Enhancement and evaluation of damping performance in layered CLD type coatings

One of the highly effective Layered damping methods is Constraining Layer Damping (CLD), wehrein a layer of viscoelastic (VE) material is sandwiched between the host structure and a stiff Constraining Layer (CL). Traditional CLD uses metallic Cls and hence all the damping comes from the VE layer. However, Cls of certain nonmetallic and/or anisotropic materials with significant inherent damping can be considered to enhance the net damping performance. A single degree of freedom (SDOF) model is presented here to investigate the performance of layered damping coatings comprising a VE layer and a stiff CL. The proposed model considers both the bending and extensional stiffness of the host structure and constraining layer separately, in addition to the shear stiffness of the VE layer. This facilitates the incorporation of some anisotropic stiffness effects and a study of its influence on the damping. The Complex stiffness is used to model the damping in individual components. Structural loss factors are obtained as a function of suitable dimensionless stiffness parameters. The useful range of modulus and the thickness of the layers/coatings are identified to obtain desired level of damping for different material loss factors enabling proper choice of the materials and/or thickness of damping treatments. The model can be reduced to represent conventional free or CLD coatings. The proposed model is validated by comparing the results with those from closed form solutions for traditional CLD systems and finite element results for anisotropic systems.