How the Cookie Sheet Crumples:
New Insights into Material Deterioration and Failure

Top: Experimental images of crumpled sheets (blue + curvature, red—curvature). Bottom: Simulation of elastic sheet crumpling exhibiting agreement with the behavior in real sheets.

Every child has experience with crumpling paper. In a Seed Project at the Harvard MRSEC, Amir and Rycroft have been studying this process using a combination of analytic and computational methods. Rubinstein has performed experiments where sheets are systematically crumpled (top) and made a surprising discovery – the amount of creasing can be described by a simple relation. To further understand the crease patterns after successive crumpling, Rycroft uses machine learning to try to predict where the new creases will form. Amir and Rycroft are exploring an elastic model (below) that shows remarkable agreement with the real sheets. While such crumpling is familiar as a common experience, successively deforming an object is the process of fatigue testing. This work may help predict the deterioration and failure in a wide class of materials.