This paper is to propose an innovative damping design termed intelligent constrained layer (ICL). This technique integrates active and passive dampings through constrained layer treatments to enhance system reliability and to provide adjustable damping. The proposed ICL damping design consists of a viscoelastic shear layer sandwiched between a piezoelectric constraining cover sheet and the structure to be dampened. According to measured vibration response of the structure, a feedback controller regulates axial deformation of the piezoelectric layer to perform active vibration control. In the meantime, the viscoelastic shear layer provides additional passive damping. The active damping component of this design will produce adjustable and significant damping. The passive damping component of this design will increase gain and phase margins, eliminate spillover, reduce power consumption, improve robustness and reliability of the system, and reduce vibration response at high frequency ranges where active damping is difficult to implement. To model the dynamics of ICL, an eighth-order differential equation governing bending vibration of an elastic beam with the ICL treatment is first derived. Then an ICL treatment using an idealized, distributed sensor and a proportional-plus-derivative feedback controller is illustrated on a semi-infinite elastic beam subjected to standing wave excitations. Numerical results show that ICL will produce significant damping. The allowable deflection slope of the beam in order not to saturate the piezoelectric layer is also calculated.

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