Acoustic emission evaluation of fracture characteristics in thermal barrier coatings under bending

The real-time assessment on the details in damage evolution of thermal barrier coatings (TBCs) is desirable, especially if the key coating performance parameters, such as, the surface and interface fracture toughness, could be accurately characterized. In this paper, the fracture details of as-sprayed and pre-oxidized TBCs under three-point bending are monitored by an acoustic emission (AE) combined with digital image correlation (DIC) methods. The surface and interface toughness of TBCs can be accurately determined on the basis of AE signals and strain images. A linear relationship is found between the energy released from coating failure and that of AE signals, whose slope depends on the fracture modes and properties of TBCs.