Correlated heterogeneous deformation of entangled fiber networks.

We study the deformation of a network of entangled non-cross-linked semiflexible fibers subjected to compression. We show that the deformation is intermittent, heterogeneous, and dominated by the occurrence of avalanches. Avalanches imply relative fiber sliding and rearrangement and lead to a serrated stress-strain curve. A large fraction of the fibers in the system contribute to an avalanche, and the amplitudes of the sliding events are correlated spatially. This phenomenon is qualitatively similar in systems with and without friction between fibers and is not due to frictional stick slip.