Effect of surface preparation on adhesive bonding of CFRP compression molding laminates

Composite structures are increasingly being used across various industries to promote structural lightweighting but also because of their excellent fatigue and corrosion resistance. To further minimize weight while preserving these benefits, adhesive bonding is now widely used to join advanced composite materials. However, effective surface pretreatments are essential to ensure suitable joint mechanical properties, including strength, fracture toughness, and long-term durability. The present study investigates viable surface preparation methods for a carbon fiber reinforced composite obtained through compression molding. Both standard mechanical abrasion and advanced ultrashort UV-laser treatment were evaluated. The effect of surface modification on surface morphology was evaluated using Scanning Electron Microscopy (SEM), while the corresponding modification of surface chemistry was determined using Energy Dispersive X-ray Spectroscopy (EDS). The combined results allowed us to judge the ability of the proposed strategies to modify surface morphology and remove post-processing contamination, primarily silicon-based. Besides, displacement-controlled tensile tests were conducted on adhesive-bonded single-lap joints to assess joint strength. The results show that UV laser ablation effectively removes contaminants on the matrix material without damaging the carbon fibers, improving adhesive joint shear strength compared to sanded specimens.