While dynamic contacts to elastic materials are reasonably well understood, contacts to viscoelastic materials are poorly understood. There is very little quantitative data and, until quite recently, there were no theoretical models including both viscoelastic response and adhesion. This has changed. Research by graduate student Manish Giri has confirmed new theoretical models by C.-Y. Hui and coworkers and by K.L. Johnson. The measurements were made on the surfaces of bulk samples of styrene-butadiene latex films, which are important in paints and paper coatings.
Current activity focuses on thin films, composite materials, and surface modified materials.
The long-range goal is to make contact mechanics a reliable quantitative tool for characterization of complex surface systems such as biomaterials. We are also interested in applications to Paper Coatings . Processes that occur just at the onset of sliding are not understood nor is the role of adhesion. Research by graduate student Eugeniu Popescu will measure the forces and displacements that occur just at the onset of sliding. These measurements are aimed at clarifying the role of microslip phenomena and to test recent theoretical models by by J.A. Hurtado and K.-S. Kim .