Experimental results for stand-off passive vibration damping treatment

A quantum leap in the performance of vibration damping for structural panels has been provided by the development of a practical spacer (or stand off) layer. The thicker the stand off layer, the greater the performance and the efficiency of the damping treatment. The thickness of the stand off layer behaves much as the depth of an I-beam with regard to structural efficiency. Selected experimental results as well as some theory and practicalities of spaced or stand off damping for structural panels are presented and discussed. The basic theory of spaced or stand off damping has been well known since the late 1950s. The two essential features of a spacer or stand off layer are that the shear stiffness must be relatively high and that the flexural stiffness must be relatively low. For a homogeneous layer, these are mutually exclusive requirements. Practical stand off damping treatment systems originally developed in the late 1980s are described. A variety of applications in the laboratory, in flight, and in service have been developed and selected data are presented. Passive stand off vibration damping treatment systems have achieved a large degree of success and maturity, even though there are many significant opportunities for further technological advancements. There have been high payoff applications where passive damping has played a vital role in suppressing vibration and noise.