Comparative study of processing environments in fiber laser texturing of CFRP for enhanced adhesive bonding strength

Laser surface texturing of carbon fiber reinforced polymer (CFRP) surfaces serves as a viable option for achieving improved surface preparation for adhesive bonding; however, CFRP surfaces may retain defects that can affect the service performance of the joint. In the present study, an investigation was carried out to reduce these defects in the fabricated textures. A nanosecond fiber laser was used to texture the CFRP surface under open-air, water mist-assisted, and underwater processing conditions for controlled fiber exposure on CFRP sheets. A grid-based pattern was fabricated on the CFRP surface under focused (0 mm) and defocused (10 mm) conditions in different processing environments, and the resulting surface morphology was characterized. The results suggest that defocused laser processing under water mist-assisted and underwater conditions provided a more favorable approach for fiber-laser texturing of CFRP. The preservation of intact fibers, along with the increased proportion of polar functional groups, resulted in enhanced adhesive bonding, with lap shear strengths of 21.5 MPa and 21.1 MPa for the defocused water-mist-assisted and underwater conditions, respectively, compared with 10.2 MPa for the untextured surface. The study demonstrates the potential of these proposed texturing approaches as a surface preparation technique for adhesive bonding of CFRP.