Laser direct joining of carbon fiber reinforced plastic to aluminum alloy

Laser direct joining of carbon fiber reinforced plastic (CFRP) to aluminum alloy was performed using a high quality continuous wave diode laser with a line-shaped beam. The tensile shear test results demonstrated that a strong lap joint with about 3000 N could be produced between CFRP (of 3 mm thickness and 20 mm width) and aluminum alloy (of 2 mm thickness and 30 mm width). The joints fractured along the joint interface or in the melted zone of CFRP. It was observed from the cross sections of the joints that many bubbles of submillimeter size were irregularly formed in the wide and shallow melted zone of the CFRP. Moreover, melted polyamide plastic was tightly bonded on atomic or molecular sized level through nanometer thick aluminum oxide film (κ-Al2O3) existing on aluminum alloy surface, suggesting high possibility of chemical or physical bonding between CFRP and metal. Consequently, it was confirmed that a strong lap joint of CFRP to aluminum alloy could be produced by direct irradiation of a laser beam.