Ripplocations: A universal deformation mechanism in layered solids

Layered solids are ubiquitous in nature: from subnanometer graphene and mica layers, to wood, laminated composites, and paperboard at the centimeter scale, to geologic formations at the kilometer range. And while the similarities between the latter two have been recognized [Budd et al., Philos. Trans. R. Soc. A 370,1723 (2012)], what has not is that the same physics applies at the atomic-layer scale of crystalline solids. Herein, using a combination of atomistic simulations of graphite and simple instrumented cylindrical indentation experiments on various layered solids-plastic cards, thin steel, and Al sheets-we show that in all cases, confined buckling results in an instability that leads to the nucleation of multiple, oppositely signed ripplocation boundaries that rapidly propagate away from under the indenter in a wavelike manner. Crucially, upon unloading, they disappear, after dissipating considerable amounts of frictional energy. Understanding ripplocation nucleation, self-assembly, and propagation is fundamental to understanding the deformation of most layered solids.