Distribution of active and passive constraining sections for hybrid constrained layer damping treatments

This paper investigates the effect of the distribution of the active and passive constraining materials on the damping performance of an active-passive hybrid constrained layer (HCL) treatment. Earlier studies have demonstrated that the HCL can provide higher open-loop and closed-loop damping than an active constrained layer (ACL) system when a stiffer passive material is integrated into the cover sheet and the coverage ratio of the active-to-passive materials is appropriately designed. The objective of this research is to advance the state of the art in HCL system studies by investigating the effect of multiple active and passive constraining section distributions and the effect of host structure strain fields (mode shapes) on the treatment performance. Using a simple supported beam as an example, these effects are examined and quantified. The findings provide deeper insight toward HCL operations and will be useful in forming guidelines for HCL designs.