Contact-driven delamination and spalling of coatings due to cyclic shock heating

A new debonding mechanism taking into account crack face contact caused by a thermal gradient during laser heating is considered. The contact renders double influence on the energy release rate G: it leads to sharp increase of G at convergence of two cracks and decreases steady-state value of G. The first feature can explain the laser-induced spalling of thermal barrier coating under combined action of sintering and heating. The inhomogeneous temperature through coating thickness under laser heating can induce contact-driven debonding leading to the spalling under convergence of two cracks. The loading conditions of contact occurrence are derived. The simplified models of contact-driven debonding are proposed and compared with finite element solution.