The failure mechanisms of TBC structure by moiré interferometry

In order to study the interface failure process and the mechanical properties of thermal barrier coatings (TBCs), the moiré interferometry technique is used to measure the deformation fields of the TBC specimen subjected to three-point bending load. By changing the object lens in the moiré interferometer, both the macro-scale and micro-scale deformation fields can be measured. In the measurement, a cross type moiré grating with frequency 1200 lines/mm is replicated to the TBC sample. The interface moiré patterns at different load parameters can be obtained with the moiré interferometer. And the corresponding displacement and strain distributions are calculated using the moiré patterns. Besides, with aid of the experimental results from moiré interferometry, crack opening displacement (COD) and J-integral of the TBC specimen can be measured. Moreover, the initiation and propagation of the crack in TBCs are observed using scanning electronic microscope and optical microscope, respectively. The failure mode of the TBC is summarized.