2020 Volume 46 Issue 4 Pages 143-149
This study investigated the effect of vacuum ultraviolet (VUV) light irradiation on the thermal fusion bonding strength of carbon fiber/thermosetting polyimide composite laminates (CF/PI) using a thermoplastic polyimide (TPI) film as a hot-melt adhesive. The adherend (CF/PI) and/or adhesive (TPI) surfaces were irradiated by the VUV light (72nm) for 4 min in a low oxygen atmosphere (0.2±0.1%), followed by the thermal bonding of two CF/PI specimens with TPI film adhesive under 320ºC. The bonding shear strength was observed to be improved considerably from 18.6 MPa to 36.2 MPa through the VUV light irradiation process. In addition, the fracture behavior changed from an interface fracture mode into a cohesive or adherend fracture mode. To elucidate the surface modification, chemical analyses of the CF/PI and TPI surfaces were carried out based on the X-ray photoelectron spectroscopy. Experimental results revealed that carbonyl and hydroxyl groups were introduced on the CF/PI and TPI surfaces by VUV light irradiation. It was suggested that these functional groups may contribute to improve the bonding shear strength.
