Laser direct joining of carbon fiber reinforced plastic to zinc-coated steel

This study was performed to investigate the feasibilities, characteristics and mechanisms of dissimilar joints between carbon fiber reinforced plastics (CFRPs) and zinc-coated steel using a continuous wave (CW) diode laser. Tensile shear tests show that the high strength joint with about 3300 N could be produced. Many bubbles of sub-millimeter size inside the melted zone of CFRP at the cross sections of the joints were widely formed, and thin zinc-coated layer at the joint interface was partially fractured. Then, the melted plastic was filled closely to flow in the fractured zinc-coated layer, suggesting strong mechanical bonding. Furthermore, the joint was tightly bonded on atomic or molecular sized level between the melted plastic containing most carbon and nanometer thick zinc oxide film on the surface of zinc-coated layer, inducing strong possibility of physical and chemical bonding. It is consequently confirmed that a strong joint of CFRP to zinc-coated steel could be obtained by laser direct joining process.