Surface modification of carbon fibres via plasma-activated water for mitigating burnout risk from direct plasma treatment

Abstract This study presents a novel plasma jet discharge device designed to indirectly treat carbon fibre materials with plasma-activated water. This innovative method effectively mitigates issues related to carbon fibre conduction and combustion, which are common challenges encountered when directly modifying fibres using a plasma jet. Specifically, the atmospheric composition is adjusted to modulate the active particles in the liquid phase. The experimental results demonstrate that this technique significantly increases the surface wettability of carbon fibres without damaging their structure. Under the conditions of argon/oxygen cascade discharge, oxygen-containing substances generate ionomers that activate the water, which in turn introduces oxygen-containing groups (e.g., C−O, C=O, O−C=O) onto the carbon fibre surface. These groups catalyse monomer polymerisation on the material surface, which increases the wettability of the carbon fibres, as evidenced by a significant reduction in the water contact angle from 80.12° to 55.31°. This in turn improves the bonding strength with epoxy resin and slightly increases the monofilament strength. Furthermore, composites produced by this method exhibit 21% higher interlaminar shear strength than the untreated sample and an increased O/C ratio of up to 24.55%. In summary, these findings provide a valuable theoretical basis for enhancing the surface properties of carbon fibre composites through plasma–liquid interactions and open new possibilities for high-performance carbon fibre–resin matrix composites.