Shear strength of bonded joints of carbon fiber reinforced plastic (CFRP) laminates enhanced by a two-step laser surface treatment

The apparent shear strength of single-lap bonded joints of carbon fiber reinforced plastic (CFRP) can be enhanced by laser surface treatment. In this work, a two-step laser surface treatment was used to improve the single-lap bonded joint performance of CFRP-laminates. STEP-1, the resin at the outer surface of laminates was completely removed by an optimal laser etching process to provide neat carbon fiber fabric. STEP-2, the as-obtained exposed carbon fiber fabric was further irradiated to produce a series of mini-grooves on its surface. Laser scanning parameters, i.e., spot distance, scanning angles, groove distance and patterns, were investigated to analyze their effects on the morphologies of generated grooves. Single-lap shear tests were also carried out to assess the mechanical performance of these laser processing bonded joints. Experimental results indicated that crossed grooves significantly enhanced the shear strength of the CFRP-laminates. Failure morphologies of shear tests were observed to analyze the strengthening mechanism of grooved-CFRP by laser surface treatment. Using optimal processing parameters during laser surface treatment, the apparent shear strength of single-lap bonded joints of CFRP-laminates reached 18.58 MPa, implying a 40.8% enhancement compared with smooth laminates.