Simultaneous Extension and Shear Piezoelectric Actuation for Active Vibration Control of Sandwich Beams

Piezoelectric materials are widely used as distributed means for sensing and/or actuating a structure's response, either by bonding them to the surfaces of a structure or embedding them into a laminate structure. Surface-mounted actuators are normally poled in thickness direction so that they work in the extension mode, while embedded actuators are more effective when poled in the longitudinal direction and thus working in the thickness-shear mode. It has been shown that embedded shear actuators may lead to less problems of actuators damage and debonding, minor dependence on actuators position, and length and smaller stresses in the actuators. It has also been observed that the surface-mounted extension actuators are generally more effective for very flexible host structures while embedded shear actuators are more effective for stiffer structures. These and other distinctive features of extension and shear actuators may be exploited to study their simultaneous use and to design a combined extension—shear actuated beam. Hence, this work presents the results of a numerical investigation of active vibration control using simultaneous extension and shear piezoelectric actuation for a clamped—clamped sandwich beam. The analysis is carried out using a laminate/ sandwich beam finite element model combined to an optimal control with limited input. Results show that simultaneous use of extension and shear actuators is very promising since their actuation mechanisms are complementary. In particular, a good damping performance was obtained over an increased frequency-range with very localized actuators.