Interlaminar Fracture Toughness of WovenCarbon Fabric Composites Reinforced withMWCNTs

Double cantilever beam (DCB) tests have been carried out on woven carbon fabric composite specimens produced using carboxyl functionalized multi-walled carbon nanotubes (COOH-MWCNTs)/epoxy nanocomposites to determine their mode I interlaminar fracture toughness of the specimens. In addition to the neat epoxy woven fabric composite specimens, three loadings of COOH-MWCNTs were examined in this study: 0.5%, 1.0%, and 1.5%. The loading and the resistance curves (R-curves) for all specimens were compared. The results showed a 52%, 91% and 160% increase in maximum critical energy release rates with the addition of 0.5%, 1.0% and 1.5% MWCNTs respectively. It is suggested that additional energy consumption mechanism due to the bridging effect of the COOH-MWCNTs at the interface increased the interlaminar fracture toughness. Furthermore, the significant deformations observed at the interface suggests that linear elastic fracture mechanics (LEFM) method of analysis should be replaced by elastic plastic fracture mechanics (EPFM) or quasi brittle fracture mechanics (QBFM) to accurately determine the fracture toughness of FRP composites reinforced by carbon nanotubes (CNTs).