# Viscoelastic

From Soft-Matter

## Definition

A substance that displays behavior that is both viscous and elastic is said to be **viscoelastic**. In this sense, viscoelastic materials are said to be a combination of the ideal (elastic) Hookean solid and the (viscous) Newtonian liquid, along with a time a dependence.

## Hookean Solid

A Hookean solid is one that displays perfectly elastic behavior. This corresponds to the fact that an applied shear stress produces a shear strain in response. Recall that the shear stress (<math>\sigma</math>) is given by the applied force over the area which the force is applied, namely <math>\sigma = F/A</math>, and the shear strain (<math>e</math>) is given by <math>e = \delta x/y</math>.