Reducing Vibration in Carbon Fiber Structures with Piezoelectric Actuators and Fiber Bragg Grating Sensors

Carbon fiber structures are claimed to offer several advantages such as contained mass, high stiffness and low thermal expansion. However, these structures are characterized by a very low mechanical damping and, therefore, they are easily subjected to potentially dangerous vibratory phenomenon. Active control techniques have been widely developed to suppress vibration and great progresses have been achieved. On the other hand the research on sensors and actuators to be used is still a field of interest. The paper discusses the opportunity to use piezoelectric actuators (PZT) and Fiber Bragg Grating sensors (FBG) to realize a smart structure including in itself both the sensing and the actuating devices. Fiber optic strain sensors, such as Fiber Bragg Gratings, 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. Even if this is not the case of the reported study, they can be embedded between carbon fiber layers and their effect on the structure is usually negligible. Such a structure is able to measure its state of excitation and to reduce the amplitude of vibration using the PZT actuators. Different control strategies have been implemented on a test rig consisting on a carbon fiber cantilever beam with 14 FBG sensors and 3 PZT actuators. Control forces are designed to increase the damping of the structures, allowing to increase of damping of the first modes of vibration of about 10 times.