Axisymmetric adhesion tests of soft materials

We describe a general, linearized fracture mechanics analysis for studying the adhesive properties of elastic, low modulus materials. Several adhesion tests are described, but all involve an elastic material which is brought into contact with a rigid surface along an axis of radial symmetry. Relationships between the load, displacement, and radius of the circular contact area between the two materials are described. These relationships involve the elastic modulus of the compliant material, the energy release rate (or adhesion energy) and various parameters which characterize the geometry of interest. The ratio of the contact radius to the thickness of the elastic material is shown to be a particularly important parameter. After reviewing some general concepts relevant to the adhesion of soft polymeric materials, we describe the fracture mechanics analysis, and provide examples from our own work on the adhesion of elastomers, thermoreversible gels and pressure sensitive adhesives.