Hybrid vibration control of laminated composite structures using magnetostrictive and hard damping materials

Smart laminated composites with layers of magnetostrictive and/or piezoelectric materials have been explored for active damping applications. Active vibration control in laminated structures with low inherent damping, may lead to instability. In some other cases ae flexible appendages of satellites, design considerations may impose constraints in collocated sensing and actuation in structure which would also cause degradation in system performance if only active control is used. Ideally, both structural damping and active control are desirable to achieve good dynamic performance. Of late, hard ceramic materials with hysteretic stress-strain behavior are used in passive vibration control. Because of high strain dependency of the damping in these materials, especially near the high damping regime, it is possible to enhance the amount of passive damping by active control of strain in the passive layer. Because of the layered structure in laminates, several interesting possibilities for hybrid damping exist and a few of them are proposed and explored in the present study. Smart composites with magnetostrictive (Terfenol-D) layers and strain dependent ceramic and/or ferroelectric Passive Damping(PD) layers are considered. The damping achieved in the PD layers is controlled by varying their location and/or the amount of gain in the active controller. Both frequency and time domain studies are carried out to investigate the performance of proposed hybrid damping systems. Simulations using recently developed smart beam elements are carried out on laminates with several configurations of active and passive layers. The simulation brings out the significance and the exploitation of strain dependency of passive damping on the overall damping of the hybrid system.