Enhancement of the mechanical properties of carbon nanotube/phenolic composites using a carbon nanotube network as the reinforcement

Both theoretical analyses and experimental studies have demonstrated that carbon nanotubes (CNTs) have extremely high strength and modulus. The outstanding intrinsic mechanical properties have attracted researchers to adopt CNTs as a reinforcement for composites. On the other hand, several primary draw-backs of adopting CNTs as the reinforcement were re-ported. These involved non-uniform dispersion of CNTs in matrix, less effective load transfer from matrix to CNTs, weak interactions between shells in CNT, and alignment control of CNTs in matrix. Melt mixing is generally adopted to introduce CNTs into resin. However, the agglomeration of CNTs in matrix generates defects in composites and thus reduces the mechanical properties of the composites. In this study, dispersed CNTs and network CNTs synthesized from the thermal chemical vapor deposition method (CVD) were adopted as the reinforcement. In the case of adopting dispersed CNTs as the reinforcement, CNTs were obtained from the milling process of the as-grown CNTs. The composites reinforced by the dispersed CNTs were fabricated through the melt mixing method. On the other hand, the network CNT composites were fabricated through the resin infiltration method by introducing the resin into the CNT network. Comparisons in mechanical properties between the network CNT composites and the dispersed CNT composites are the focus of this work. Moreover, fracture morphologies were also examined and discussed.