Effect of Grafted CNT on Carbon Fibers on Impregnation Properties of Carbon Fiber Reinforced Polyamide 6

Abstract

Since thermoplastic resins have a higher viscosity than thermosetting resin during the molding process, it is necessary to develop a method for impregnating resin into the carbon fiber bundle at the molding of carbon fiber reinforced thermoplastic (CFRTP). Recently, a method for grafting carbon nanotubes (CNTs) on the surface of carbon fibers has been developed. It has been reported that CNT grafted carbon fibers have higher fiber/matrix interfacial shear strength, and one of the reasons for this result is considered to be the improvement of wettability. Therefore, it can be expected that grafting CNT on carbon fiber surfaces can be used not only for obtaining high fiber/matrix interfacial shear strength, but also as a technique for ensuring the impregnation property of the matrix resin. In this study, grafting CNT on the carbon fiber surface was focused on as a method for improving the impregnation property. The fiber/matrix interfacial shear strength, wettability of a single fiber and fabric surface, and impregnation property of CF/PA6 laminates were evaluated. By grafting CNTs on the surface of carbon fibers, the single fiber had higher wettability and higher fiber/matrix interfacial shear strength than untreated carbon fiber. CNT grafted plain woven carbon fiber fabrics with CNT deposition times of 30 and 60 minutes had higher wettability with PA6 resin than untreated plain woven fabrics. In the case of CNT deposition time of 30 minutes, CF/PA6 laminates with excellent impregnation were obtained, while CF/PA6 laminates made with CNT deposition time of 60 minutes had partly higher void content since excessive CNTs restricted the inflow of resin into carbon fiber bundles.