The ability to monitor fractures is based on the integration of PVD thin film sensors and substrates, and the interface stress distribution of the sensor under load which directly impacts the bonding performance. This research analyzes the impact of film elastic modulus and thickness on film-substrate interface stress using the Abaqus software to investigate the influence of PVD film sensor material properties on the film/substrate interface stress distribution. The higher the concentration of interfacial tension, the thicker the layer. The sensor's structural parameters were optimized and significantly enhanced crack detecting sensitivity. The results reveal that the PVD film sensor material can detect structural defects efficiently. The conclusions established in this work have some implications for the optimal design of PVD thin film sensors.

The hole edge of a metal structure is the most likely crack position in an aircraft structure. The quantitative monitoring of a hole-edge crack is important for structural health monitoring. Therefore, this paper presented a grating thin-film sensor based on the potentiometric method. Firstly, the anodic oxidation process was used to prepare thin film on 2A12-T4 aluminum alloy matrix to prevent the aluminum alloy matrix from interfering with the monitoring signal of the sensor. Then the DC superimposed pulsed bias arc ion plating technique was used to prepare the grating thin-film sensor on the surface of the specimen. The output characteristics of the grating thin-film sensor are obtained with its finite element model, and the factors affecting the sensitivity of the sensor are analyzed. Finally, the fatigue crack monitoring tests were carried out to verify the quantitative monitoring capability of the grating thin film sensor. The experimental results show that it is feasible for the grating thin-film sensor to quantitatively monitor the fatigue crack at the hole edge of an aircraft metal structure.