Macromechanical-based fracture assessment supported with acoustic emission of a layered structure with an organic-inorganic sol-gel thin layer

Thin-layer coatings are widely used in industry to enhance structural performance and prevent corrosion-induced degradation. Fracture performance is one of the key aspects investigated to improve interface durability. Nowadays, parameters such as the energy release rate (G) and stress intensity factor (K) are commonly determined using micro- or nanoscale mechanical testing techniques, which require expensive instrumentation. In this study, a macroscopic experimental–numerical investigation was conducted to characterize fracture phenomena at a sol-gel interface using a double cantilever beam (DCB) test on a multilayer system consisting of steel, a coating, and an epoxy resin layer. The experimental campaign was supported by acoustic emission measurements to improve the localization of crack-front propagation and characterize the damage mechanisms occurring within the multilayer system. Based on the experimental results and numerical simulations, a procedure was developed for comparing the fracture toughness of the pure interface with that of the coating-modified interface. Post-failure scanning electron microscopy (SEM) analysis revealed the mixed-mode nature of the damage in the modified material. These findings represent a significant step toward the application of macroscopic mechanical testing for assessing thin-layer coating performance, potentially providing a cost-effective alternative to expensive micro- and nanoscale instrumentation during preliminary testing. The research was supported by the National Science Centre, Poland, under the OPUS + LAP project ‘Research on the influence of self-healing, organic-inorganic sol-gel layers on the corrosion resistance and fatigue of steel in the VHCF range’ UMO-2020/39/I/ST5/03493 and by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project No. 46523772. Calculations have been carried out using resources provided by the Wroclaw Centre for Networking and Supercomputing (http://wcss.pl).