Preadhesion Laser Surface Treatment of Carbon Fiber Reinforced PEEK Composite

An excimer UV laser (193 nm) was used for preadhesion surface treatment of PEEK (polyetheretherketone) composite. This method presented an alternative to other limited and polluting conventional surface treatment methods. Experimental results indicated that laser preadhesion treatment significantly improved the shear and tensile adhesion strength of structural epoxy FM 300 2K bonded PEEK composite adherends compared with untreated and SiC blasted substrates. Best results were obtained with laser energies of 0.18 or 1 J/P cm.² Shear strength of laser-treated joints was improved by 450% compared with that of untreated PEEK composite and by 200% compared with SiC-blasted pretreatment at ambient and at extreme temperatures. An order of magnitude of improvement was found in the tensile strength-of laser-treated PEEK composite in a sandwich structure compared with non-treated or abraded sandwich joints. The mode of failure changed from adhesive to cohesive as the number of pulses or laser energy increased during treatment. The latter phenomenon was correlated with surface cleaning as revealed by XPS, with morphology changes as revealed by scanning electron microscopy, and by chemical modification as indicated by FTIR and XPS. The bulk of the PEEK composite adherend was not damaged by the laser irradiation during treatment as indicated by the identical flexural strength before and after laser treatment. It can be concluded that the excimer laser has a potential as a precise, clean and simple preadhesion surface treatment for PEEK composite.