Memory and aging in the cyclic crumpling of a film*

Many bulk materials can retain memories of their past; rocks and glasses may remember a stress that was previously applied or a temperature at which they were aged. Here we study a thin cylindrical shell under cyclic loading. Whereas previous work focused on the mechanical response of an already-crumpled film [1], we begin with a pristine film and study its route to steady states under a variety of cyclic driving protocols—in effect, converting pristine or lightly-crumpled raw material into a reliable structural component with memory. We combine acoustic, force, and optical measurements to capture reversible and irreversible changes to the folds and ridges in the sheet. Under cyclic axial compression, we see behaviors that are nominally consistent with return-point memory, but with pronounced aging effects—a combination of memory behaviors that may be relevant to other complex condensed matter systems. We also study how these behaviors are modified by introducing torsion of the cylinder as a second driving parameter.

[1] Lahini et al., PRL 118 (2017)