Tear Phenomena around Solid Inclusions in Castable Elastomers

Adhesion studies on spherical particles imbedded in elastomers have shown that cohesive failure of the binder phase always precedes dewetting. The latter is a sudden and irreversible process resulting in permanent damage to the system. Cohesive failure manifests itself in the formation of a number of small holes near the surface of the filler particle. The stress σ′ causing these holes is well defined and depends only on the elastic modulus E of the binder: σ′=E/2+C. The further propagation of these initial tears depends on the consistency of the boundary layer surrounding the solid inclusion. In case of no modulus gradient or a softer boundary layer, tear propagation leads to the complete separation of the elastomeric binder from the particle. High modulus layers, which are linked to the polymeric matrix by primary chemical bonds, prevent a dewetting. It is shown that the complex response of filled elastomers can be explained in terms of the above results.