Buckles in adhering elastic films and a test method for adhesion based on the elastica

A buckled elastic film that adheres to a flat rigid substrate everywhere except at the buckle takes up a characteristic shape, known as an elastica. The shape depends on the bending stiffness of the film and the strength of adhesion; the buckle spreads outwards as adhesion decreases. Two arrangements of an initially buckled film are suggested as the basis of possible methods for measuring adhesion. The tests are simple to perform and seem particularly useful for long-term studies. However, the theoretical treatment requires that the film be substantially elastic in bending. Adhesive tapes may show this feature because of the dominant effect of a stiff elastic backing. If not, the tape could be adhered to a stiff and elastic backing film (for example, of polyester or spring steel) to meet this theoretical requirement.