SMART STRUCTURES DESIGN WITH CARBON NANOTUBES

摘要

Graphite and diamond are the well-known forms of carbon. In the middle of the 80's a third variation of appearance of carbon was discovered. These structures have a strong resemblance to the domed buildings of the American architect Richard Buckminster Fuller and that is the reason why they are called fullerenes. In 1991 Sumio Iijima in Japan noticed another tubular carbon structure which consists of closed cylindrically shaped graphite planes. These so called Carbon-Nanotubes (CNT) are 1-50 nm in diameter and can reach the length of a few micrometers. CNT rank among the materials with the highest stiffness and strength ever built and indicate an enormous potential to develop new types of fibre reinforced composites. Beside their distinguished specific structural properties CNT show excellent properties for use as an actuator as well. The combination of these properties in one material offers completely new capabilities to develop adaptive structures. Currently various applications of this new material are under discussion and are investigated fundamentally (e.g. hydrogen storage, molecular filters and membranes, nano-conductor paths, electric switches, field emitter, flat screens ...). First publications of experimental investigations proof that CNT have a 29 times higher specific working capacity than ferroelectric material (e.g. piezoceramic). For use as an actuator it is necessary to operate the CNT in an electrolyte. The activation occurs by applying an electric field. The capability of transforming electric energy into mechanical energy in combination with extreme high strength (～30 GPa) and stiffness (～1 TPa) makes CNT an ideal material for future adaptronic systems.