Researches of smart materials in Japan

The choice of sensor and actuator material as well as optimum design to combine the actuator element with the host structure become very essential to develop a smart materials and structures. In the present paper, first, the present state and issues of the main solid actuators are described from the viewpoint of material science and engineering. Next, the developments of smart materials and systems using shape memory materials in Japan are introduced. Shape memory TiNi fiber reinforced/Al or polymer matrix composites have been fabricated to confirm the enhancements of fracture toughness (K-value) by utilizing the compression stresses caused by shape memory shrinkage of embedded TiNi fibers. Sudden failure prevention system four structures are also proposed by combining non-destructive acoustic emission detecting system with suppression of crack-tip stress intensity by shape memory shrinkage effect. Lastly, the research project scheme and several targets on smart actuator development are introduced, which are imposed on the Tohoku University team in the Japanese National Project (1998-2002 A.D.) on Smart Materials and Structure System by NEDO/MITI.