Effects of surface laser treatment on direct co-bonding strength of CFRP laminates

Laser surface treatment is a promising technique to increase the adhesive strength of carbon fibres reinforced plastics joints. In this technique, the laser beam is adopted to remove the outer matrix layer up to the expose the underlying reinforcement. This study deals on the effect of laser treatment on the joint strength of CFRP laminate obtained by direct co-bonding. To this aim, laser treatments at different process conditions were performed on autoclave cured CFRP, adopting a pulsed Yb:YAG fiber laser. The obtained surfaces were characterized by microscopy. Single lap joints were obtained by infusion techniques by superposition of fresh laminates and laser treated laminates without any kind of adhesive. Untreated and sandpaper treated samples were adopted as reference specimens. After joints consolidation, mechanical tests were carried out; apparent shear strength was measured and post mortem analysis was performed. The results show that laser treatments allow the doubling of the apparent shear strength.