Viscoelastic damping treatments on microtextured substrates

• Autor(a) principal: Marques, André Pereira
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/36210
• topic: Passive damping treatments; Viscoelastic damping treatments; Optimisation of viscoelastic damping treatments; Finite element method; Modal strain energy; Chessboard interface

Machines, structures supporting sensitive systems, and lightweight structures used, for instance in aircraft, are all susceptible to the efficiencyreducing effects of vibrations. Recent advancements in lighter materials and assembly processes come at the cost of decreased mechanical connections which are important to dissipate the energy stored by vibration. With this in mind, vibration control of light and stiff structures is often achieved through passive damping treatments employing viscoelastic materials. The addition of viscoelastic layers exhibiting significant material damping allows the structures to dissipate deformation energy as heat, especially when these layers are integrated into two layers made of a highstiffness material. Therefore, the main objective of this work is to analyse the effects of functional and indented texture applied to the inner surface of the external structures that accommodate a waved damping layer between the sandwich structure. Thus, it takes advantage of the high-shear strain created due to the motion of the adjacent layers when under vibration, which maximises the deformation imposed on the viscoelastic layer, hence promoting heat loss and, consequently, improving the damping characteristics of the viscoelastic treatment. In view of this goal, this study is conducted and oriented towards the numerical modelling of these treatments using five variable parameters to define the textured configuration. To this effect, the spatial model and the mesh are created based on a 3D solid hexahedral finite element using Matlab. Then, a normal modes analysis combined with the modal strain energy method is carried out using Femap with Nx Nastran software. In the end, the dynamic response of the first mode of each configuration is evaluated and compared to each other by means of a parametric study that provides a thorough analysis of the design variables. As far as the different metrics of indentations are concerned, there is no oneway path that proves to be unique to reach the highest efficiency. Thus, when designing viscoelastic damping treatments based on configurations with integrated layer damping and indentations, different combinations between the parameters must be analysed. Even though, numerical results indicate that, for thicker core symmetric treatments, the waved pattern of the viscoelastic material layer promotes damping efficiency and reduces the decoupling effect that characterises this damping configuration.