14. Polymer Viscoelasticity Available to Purchase

Under normal conditions the response of metals and ceramics to external stimuli such as stress or deformation is instantaneous and time-independent, so that a constant load results in a constant, time-independent deformation. For these materials the theory of elasticity provides an adequate model for characterizing mechanical properties and mechanical design. In contrast, polymeric materials exhibit time-dependent behavior for the understanding of which linear viscoelasticity theory, discussed in Chapter 7, provides the simplest model. In this class of materials, the deformation can continue to change even under a constant load. Not only does this make materials characterization more difficult, it requires a complete rethinking of mechanical design methodologies that have yet to be adequately defined.