An effective micro-arc oxidation (MAO) treatment on aluminum alloy for stronger bonding joint with carbon fiber composites

The micro-arc oxidation (MAO) treatment was used in this study to modify aluminum (Al) alloys to improve bond strength with carbon fiber reinforced polymer (CFRP). Various porous surfaces of Al alloy with better hardness, roughness and wetting were created. Void defects were reduced via using resin pre-coating (RPC) technique to guide high-viscosity epoxy into the holes, CNTs fiber bridging was constructed to improve bonding interface and epoxy adhesive layer. Combined treatments of "Na2SiO3 + KOH solution" MAO, RPC and introducing CNTs on Al alloy surface yielded 21.34 MPa, up to 156.1% increment over base strength. Original debonding failure on Al alloy surface was altered into dominant fiber tearing failure of CFRP composites, indicating the reinforced bond strength and stronger adhesive joint. MAO was the first try and proved as a feasible treatment for bond strength improvement, which could provide an alternative to manufacture high-performance Al-CFRP composites in industrial production.