Performance and mechanisms of ultraviolet laser ablation of plain-woven CFRP composites

Abstract

Plain-woven carbon-fiber-reinforced-polymer (CFRP) composites prove advantageous in designing and manufacturing aeronautic and aerospace structures due to their excellent mechanical properties. Their harsh service environment usually leads to aircraft surface pits, scratches, and other types of defects, which result in internal damages that reduce their strength, influencing their safety and reliability. With laser-controlled ablation, surface damage removal was implemented. However, the multiscale characteristics of plain-woven CFRP (macroscopic plain-woven textiles, mesoscopic fiber clusters, together with microscopic fiber and epoxy resin) lead to complex thermal–mechanical ablation action, prone to secondary surface damages and resin residue. Aiming at the requirement of high-performance removal of the damaged zone, a comprehensive investigation of the influence of laser ablation strategies, including the wavelength, defocus distance, scanning speed, hatch distance, scanning passes, etc., on generating morphologies was conducted. Results identified that the severe anisotropy of plain-woven CFRP gained a wide heat-affected zone (HAZ), which was restrained by adopting an ultraviolet (UV) laser ablation means. A high-quality laser ablation zone without visible resin residue and broken carbon fiber has been presented by one-pass laser ablation when a particular scarfing conditions combination was used. Meanwhile, a depth-controlled surface-forming approach was gained, accompanied by multiple laser scanning. Subsequently, a hybrid laser treatment strategy was provided for characteristic structure generation, and a novel stepwise structure was constructed for verification.