Micromechanics model for the detachment of residually compressed brittle films and coatings

The durability of residually compressed coatings, particularly thermal barrier coatings (TBCs), is governed by events occurring at the interface with the substrate. In general, failure involves the sequential nucleation growth and coalescence of separations in the presence of imperfections and defects. The growth and coalescence phases are analyzed. Remnant ligaments are expected from the mechanics. These allow the coating to remain attached to the substrate, even when interface separation is profuse. Detachment happens when transverse loads develop. Critical values of these loads are calculated and their implications discussed.