<title>Performance characteristics of active constrained layer damping versus passive constrained layer damping with active control</title>

Abstract

The shear strains in the visco-elastic cores of beams controlled by Active Constrained Layer Damping (ACLD) treatments are determined and compared with those of beams controlled by Active Control (AC) and conventional Passive Constrained Layer Damping (PCLD) treatments. Such comparison is essential in quantifying the individual contribution of the active and passive damping components, to the overall damping characteristics, when each operates separately and when both are combined to interact in unison as in the ACLD treatments. The comparisons are based on distributed-parameter and finite element models which describe the behavior of beams controlled by ACLD as well as beams treated by AC and PCLD treatments. The distributed-parameter models give closed-form expressions for the energy dissipation characteristics of the ACLD treatments in comparison with those of the AC/PCLD treatments. Also, the finite element models are validated experimentally using visco-elastic cores which are photo-elastic in order to study the distribution of the shear strains inside these cores. The results obtained indicate that the ACLD treatments are capable of developing shear deformations, in the visco-elastic cores, higher than those generated by the AC/PCLD treatments when the ratio of the longitudinal rigidity of the constraining layer to that of the base beam is less than 1. With such enhanced shear deformation capabilities, the ACLD treatments can develop high damping and effective attenuation of the vibration of critical systems as the blades of rotorcrafts.