Identification of fracture properties at the interface between CMC and EBC at room and high temperatures using full field measurements

The objective of this work is to predict the lifespan of CMC/EBC systems by quantifying interface damage and estimating the interface adhesion energy. Four-point flexural tests were conducted at room temperature and 1000°C. These tests initiated cracks through the thickness of the coating. Then, the crack bifurcated and propagated along the interface. Visible light cameras (monovision and stereovision) monitored these tests to measure kinematic fields via digital image correlation (DIC). The kinematic fields were used to establish a test/finite element (FE) simulation dialogue to estimate the crack tip locations at the substrate/coating interface. Experimental displacement fields are also used as input in FE simulations (applying boundary conditions from DIC-derived fields) to calculate the critical energy release rate at the interface during crack propagation. Initially implemented for room temperature test, these methods are then applied to a high-temperature test. The computed energy release rates for both temperatures indicate higher interfacial fracture toughness at elevated temperatures.