  An elastic membrane that is forced to reside in a container smaller than its
natural size will deform and, upon further volume reduction, eventually
crumple. The crumpled state is characterized by the localization of energy in a
complex network of highly deformed crescent-like regions joined by line ridges.
Previous studies have focused on the onset of the crumpled state by analyzing
the mechanical response and stability of a conical dislocation, while others
have simulated the highly packed regime neglecting the importance of the
connectivity of the membrane. Here we show, through a combination of
experiments, numerical simulations, and analytic approach, that the emergence
of new regions of high stretching is a generic outcome when a self avoiding
membrane is subject to a severe geometrical constraint. We demonstrate that, at
moderate packing fraction, interlayer interactions produce a response
equivalent to the one of a thicker membrane that has the shape of the deformed
one. Evidence is found that friction plays a key role stabilizing the folded
structures.
