Viscoelastische

Viscoelastische, in English viscoelastic, refers to materials that exhibit both viscous and elastic behavior when subjected to deformation. They respond to stress with a combination of immediate elastic strain and time-dependent viscous flow. The relative contribution of the viscous and elastic components depends on factors such as temperature, time, and the rate of loading.

In viscoelastic materials, characteristic phenomena include creep (gradual deformation under constant stress), stress relaxation (decrease of stress under constant strain), and hysteresis during loading and unloading. The microscopic origin lies in the movement and reconfiguration of molecular chains, cross-links, and network structures, which allow for both instantaneous elastic deformation and slower, irreversible rearrangements.

Common viscoelastic materials are polymers (thermoplastics and elastomers), gels, foams, asphalt, and many biological tissues such as tendons and cartilage. These properties are critical for applications in mechanical design, biomechanics, and material science, where performance depends on both stiffness and damping.

Constitutive models used to describe viscoelastic behavior range from simple mechanical analogs, such as the Maxwell and Kelvin–Voigt models, to more sophisticated representations like the Standard Linear Solid model and complex numerical rheology. Dynamic mechanical analysis and rheometry are standard methods to characterize storage and loss moduli, damping, and time-temperature dependence.

Viscoelastic properties are temperature-dependent, often analyzed with the time-temperature superposition principle to predict behavior over a broad time or frequency range. Understanding viscoelasticity is essential for predicting material performance under real-life loading conditions.