Cure Terms Glossary

Viscoelastic

A viscoelastic material has viscous as well as elastic properties. This behaviour may manifest itself in various ways, e.g.,

  • A material, with the appearance of a solid, which cannot maintain a constant deformation under constant stress (i.e. creeps over time),
  • A material, with the appearance of a liquid, which, under flow, can store some of the input energy instead of dissipating all of it as heat (i.e. partially springs back after flow),
  • A material when subjected to a sinusoidally oscillating stress where the resultant strain is neither exactly in phase with the stress (as for a perfectly elastic solid) nor 90° out of phase (as for a purely viscous liquid) but somewhere in between.

Thus if the angle δ is the phase lag between stress and strain.

δ = 0° for perfectly elastic materials
δ = 90° for purely viscous materials
90 > δ > 0° for viscoelastic materials

Another term is elastoviscous, but this is not interchangeable with viscoelastic as it is only used as a term for liquids - i.e. materials more viscous than elastic. Whilst the term viscoelastic can be used to cover all degrees of mixed viscous and elastic character, it can also be reserved as a descriptor for solids - i.e. materials with more elastic then viscous character.