Lightweight damping of composite sandwich beams: Experimental analysis

The purpose of this article is to experimentally study the damping of composite sandwich beams with lightweight honeycomb core. The top and bottom facesheets are made of carbon/epoxy layers with partial interleaved viscoelastic layers. A new damping approach consisting of selectively targeting the inflection points of the bending mode shapes is proposed. At the nodes, the shearing deformation in the beam is maximal, and so is the strain in the viscoelastic layers. The experimental investigation of damping is made by means of standard impact tests using an instrumented hammer performed on beam specimens. The nodes are determined experimentally by moving a small accelerometer along the beam axis and by measuring the amplitude of the acceleration at each point. This novel damping approach keeps the damping ratio as high as the ratio obtained with standard (full coverage) surface damping treatment while reducing the added mass by almost 50%. A comparison of the results obtained in this study with experimental and numerical results found in the literature leads to the conclusion that the most efficient way of damping this type of sandwich structure is to modify and/or improve the viscoelastic properties of the core.