J. Phys. Chem. C 2007, 111, 17865-17871
17865
Functionalized Single-Walled Carbon Nanotubes for Carbon Fiber-Epoxy Composites† Elena Bekyarova,‡ Erik T. Thostenson,§ Aiping Yu,| Mikhail E. Itkis,| Danylo Fakhrutdinov,‡ Tsu-Wei Chou,§ and Robert C. Haddon*,| Carbon Solutions Inc., RiVerside, California 92507, Department of Mechanical Engineering and Center for Composite Materials, UniVersity of Delaware, Newark, Delaware 19716, and Center for Nanoscale Science and Engineering, Departments of Chemistry and Chemical and EnVironmental Engineering, UniVersity of California, RiVerside, California 92521 ReceiVed: February 16, 2007; In Final Form: May 3, 2007
Functionalized single-walled carbon nanotubes (SWNTs) are explored as nanoreinforcement for carbon fiber/ epoxy composites. SWNTs functionalized with carboxylic acid groups (SWNT-COOH) are dispersed in epoxy and are used for infiltration of carbon fabric (CF) by the vacuum-assisted resin transfer molding technique to fabricate SWNT-COOH/epoxy/CF composites. Mechanical tests demonstrate that the incorporation of SWNT-COOH improves the mechanical performance of the composites and produces a 40% enhancement of the shear strength at a SWNT-COOH loading of 0.5 wt %.
1. Introduction Single-walled carbon nanotubes (SWNTs) are considered to be the ideal reinforcing agent for advanced polymer composites because of their tremendous mechanical strength, exceptional electronic and thermal properties, nanometer scale diameter, high aspect ratio, and light weight.1-4 This has prompted intensive studies on composites based on this material.5-15 It was soon realized that the main obstacle in the translation of the outstanding physical properties of carbon nanotubes into useful multifunctional composite materials is the nonreactive nature of the carbon nanotubes, which ultimately leads to a weak interfacial interaction with the polymer matrix that results in inefficient load transfer and phase separation. Thus, molecular level design of the nanotube-polymer interface is essential for the fabrication of high-performance nanocomposites. Various approaches have been employed for the optimization of the polymer-SWNT interface so as to ensure efficient stress transfer from the polymer matrix to the nanotube lattice.1,6,7,15-25 The ultimate interface is realized by constructing chemical bonds, the strongest type of interfacial interaction, between the nanotubes and polymer matrix.10,13,22,24-26 In addition, the formation of a polymer-SWNT covalent bond can produce homogeneously blended SWNTs in which phase separation is precluded by chemistry. Molecular simulations suggest that the introduction of a relatively low density (
