Abstract
Abstract
Smart structures are gaining importance especially in the field of lightweight design. Use of actuators, sensors and electronics buried in the load bearing structure offers the opportunity for noise reduction, vibration and shape control, micro positioning and health monitoring. First active solutions are based on commercially available bulk and multilayer actuators. They show high stiffness, high blocking forces and short response times but they are very fragile with low damage tolerance against non-axial loads. Mounting of these monolithic actuators into structural components needs therefore additional mechanical interfaces. Furthermore, geometry of multilayer actuators is limited to rectangular shapes and a set of defined sizes. To overcome these drawbacks, solutions based on piezocomposites have been investigated during the last decade. At present, mainly low profile piezocomposite actuator types have been commercialized, as for example the ACX-module [1], the Active Fiber Composite (AFC) [2] and the Macro Fiber Composite (MFC) [3]. These sheet piezocomposites consist mainly of a monolayer of PZT fibers or rods longitudinal arranged between two polymer sheets and electrodes. They are available as 3-3 (d33- effect) or 3-1 (d31-effect) modules. These piezocomposites are suitable for application on flat surfaces but not for voluminous structures. Voluminous 1-3 Piezocomposites based on PZT rods or fibers are well established as ultrasonic transducers. The Fraunhofer IKTS recently developed custom shape piezocomposites based on PZT tubes and plates which represent a new generation of piezoceramic devices. Acting in the d31-mode (contraction), the new actuators are especially characterized by tolerating to some extend non-axial and torsion loads. They can be easily formed according to custom design which makes them suitable for integration in various structural components. Because electric field is only dependent on wall thickness of the PZT tubes or plates low voltages are necessary to drive the piezocomposites as actuators [4]. This present paper gives an overview of available piezocomposite devices and an update of new components designed for actuator, sensor, health monitoring and energy harvesting applications.