Viscoelastic

Viscoelastic materials are characterised by the following properties:

• Strain behaviour: time-dependent deformation under load.

• Damping properties: absorption and dissipation of mechanical energy, e.g. from vibrations or impacts.

• Hysteresis: energy loss between loading and unloading due to internal friction.

• Temperature dependence: viscoelastic behaviour changes with temperature; for example, the material becomes softer at high temperatures.

• Frequency dependence: behaviour changes with the loading frequency, e.g. under vibration.

Viscoelastic behaviour can be described by models that take both elastic and viscous components into account:

1. Elastic behaviour

An elastic material stores energy and returns to its original shape when the load is removed (e.g. rubber).

2. Viscous behaviour

A purely viscous material flows under load and does not return to its original shape (e.g. honey).

3. Combination: viscoelasticity

Viscoelastic materials behave like a mixture of an elastic solid and a viscous liquid. This can be described by mechanical models such as the Kelvin-Voigt model or the Maxwell model.

Typical materials with viscoelastic properties are:

Material	Properties	Typical applications
Rubber	High elasticity, good damping	Seals, tyres, vibration dampers
Polymer foams	High energy absorption, flexible	Seat cushions, insulation
Bitumen	Tough and elastic, temperature-dependent	Asphalt, sealants
Silicones	Temperature-resistant, biocompatible	Medical technology, electronics
Polymers such as PMMA	Transparency, good mechanical properties	Lenses, protective panes

Because of their special properties, viscoelastic materials are indispensable in many industries:

Automotive industry

• Tyres: optimum interplay of elasticity and damping for traction and comfort.

• Vibration dampers: reduction of vibration and noise.

Medical technology

• Prostheses: materials with viscoelastic properties offer comfort and stability.

• Orthopaedic mattresses: viscoelastic polymer foams adapt to the body.

Construction industry

• Vibration isolation: materials for damping shocks and vibrations in buildings.

• Sealants: elastic and resistant to movement and stress.

Electronics

• Shock protection: protection of sensitive components against mechanical loads.

• Thermal pads: heat dissipation combined with elastic conformity.

Viscoelastic materials offer numerous advantages:

• Effective damping: absorption of vibrations and impacts.

• Adaptability: combination of flexibility and stability.

• Longevity: high resistance to fatigue and stress.

• Wide range of applications: from low to high temperatures and loads.

Despite their advantages, there are also challenges:

• Temperature dependence: the properties change greatly with temperature.

• Long-term deformation: under constant pressure, viscoelastic materials can creep.

• Costs: high-performance materials can be expensive.

• How do viscoelastic materials differ from purely elastic ones? Viscoelastic materials show time-dependent deformation, while elastic materials return to their original shape immediately.

• Which factors affect viscoelastic behaviour? Temperature, duration of load, loading frequency and material composition are decisive factors.

• In which applications is viscoelastic behaviour particularly important? In applications such as vibration damping, shock absorption and medical prostheses.

• Are viscoelastic materials recyclable? That depends on the material. Some polymers can be recycled, others, such as chemically crosslinked elastomers, only to a limited extent.

Viscoelastic materials combine the advantages of elastic and viscous materials and offer unique properties that make them indispensable in many industries. Their ability to absorb energy while providing stability and flexibility makes them ideal for applications such as vibration damping, shock protection and medical devices. Despite some challenges, their importance in materials research and application is undisputed.