Effect of CNT functionalization on crack resistance of a carbon/epoxy composite at a cryogenic temperature

In this study, the authors attempted to enhance the crack resistance of a carbon/epoxy composite by adding carbon nanotubes (CNTs) into the resin formulation. Prior to applying CNTs, a chemical surface treatment, amino-functionalization, was conducted to enhance the interfacial bonding between CNTs and epoxy resin. The resultant increase in tensile strength was attributed to good interfacial bonding quality. Two kinds of 3-phase carbon/CNT-epoxy unidirectional prepregs were fabricated via a hot-melting process with the addition of CNTs. The CNT-reinforcing and -functionalizing effects were investigated through DCB tests and measurement of the acoustic emission (AE) signal of a cross-ply specimen both at RT and at −150 °C. The carbon/epoxy composite containing functionalized-CNTs showed improved interlaminar fracture toughness and transverse crack resistance at the cryogenic temperature.