Experimental identification of smart material coupling effects in composite structures

Smart composite structures have an enormous potential for industrial applications, in terms of mass reduction, high material resistance and flexibility. The correct characterization of these complex structures is essential for active vibration control or structural health monitoring applications. The identification process generally calls for the determination of a generalized electromechanical coupling coefficient. As this process can in practice be difficult to implement, an original approach, presented in this paper, has been developed for the identification of the coupling effects of a smart material used in a composite curved beam. The accuracy of the proposed identification technique is tested by applying active modal control to the beam, using a reduced model based on this identification. The studied structure was as close to reality as possible, and made use of integrated transducers, low cost sensors, clamped boundary conditions, and substantial, complex excitation sources. PVDF (PolyVinyliDene Fluoride) and MFC (MacroFiber Composite) transducers were integrated into the composite structure, to ensure their protection from environmental damage. The experimental identification described here was based on a curve fitting approach combined with the reduced model. It allowed a reliable, powerful modal control system to be built, controlling two modes of the structure. A Linear Quadratic Gaussian algorithm was used to determine the modal controller-observer gains. The selected modes were found to have an attenuation as strong as -13dB in experiments revealing the effectiveness of this method. In the present study a generalized approach is proposed, which can be extended to most complex or composite industrial structures when they are subjected to vibrations.