Surface wrinkling of two mutually attracting elastic thin films due to vander Waals forces

This article studies surface instability of two mutually attracting elastic films due to van der Waals forces under plane strain conditions. The analy sis is based on an approximate method which reduces a two-dimensional probl em of an elastic film to a one-dimensional surface problem. This method is much simpler than the conventional method and allows one to easily identify the critical value of the interaction coefficient and the surface instabil ity mode. The accuracy of this method is demonstrated by the excellent agre ement (with relative errors less than 5%) between the predicted results and the known exact data for a special case of an elastic film interacting wit h a rigid flat surface. The incompatibility of the individual fundamental m odes of two elastic layers with unequal thickness results in two distinct m etastable instability modes when the thickness ratio exceeds a critical val ue, in contrast to the uniqueness of the surface instability mode of an ela stic film attracted to a rigid flat surface. This nonuniqueness of the meta stable instability modes would cause complex surface instability phenomena of two interacting elastic films (such as jump between the two instability modes). (C) 2001 American Institute of Physics.