Improving adhesive performance of CFRP joints through combined laser texturing and resin pre-coating

Surface preparation of adherends remains a critical step in the fabrication of high-performance and reliable bonded joints. Among the recently investigated techniques for structural bonding of CFRPs, laser ablation of the polymer matrix enables the formation of a regular dimpled texture with locally exposed carbon fibers. However, the high viscosity of structural adhesives often limits their ability to effectively wet the fiber surfaces within the dimples, potentially reducing the mechanical interlocking at the interface. This study explores a synergistic surface treatment method combining laser texturing with a resin pre-coating (RPC) step, where the textured surfaces are impregnated with a diluted uncured epoxy solution. The significantly reduced viscosity of the solution enables enhanced penetration into the laser-induced cavities, thereby improving the subsequent interfacial adhesion through increased mechanical interlocking upon curing of the structural adhesive. The method was evaluated on End Notched Flexure (ENF) specimens, revealing an average load increase of approximately 25% compared to samples treated with laser texturing alone. The results demonstrate the potential of this combined approach to further enhance the effectiveness of laser-based surface pre-treatment methods for structural bonding of CFRPs in industrial applications.