Mechanical modelling and experimental identification of the model parameters of multilayer coated specimens for high damping industrial applications

Coating technology may be adopted to produce composite mechanical components with high vibration damping behavior, but thick coating layers, significantly modifying the geometry and the mechanical properties of the component, may generally result. An alternative approach is to use multilayer coatings designed to maximize the interlaminar dissipative actions. By adopting this approach relatively thin coatings may result, while the composite component geometry, stiffness and strength properties do not greatly change with respect to the uncoated solution. Preliminary experimental tests made by our research group on multilayer coating applied by means of different technologies such as reactive plasma vapour deposition (RPVD), anodization, screen printing of inhorganic polymer and cianoacrilate based coatings, showed some interesting but still not fully satisfying results. In order to reduce time and costs of the development process of new coating solutions a multi-layered beam model was proposed for numerically simulating the response of a composite beam specimen, taking into account of the slipping occurring at the interface between the layers and of distributed dissipative actions modelled by means of a complex interlaminar impedance. By adopting a discretization procedure based on a spectral approach, a linear, second order system of discrete equations result, involving complex Hermitian matrices. The damping behaviour of the composite beam can be evaluated by means of different estimators based on the complex eigenvalues resulting from the eigenproblem associated to the system homogeneous equations (free vibration) and on a real, frequency dependent, normalized functional based on the system frequency response function. Nevertheless, since the application of this model strongly depends on the values of the interface parameters, a numerical identification procedure based on experimental tests done on reference bilayer beam specimens is presented, and results are critically discussed. Some interesting results are obtained by virtual prototyping by means of the proposed model and the interface identified parameters. New multilayer architectures showing useful damping behaviour, are obtained and experimentally validated as well, and presented herein.