Laser surface treatment for enhanced titanium to carbon fiber-reinforced polymer adhesion

The adhesion between carbon fiber-reinforced polymer (CFRP) and titanium parts can be improved by laser surface texturing before gluing them together. Here, a pulsed Nd:YAG laser was employed before bonding of the textured surfaces using an epoxy paste adhesive. To investigate the influence of the laser parameters, the roughness of the surfaces were characterized and correlated to the wettability, by measuring the contact angles of water droplets. Scanning electron microscope (SEM) characterization was also performed showing that under careful conditions, the fiber structure could be maintained. Tensile tests were performed to evaluate the influence of the laser treatment parameters on the joining efficiency. The lap-joint tensile strength tests presented the best results when the titanium surfaces were treated using 5.03 x 10(-3) J pulses and the CFRP sample treated with 5.03 x 10(-4) or 5.03 x 10(-3) J or even using a virginal CFRP surface. Using a virginal CFRP surface, the critical load of fiber delamination was increased and as a consequence the tensile strength attains the highest level of 8.2 MPa.