Mechanical properties of functionalized nanotube buckypaper composites

Buckypapers of long SWNTs and MWNTs were functionalized using m-Chloroperoxylbenzonic acid (m-CPBA). After functionalization, epoxide groups were introduced on the sidewalls, which can react with the curing agent of epoxy resin to cross-link with the epoxy resin matrix and form covalent bonding to improve interfacial bonding and load transfer between the nanotubes and the matrix. The tensile test results show that the tensile strength and modulus of the functionalized MWNT BP composites noticeably improved. The tensile modulus of the functionalized SWNT BP composites increased, but its tensile strength was decreased due to possible large property degradation of the functionalized SWNTs. The improvement of interfacial bonding and loading transfer are evidenced by mechanical property improvements, nanotube breaks, good interfacial bonding at the fracture surfaces, and failure mode changes of the resultant composites. The functionalized MWNT BP composites show high mechanical performance, comparable to carbon fiber fabric composites for structural applications. The developed functionalization method and composite fabrication technique have the potential to scale up for industrial applications.