Enhancing interfacial bonding and mechanical properties of CF/EP composites through low-temperature jet plasma treatment

Carbon fiber reinforced epoxy (CF/EP) composites are widely employed in aerospace, automotive, and maritime industries. However, the inherently smooth surface and low chemical reactivity of carbon fibers compromise the interfacial bonding with epoxy resin. This study examines the effect of low-temperature jet plasma treatment at various processing speeds (25, 50, 100, and 200 mm/s) on the surface characteristics of carbon fibers and the mechanical performance of CF/EP composites. A treatment rate of 50 mm/s was found to optimally enhance fiber surface roughness and promote the formation of -C=O functional groups—evidenced by a decrease in carbon content from 75.51 % to 73.27 % and an increase in oxygen content from 24.49 % to 26.73 %. Consequently, composites fabricated under these conditions exhibited notable improvements in bending strength (522.28 MPa, +19.23 %), bending modulus (33.22 GPa, +50.38 %), tensile strength (610.62 MPa, +40.35 %), and tensile modulus (27.94 GPa, +38.59 %). Scanning electron microscopy further confirmed enhanced interfacial bonding through a reduction in voids. This concise study provides experimental evidence for optimizing carbon fiber surface treatments to achieve superior composite performance.