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Structural fin or wing vibrations are observed on high performance aircraft when flying at high angles of attack. The severity of the so-called buffeting vibration depends on the aircraft configuration and aerodynamic optimization of the configuration. The vibrations are caused by flow fluctuations resulting from flow separation at wings or from bursting of wing leading edge and front fuselage vortices. The resulting dynamic loads together with manoeuvre loads lead to increased material fatigue and may require an augmented effort in aircraft maintenance.A number of different concepts have been proposed to either minimize the buffeting excitation by passive devices or to alleviate the resulting structural vibrations by active control systems. One of the most innovative suggestions has been to use piezoelectric patch actuators distributed across the surface of a vertical tail to actively induce a counter-strain into the structure. This concept promises to efficiently suppress vibrations of elastic modes with low aerodynamic damping up to high frequencies without an excessive amount of additional weight.In order to investigate the performance of such a system a collaborative research project was initiated between DaimlerChrysler Aerospace -Military Aircraft Division and DaimlerChrysler Research and Technology within the framework of the Advanced Aircraft Structures program. For this purpose a demonstrator was conceived, designed and manufactured that is dynamically equivalent to a typical fighter aircraft vertical tail and simulates its structural set-up. Custom-made actuator modules were surface-mounted onto the fin-box demonstrator in locations prescribed by a design optimization scheme to provide optimal actuation authority up to 200 Hz. A series of tests have been performed to determine the structural dynamic behaviour of the test-box and to validate the mathematical model and calculation methods. Both open and closed ioop tests show excellent agreement with the theoretical expectations and indicate the potential for significant vibration reduction for on-ground conditions and consequently might lead to buffet alleviation in flight using this technology.The effectiveness of buffeting alleviation at relevant flight conditions has to be demonstrated via total aircraft dynamic buffet response calculations and needs verification by flight test.

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Up to now experimental and theoretical research on active structures for aerospace applications has put the focus mainly on surface bonded actuators. Simultaneously piezoceraniics became the major type of actuating device being investigated for smart structures. In this context various techniques of insulating, bonding and operating these actuators have been developed. However, especially with regard to actuators only a few investigations have dealt with embedding of these components into the load bearing structure'9 so far. With increasing shares of fibre-reinforced plastics applied in aerospace products the option of integrating the actuation capability into the components should be reconsidered during the design process.This paper deals with different aspects related to the integration of piezoceramic actuators into fibre reinforced aerospace structures. An outline of the basic possibilities of either bonding an actuator to the structure's surface or embedding it into the composite is given while the emphasis is put on different aspects related to the latter technology. Subsequently recent efforts at Daimler-Benz Aerospace Domier concerning aircraft components with surface bonded actuators are presented.Design considerations regarding embedded piezoceramic actuators are discussed. Finally some techniques of nondestructive testing applicable to structures with surface bonded as well as embedded piezoelectric actuators are described.