  In disordered, viscoelastic or viscoplastic materials a sample response
exhibits a recovery phenomenon after the removal of a constant load or after
creep. We study experimentally the recovery in paper, a quasi two-dimensional
system with intrinsic structural disorder. The deformation is measured by using
the digital image correlation (DIC) method. By the DIC we obtain accurate
displacement data and the spatial fields of deformation and recovered strains.
The averaged results are first compared to several heuristic models for in
particular viscoelastic polymer materials. The most important experimental
quantity is the permanent creep strain, and we analyze whether it is non-zero
by fitting the empirical models of viscoelasticity. We then present in more
detail the spatial recovery behavior results from DIC, and show that they
indicate a power-law -type relaxation. We outline results on sample-to-sample
variation and collective, spatial fluctuations in the recovery behaviour. An
interpretation is provided of the relaxation in the general context of glassy,
interacting systems with barriers.
