Adaptive Vibration Damping of Fin-Structures.

Abstract

One major problem of modem military aircraft is the buffet loading on the fin structures. Flying the aircraft at high angles of attack allows vortices, evolving from the leading edge of the wing, to hit the fin and excite struc-tural vibrations. This leads to increased fatigue loads as well as reduced aircraft manoeuvrability and flight enve-lope. In this paper an adaptive structural system is presented, that has been developed with the aim of reducing these fin vibrations. The adaptive system uses an ACTIVE INTERFACE to dynamically introduce counteracting forces that cancel out the aerodynamically induced vibrational loads. This interface concept is based upon the integration of piezoelectric elements directly into the bending support of the fin structure. Therefore, the piezoelectric materials were extensively tested in order to characterise their performance under the expected very high load levels. sub-sequently, a FE-model of the fin structure was investigated, mode shapes and eigenfrequencies were extracted. The active interface was designed and manufactured and it was finally integrated into a full scale testing structure. Tested under realistic loading conditions, it proved to have the necessary authority over the aerodynamic vibration loads. The results of these investigations will be given in this presentation.