Improvement of bonding strength of scarf-bonded carbon fibre/epoxy laminates by Nd:YAG laser surface activation

In this work bonding surface activation for scarfed repair bonds on carbon fibre reinforced plastics is investigated. For activation and cleaning of a scarfed bond between two cured laminates different Nd:YAG lasers were employed, in order to remove resin to enable embedding of fibres in the adhesive film and to improve wetting and bonding between the fibres and the adhesive. Microscopic investigation shows varying degrees of fibre stripping and oxidation. Latter enables covalent bonds between fibres and epoxy adhesive leading to a full recovery of the parts mechanical properties demonstrated in tensile tests. Measurement of acoustic emission during tensile tests gave further insight on the quality of the joint. Results from other activation parameters indicate optimisation steps to further improve the bonding strength and thus reducing repair area and costs significantly.