Viscoelastic materials - Reduction of noise and vibrations

Viscoelastic materials are used in all areas of engineering and mechanical systems, from household appliances to space, automotive, aeronautics and civil engineering (bridges, etc.). They are designed to dissipate the mechanical energy of vibrations into heat. In addition to extending the life of structures, they also attenuate noise and vibrations. There are two main classes of viscoelastic materials: polymers (elastomers, plastics, etc.) and ceramics (glass, varnishes, etc.); see reference [5] in the [Doc. N 720] document.

Today, around 30 kilos of this type of material can be found in a car; it is used to "decouple" the engine from the body, in shock absorbers, but also in body sandwich panels (doors, ceiling, trunk) or inside the passenger compartment, including seats. The aim, of course, is to reduce noise and vibrations inside the cabin. Despite weight constraints, this type of material is widely used in the aeronautics industry to insulate electronic and measurement systems, or any other on-board systems that need to be protected from vibration. Still in aeronautics, we can cite applications for these materials in turbine blades and seals, but also in interior trim. The building industry is also an area where viscoelastic materials are increasingly used: for example, roller shutter frames and the shutters themselves, as well as walls and floors, where materials with high viscoelastic properties provide vibration reduction and acoustic insulation.

The following is a non-exhaustive list of elements or applications using viscoelastic materials. Some typical elements are shown in figure 1 of the document sheet [Doc. N 720] :

• motor and machine mountings ;

• seals and drive belts ;

• glazing beads and subsystem fasteners ;

• amortization of metal plates and shells ;

• seat parts and cabin interiors ;

• tires and wheels ;

• tuned damping systems.

The main function of viscoelastic materials is to provide a mechanism for dissipating the mechanical energy of vibrations into heat. As a result, they reduce noise and vibration. However, during the design phase, it is important to understand their influence on the structure. This is a function of the mass of these elements, their geometry, interfaces, the environment and, of course, the dissipation characteristics of the material.

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