Novel Design of Carbon Fiber-matrix Interphase in CFRP

－Reinforcement of the Interphase between Carbon fiber and Matrix Using a CNT Coating Method－

Abstract

A new method to install carbon nanotubes（CNTs）as a secondary reinforcement at the fiber-matrix interphase in carbon fiber reinforced plastics（CFRPs）has been developed. This new approach delivers CNTs by coating carbon fibers（CFs）with CNTs which are subsequently impregnated with an epoxy resin. In this method, a cationic polymer treatment of the CNTs was used to create a stable dispersion of the CNTs in water, achieving a uniform coating of CNTs to the fiber surface. Using the CNT-coated CF and untreated CF as a control, unidirectional CF/epoxy composites were fabricated using a prepregging method. Then, the CFRP’s mechanical and electrical properties were evaluated. The results show that the compressive, interlaminar shear strengths and Mode I interlaminar fracture toughness were improved from the control by 22％, 11％ and 48％ respectively with only 0.39 wt ％ CNTs. The electrical conductivities in both the 90° and through thickness directions were improved by two to three orders of magnitude. The SEM and TEM observations of the composites revealed that the CNT/epoxy resin layer of 100-200 nm thickness was formed at the fibermatrix interphase. These results indicate the importance of designing the fiber-matrix interphase to improve the mechanical and electrical properties of fiber reinforced polymer composites.