Interfacial mechanical properties of carbon nanotube-deposited carbon fiber epoxy matrix hierarchical composites

Functionalized multiwalled carbon nanotubes were successfully deposited on carbon fibers using four different techniques including dip coating, hand layup, spray up and electrophoretic deposition (EPD). A uniform coating of nanotubes was achieved from EPD in comparison to other coating techniques. Later nanotube-coated fibers by EPD were introduced in epoxy resin to investigate interfacial mechanical properties of the developed hierarchical composites by vacuum bagging technique. The increases in flexural and interlaminar shear properties up to 15% and 18% were observed in composites containing nanotube-coated carbon fibers than composites with virgin carbon fibers, respectively. Microscopic observation revealed the proper impregnation of multiscale reinforcements, i.e., carbon fibers and carbon nanotubes, in resin along with the modification of fiber/matrix interface due to the presence of nanotubes at interface. Finally, the mechanisms for improved mechanical properties were identified along with the presentation of a schematic model for better understanding of the improved performance of hierarchical composite after depositing uniformly dispersed nanotubes on carbon fibers.