What is viscoelasticity?
When a force is applied to a material, it causes the material to deform. This deformation can take one of two extremes – pure elastic deformation (e.g. a spring) or pure viscous flow (e.g. oil).
The force causes the elastic material to instantly deform by a set amount, and the viscous material to flow for the whole time the force is applied. When the force is removed, the elastic material instantly returns to its original state, whereas the viscous material does not recover at all.
Elastic behaviour is usually caused by the bonds stretching between atoms (which is instant). Viscosity is caused by atoms or molecules moving past each other, which takes time but is also not easily reversed, unlike elasticity.
