Wrinkles, folds, and ripplocations: Unusual deformation structures of confined elastic sheets at nonzero temperatures
We study the deformation of a fluctuating crystalline sheet confined between two flat rigid walls as a simple model for layered solids where bonds among atoms within the same layer are much stronger than those between layers. When subjected to sufficiently high loads in an appropriate geometry, these solids deform and fail in unconventional ways. Recent experiments suggest that configurations named ripplocations, where a layer folds backwards over itself, are involved. These structures are distinct and separated by large free-energy barriers from smooth ripples of the atomic layers that are always present at any nonzero temperature. We use Monte Carlo simulation in combination with an umbrella sampling technique to obtain conditions under which such structures form and study their specific experimental signatures.