  Soft polymer-based solid materials can be defined as solid materials with
elastic moduli below 1 MPa. In order to obtain such a low modulus while
retaining a solid character, all these materials are based on a network of
fixed points (crosslinks, physical interactions) keeping together a liquid-like
matrix. Since they are not able to flow, very large deformations will lead to
failure by fracture or cavitation. We discuss in this paper new experimental
data suggesting that the growth of a cavity in a soft nearly elastic solid
undergoes a transition from a stress-controlled growth, when the initial cavity
size is larger than Gc/E, to an energy-activated growth, when the initial
cavity size is smaller than Gc/E. The important material length scale Gc/E
represents the ratio between the surface energy necessary to expand the cavity
and the elastic modulus. This energy activated growth regime is due to the
existence of a metastable solution and significantly increases the apparent
cavitation stress for layers thinner than 1000 Gc/E.
