Increasing adhesive bonding of carbon fiber reinforced thermoplastic matrix by laser surface treatment

In this study, laser surface treatment of CFRP made of PPS thermoplastic matrix by means of Q-switched Yb:YAG fiber laser is investigated with the aim to improve CFRP adhesive bonding. Two set of experimental tests were developed. In the first, laser treatments were executed fixing the average power (Pa) and changing: the pulse power, the scanning speed, the hatch distance, and the scanning strategy. These tests were performed to individuate the laser-material interaction mechanisms and the process window. The treated surfaces were investigated using optical microscopy. It was found that the treatment is able to remove the outer layer of the matrix up to the exposure of underlying reinforcement. However, depending to the released energy, incomplete cleaning or excessive damage may occur. Then, the operating window was experimentally determined. In the second experimental tests, single lap shear tests were performed on samples treated under the most promising process conditions, to verify the laser treatment effectiveness. It was found that the laser treatment, compared to the untreated samples, is able to increase the apparent shear strength up to three times.