The role of multi‐walled carbon nanotubes in epoxy nanocomposites and resin transfer molded glass fiber hybrid composites: Dispersion, local distribution, thermal, and fracture/mechanical properties

Hybrid composites containing endless glass fiber reinforcement and surface‐functionalized carbon nanotubes (CNTs) dispersed in the matrix phase were produced by resin transfer molding (RTM). An efficient surface modification of the nanotubes enhances the compatibility with the matrix system and the dispersion quality, enabling the impregnation process via liquid composite molding. We assessed the quality of the RTM process by newly developed methodologies for the quantification of the filtering of CNTs. First, we established a method to analyze the CNT length distribution before and after injection for thermosetting composites to characterize length‐dependent withholding respectively the size distribution of nanotubes in the hybrid composites. Second, the resulting test laminates were locally examined by Raman spectroscopy and compared to reference (nanocomposite) samples of known CNT content to non‐destructively quantify the local CNT concentration along the resin flow path. Moreover, the thermal and mechanical properties of the modified composites were investigated. The nanocomposites containing 0.5 wt% surface‐functionalized CNTs exhibited superior ductility and increased fracture toughness. Glass fiber hybrid composites containing 0.5 wt% functionalized CNTs in the resin phase exhibited increased fracture toughness in mode I and a slight deterioration in mode II due to the constrained formation of hackles. POLYM. COMPOS., 38:1849–1863, 2017. © 2015 Society of Plastics Engineers