The concept of enhancing energy dissipation in thin beams and panels by adding viscoelastic materials to a structure dates back at least to the early 1950s. Kerwin in 1959 was the first to present a general analysis of viscoelastic material constrained by another metal layer. He made several key simplifying assumptions in the mathematics, as did DiTaranto (1965) and Mead and Markus (1969) in follow-up studies: (1) the constraining layer bends in the transverse direction exactly as the base layer, (2) the viscoelastic layer undergoes pure shear, and (3) the viscoelastic layer does not change its thickness during deformation. While appropriate for damping problems of that time, the role of passive, and now active, damping has expanded in the decades since to the point that many problems of practical engineering interest are no longer represented well by these mathematical models. This paper explores a few pitfalls of simplified modeling through some trade studies using benign-looking sandwich beams. The Mead and Markus assumptions are implemented using finite elements and are compared to a beam comprised entirely of higher order elements. A sandwich beam is also modeled using Euler-Bernoulli beams (acting independently) as facesheets and a linear element for the viscoelastic material, similar to how a sandwich might be modeled using standard elements in a commercial code. The accuracy of damping predictions is inferred from the accuracy of strain energy distributions.
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