rather a general roughness which also produced a significant increase in pullout work with black oxide B-nanoleaves. It was found that the standard acetone pre-treatment which is applied to remove polar impurities before oxidation can be shortened substantially from the standard 20 min to 5 min.