Regeneration of interfacial bonding force of waste carbon fibers by light: Process demonstration and atomic level analysis

Although interest in recycling carbon fibers is rapidly growing, practical applications of recycled carbon fibers (rCFs) are limited owing to their poor wettability and adhesion. Surface modification of CFs was achieved through intense pulsed light (IPL) irradiation, which functionalizes surface of rCFs. Surface energy, chemical composition, morphology, and interfacial shear strength (IFSS) of rCFs before and after IPL irradiation were investigated. The rCF IPL-irradiated at 1,200 V improved both polar and dispersive components of surface energy, and the IFSS significantly increased by 2.93 times in relation to that of the pristine rCF and reached 95% of that of high-grade commercial CFs. We proposed a mechanism by which oxygen functional groups on the rCF surface enhance the molecular bonding force with HDPE, and the model was validated from molecular dynamics simulations. IPL irradiation is a rapid and effective surface treatment method that can be employed for the manufacture of rCF-reinforced composites.