Active fiber composite actuators for reducing acoustic radiation from cylindrical shells

Abstract

Active fiber composites were developed to provide a mechanically robust method for large-area, orthotropic actuation and sensing in active structures. This presentation will describe the application of active fiber composite actuators to the reduction of acoustic radiation from a cylindrical shell by active control. The composite actuation layer is formed by small diameter piezoelectric fibers that are unidirectionally aligned and imbedded in a resin matrix system. A separate, etched, interdigital electrode layer makes the electrical connections. By nature of its structure, an active fiber composite actuator or sensor allows use of the primary piezoelectric effect in the plane of the composite. Active fiber composites are inherently tolerant of damage and can be conformed to a wide range of structural shapes. To control acoustic radiation from a cylindrical shell, active fiber composite actuators are used to generate a strain field that counteracts the strain associated with acoustically efficient shell motions. Optimal placement of the actuators is determined using numerical models verified by an experimental characterization of the shell dynamics. The control signal applied to the actuator is determined, in real time, using adaptive control. Error sensing methods using accelerometers or active fiber composite sensors were considered. [Work supported by DARPA.]