Structural Damping Using a Four Layer Sandwich

Abstract

A serious limitation in the use of sandwich type damping with a single viscoelastic material is that the effectiveness is very frequency dependent. Practical applications demand a high overall loss factor over a wide frequency range. It is shown that this requirement can be met with a dual core made from two viscoelastic layers with very different values for the shear modulus, one to be at least 100 times greater than the other. This makes the construction asymmetric and the equations of motion have been derived using Hamilton’s energy principle. The solution cannot be given in closed form but computer results have been verified by experiment. Comparison with unconstrained layer damping and with 3-layer construction with an equal thickness damping layer has demonstrated the much wider frequency effectiveness of the 4-layer sandwich.