INTEGRATION OF SENSORS AND ACTUATORS TO SUPPRESS VIBRATIONS ON CARBON FIBER STRUCTURES

Composite materials, such as carbon fiber, offer several advantages with respect to traditional alloys, i.e. reduced mass, high stiffness and low thermal expansion. However, when realizing mechanical structures using these materials, some problems must be considered. In particular their small damping can cause high dynamic amplification of vibrations, especially when the structure is forced near its natural frequencies. These vibration phenomena can be very dangerous, causing unwanted system behaviour and structural failures. Active control techniques have been widely developed to suppress vibration and great progresses have been achieved. In this field researches on sensors and actuators and on their integration into the structure have a great importance. In the last years a class of materials, called smart, has been widely developed. These transducing materials, which are able to convert mechanical energy into another form (electrical, magnetic, thermal, etc) and vice versa, are suitable for the realization of both sensors and actuators. The paper discusses the opportunity to use piezoelectric actuators (PZT) and Fiber Bragg Grating sensors (FBGs) to realize a smart structure embedding both the sensing and the actuating devices. Fiber optic strain sensors, have a great potential in the use in smart structures thanks to their small transversal size and the possibility to make an array of many sensors. They can be embedded in carbon fiber structures and their effect on the structure is nearly negligible. Such a structure is able to measure its state of excitation and to reduce the amplitude of vibration using the embedded actuators. Control forces are designed to increase the damping of the structures, thus suppressing undesired vibration. Different control strategies can be synthesized to achieve the best performance exploiting potential of distributed sensors and actuators.