Electrostatically tunable bending stiffness in a GFRP-CFRP composite beam

The suppression of vibrations in structures is commonly considered a useful measure for the extension of their lifetime, when high amplitude vibrations are observed. In the experiments presented in this work, the modification of the stiffness of a beam as a means to suppress vibrations due to resonance is proposed as an alternative to the introduction of discrete damping devices. The stiffness of a beam is modified by applying an electric field between the main element of the structure and additional stiffening elements applied to its surface, thus coupling the latter to the former by transfer of shear stresses. The effect of electrostatic tuning of the bending stiffness (and consequently of its eigenfrequencies) of a large size GFRP-CFRP beam is shown by the shift of the resonance peak for the first bending mode to higher frequencies. The discrete character of the stiffness increase in multi-layer beams (n >= 3) is postulated.