Nucleation and growth of cavities in soft viscoelastic layers under tensile stress.

The process of growth of an individual cavity in a viscoelastic adhesive layer has been investigated experimentally. The formation of cavities was caused by the application of a negative pressure on a very confined layer with a flat-ended probe. The cavities appeared in the bulk of the adhesive layer and were observed for a range of values of applied stress approximately ten times higher than the shear modulus of the adhesive layer. Depending on the loading rate, the shape of the growing cavity changed from a flat disc to a more spherical shape. Furthermore, the growth rate of the cavity radius was consistent with a constant strain rate at the edge of the cavity, which suggests a constant level of stress at the edge of the cavity.