Investigating the impact of laser treatment on fracture modes and strength of CFRP/AL 6061 single lap joint

The mechanical performance of the adhesively bonded joint can be improved by enhancing the surface properties with laser. The laser treatment is fast, safe and practicable method for a wide range of materials including carbon fiber reinforced polymers (CFRP). In the current research, different power to speed combinations of a CO2 laser beam was used to modify the surface of the CFRP side of a CFRP/AL6061-T6 lap joint specimens prior to adhesive bonding. The adhesively bonded single lap joint (SLJ) specimens were tested in tension to investigate the influence of the laser treatment on shear strength, elongation and fracture mode. The roughness of the treated surfaces was measured using a non-contact profilometer and post failure modes were identified using optical microscopy and scanning electron microscopy (SEM). The results show a noticeable impact of the power to speed ratio of the laser beam on the roughness of the prepared surfaces. Moreover, a significant joint strength increase of 62% was measured over the untreated joint when the laser power and speed were 50 watts and 100 m/s respectively. An extended adhesive curing time also increased the joint strength. These changes in joint strength were accompanied by a change in the failure mode.