Development of bending tests for near shear mode interfacial toughness measurement of EB-PVD thermal barrier coatings

Some results on the TBC adhesion energy are presented, relating to both the temperature and the time-of-aging for relevant mode mixity consistent with the spallation configurations observed from feedback on ex-service blades. The effect of the residual stresses induced during thermal cycling is considered here, in order to derive the intrinsic critical energy release rate. The whole set of data enables a description to be made of the intrinsic interfacial toughness decreasing under both thermal aging and mechanical loading. Finally, an energetic approach is used to compare this intrinsic interfacial toughness to the elastic stored energy during thermal cycling, in order to assess the lifetime corresponding to spontaneous spallation.