Carbon nanotube reinforced composites: Potential and current challenges

The remarkable mechanical properties exhibited by carbon nanotubes have stimulated much interest in their use to reinforce 14 advanced composites. Their elastic modulus is over I TPa and tensile strength is over 150 GPa, which makes them many times stiffer and stronger than steel while being three to five times lighter. In promoting their products, several manufacturers of sports equipment have advertised carbon nanotubes as reinforcements of some of their top of the line products. This paper evaluates the technical and economic feasibility of using carbon nanotubes in reinforcing polymer composites. It is concluded that carbon nanotubes can be used in conjunction with carbon fibers in a hybrid composite in order to achieve elastic modulus values in the range 170-450 GPa. As the sole reinforcing phase, carbon nanotubes present a viable option if elastic modulus values on the order of 600 GPa are desired. These conclusions are confirmed by a case study to select the optimum material for a tennis racket using the analytic hierarchy process. The discussion also shows that carbon nanotubes face several challenges, which need to be overcome before they can be widely used. They need to be produced in larger quantities at a lower cost, they need to be synthesized in longer lengths, and improved techniques are required to align and evenly distribute them in the matrix. (c) 2006 Elsevier Ltd. All rights reserved.