<p>The paper focused on the fatigue testing of thin-walled composite structures with notches. The fatigue experiments were supported by non-destructive diagnostic techniques, including thermography, acoustic emission, and digital microscopy. The study analysed the influence of notch geometry on the initiation and evolution of damage in CFRP (carbon fiber reinforced polymer) specimens with a [0/45/-45/90]_s lay-up. All specimens were tested under identical fatigue loading conditions. Within the scope of the research, quantitative characteristics of thin-walled structures under fatigue loading were developed, and the recorded damage mechanisms were examined qualitatively. The combination of interdisciplinary research methods made it possible to carry out a thorough analysis of composite structure behaviour. Tests involving the complete failure of the specimens were not conducted. Instead, the study focused on the detection and monitoring of early stages of damage within the low-cycle fatigue regime. The application of coupled diagnostic methods for detecting and monitoring fatigue damage made it possible to investigate the differences in damage initiation and development between specimens with U-shaped and V-shaped notches.</p>