Interface finite elements for the modelling of constrained viscoelastic layers

Viscoelastic treatment has traditionally been used in industrial applications to reduce structural noise and vibration by dissipating part of the strain energy. Constrained-layer damping (CLD) treatments usually dissipate more energy than free-layer damping treatment (FLD), but its design must be integrated in the design process of the structure to be damped. Parametric studies are then necessary to determine the optimal viscoelastic material forming the CLD treatment, and the optimal placement and thickness of the layer. For structures with complex geometry, 3D finite elements are required and a change in the thickness or the placement of the viscoelastic layer implies a complete remeshing of the structure, which represents a significant additional computational cost in the parametric study. The goal of this work is to present a new strategy to model efficiently thin constrained viscoelastic layers. Two interface finite elements, based on a surface representation of the damping layer, are proposed. The first one is a joint element using relative displacements at the interface, and the second one is an original zero-thickness element which makes use of a volumetric integration. These elements are validated by comparison with 3D finite elements. Results show that the proposed interface elements allow a good representation of the damping layer's behaviour, especially for thin layers. Moreover, this modelling approach can be efficiently used in the context of parametric optimisation.