A model to determine the interfacial fracture toughness for chipped coatings

A model is developed to estimate the interfacial fracture energy and interfacial fracture toughness of coated materials on the basis of the buckling load of an axially compressed plate of changing width. The model takes into account the residual stress and the elastic properties of the substrate and is applied to the spalling of coatings during scratch or indentation testing. On the basis of this model the fracture toughness of different organic–inorganic hybrid coatings is determined. The values obtained are a factor 3 to 4 lower than determined previously using a model that takes neither the real shape nor the buckling stress into account.