Gamma-ray irradiation to achieve high tensile performance of unidirectional CNT yarn laminates

Abstract

Continuous carbon nanotube (CNT) yarn fabricated from a floating catalyst chemical vapor deposition (FCCVD) method is treated under gamma-ray irradiation to enhance the mechanical properties of the CNT yarn and its unidirectional composite laminates. Gammy-ray doses varying from 50 kGy to 1200 kGy are used to irradiate CNT yarns and their microstructures, tensile properties and surface characterizations are studied. The graphitic structure change is not clear from the transmission electron microscopy, however, the specific tensile strength and modulus of yarn vary slightly within 10 % as the dose increased. This modulus trend coincides with mesoscopic distinct element modeling (mDEM) simulation results. Surface characterization shows additional oxygen functional groups and smaller contact angles after irradiation. Interestingly, the specific tensile properties of composite laminates also increase relative to the yarns, and the unidirectional laminate from CNT yarn treated with the optimal dose of 700 kGy achieves specific strength and modulus as high as 1.89 GPa/gcm−3 and 258 GPa/gcm−3, respectively, which are 30.9 % and 37 % increases compared to the control laminate. The results indicate that radiation-induced crosslinking among the CNTs and the formation of surface-active sites leads to enhanced load transfer in the yarns and promote CNT/resin interfacial bonding.