Visualizing Contact Area Growth in Frictional Interfaces

Seemingly static interfaces between two solids are in fact dynamic. These multicontact interfaces (MCIs) exert enormous stresses on tiny contact areas, causing time-dependent deformation, also known as aging. Though these phenomena are ubiquitous in engineering and the sciences (e.g from micromachines to plate tectonics), their underlying mechanisms are not yet well understood. Quantitative, 2D measurements of the real contact area between a polymer solid and a glass plate are obtained over a variety of normal loads and time steps. By varying geometric and elastic properties of our samples, we induce variations in the 2D structure of contact growth, which give insight into the mechanisms that produce aging in frictional interfaces.