An inquiry into the uncertainty mechanism: The influence of the number of layers in multilayered damping materials on composite loss factor

Abstract Layered design is an important method for improving the loss factor of damping materials. However, the composite loss factor does not increase with the increase of the number of layers of the damping material. In response to this issue, this paper investigates the mechanism by combining experimental and simulation analyses. First, for the damping material itself, the relationship between the material loss factor and the number of damping layers was studied based on dynamic mechanical analysis. Second, for the composite structure of damping material and substrate, the relationship between the composite loss factor and the number of damping layers of the free damping structure was obtained by the cantilever resonance method, and the influence of material and structure parameters on the composite loss factor was clarified by finite element analysis. Finally, for aiming at the composite structure of damping material with constraint layer and substrate, the mechanism of the influence of the number of layers of layered damping material on the uncertainty of the composite loss factor was further investigated and discussed. The results indicated that for free damping structures, the composite loss factor increases with the increase of the number of damping layers only when the elastic modulus of the damping layer is similar to that of the substrate. For constrained damping structures, only when the constraint layer is relatively thin and has a certain amount of density and modulus, the composite loss factor of the constrained damping structure increases as the number of damping layers increases. Highlights The mechanism by which the number of layers of damping material affects the composite loss factor has been clarified. The composite loss factor does not necessarily increase as the number of layers of damping material increases. The composite loss factor of a free damping structure is mainly influenced by the Young's modulus of the damping layer. The composite loss factor of constrained damping structures is mainly influenced by the thickness, density, and modulus of the constrained layer.