Étude du comportement d'interface d'une barrière environnementale sur composite à matrice céramique

One of the challenges in aeronautics is to reduce the environmental impact of airplanes. This objective is pursued through the development of alternative solutions to metallic materials such as ceramic matrix composites. For the intended applications, the components are exposed to extremely severe thermomechanical and physicochemical environments (oxidation/corrosion), which can lead to material degradation and limit their lifespan. To protect the ceramic matrix composite (CMC), the components are coated with environmental barrier coatings (EBC) that mitigate the corrosion of the CMC. Understanding the damage mechanisms of EBC on CMC is therefore crucial for the development of carbide-based CMC components.In this context, this thesis focused on the behavior at the interfaces of the different constituents of the system to analyze the adhesion of the coating on the CMC. The aim is, on the one hand, to propose and implement tests at ambient and high temperatures to quantify the initiation and propagation of delamination at the interfaces and to characterize the associated properties, such as the adhesion energy of the coating on the CMC, using various experimental crack-tracking methods based on optical techniques. On the other hand, the goal is to establish a close interaction between the tests and the associated modeling. For this purpose, four-point bending tests were conducted at room temperature and at 1000°C to propagate stable cracks at the interface of the system. Kinematic field measurements through image correlation were used to inform finite element simulations in order to track crack propagation and extract interfacial adhesion energy at the macroscopic scale. These tests and their analysis were used to characterize the propagation phase at both temperatures and to compare the adhesion of pristine systems with systems that had been previously aged in an oxidizing environment. In a second phase, laser bench tests with the presence of thermal gradients within the system allowed for the characterization of the initiation phase. Scanning electron microscope observations, along with the use of thermal cameras and acoustic emission sensors, complemented the experimental database.