Some design considerations for active and passive constrained layer damping treatments

Active constrained layer damping treatments promise to be an effective means of vibration suppression in structures. Basically, the concept consists in either replacing or augmenting the constraining layer of a constrained viscoelastic material with piezoceramic actuators in an attempt to improve vibration suppression properties by capitalizing on both passive and active damping techniques. An important issue in such configurations is the concept that the actuation ability of the piezoceramic is reduced by the viscoelastic layer, rather than enhanced. On the other hand, an active constraining layer increases the shear in the viscoelastic and thus forms an effective means of enhancing the damping mechanism. Some design considerations for pure passive, pure active control, and active constrained layer damping are discussed here. Several authors have reported comparisons and formulations of active constrained layer damping techniques. The approach presented here differs in that it employs an energy principle for the equations of a beam with partial active/passive constrained layer damping treatments. To simulate a realistic design problem, the optimal sizing, length, and thickness of treatments subject to a total thickness restriction is studied for cases of active constrained layer, passive constrained layer, and pure active control. The results show that the active constrained layer damping treatment provides better vibration suppression than passive damping treatments, and it even out-performs pure active control for low-gain applications.