Micro/nano dual-scale porous surface structure of the Al alloys and improvement on the joint strength with carbon fiber reinforced PA 6 thermoplastic

Improving the interfacial bonding strength of the Al/CFRTP hybrid composites is beneficial for its application in lightweight automotive technology. This study fabricated the micro/nano dual-scale porous surface structures of the Al alloy by the low-cost and effective oxalic acid anodizing to improve the interlocking interface structure. The effects of current density and oxidation time of the anodic oxidation on the shear strength of the Al/PA 6 CFRTP hybrid composite joints were investigated. The results showed that with the increase of the oxidation current density and time, the nanopore diameter, porosity, wettability, and oxide film thickness were significantly improved. The shear strength of the Al/CFRTP PA 6 joints was as high as 23.7 MPa. The micro-scale pits (average size 6 μm) produced by the NaOH treatment and the nano-scale porous structure (16–106 nm) induced by anodizing enhanced the adhesion area and anchoring effect between the Al alloy and PA 6 resin. Thus, the synergistic improvement in the interfacial bonding strength was exhibited.