Dispersion and Related Properties of Acid-Treated Carbon Nanotube/Epoxy Composites using Electro-Micromechanical, Surface Wetting and Single Carbon Fiber Sensor Tests

Studies of dispersion and related properties, in carbon nanotube/epoxy composites, were conducted using electro-micromechanical and wettability tests. Specimens were prepared from neat epoxy as well as composites with untreated and acid-treated carbon nanotube (CNT). The degree of dispersion and its standard deviation were evaluated by turbidity of the dispersing solution, as well as by volumetric electrical resistivity. Acetone was a better dispersing solvent than purified water and various acid treatments of the CNT also enhanced dispersion. Contact resistivity responded differently with dispersion degree. The apparent Young's modulus was higher for composites with acid treated CNT. The interfacial shear strength between a single carbon fiber and CNT/epoxy was lower than that between a single carbon fiber and neat epoxy. This difference is attributed to increased viscosity and decreased bonding availability in the matrix due to the added CNT. The optimum CNT treatment, for maximizing interfacial adhesion while maintaining good electrical conductivity was the sulfuric acid treatment. The CNT composites can also sense micro-damage in terms of the stepwise increments of electrical resistivity combined with acoustic emission.