Damage Formation and Performance Degradation of CFRP Bolted Joints Under Thermo-Oxidative Aging Process

Abstract Carbon fiber reinforced polymer (CFRP) is widely used in aerospace due to its excellent mechanical properties, and the corresponding high-efficiency, high-strength joining techniques have become a key research focus. Among various factors influencing the failure mechanisms and residual life of CFRP joints, the actual service environment plays a crucial role. In this study, the damage formation and performance degradation of CFRP bolted joints under thermo-oxidative aging condition were investigated. Experimental results demonstrate that, even in the absence of external loads, a thermo-oxidative environment can lead to material internal damage within the jointed zone. The difference in the coefficients of thermal expansion between the fibers and matrix can also lead to the appearance of matrix damage and delamination at the entrance and exit of the joining holes. In addition, From the experimental results, it can be seen that thermo-oxidative ageing has a significant effect on the tensile load-bearing properties of the joining structure, and with the increase in ageing temperature up to 150℃, the load-bearing stiffness and strength of the joining structure decreases by up to 34.8% and 23.1%, respectively. These findings highlight the impact of thermo-oxidative aging on the integrity and performance of CFRP bolted joints, emphasizing the need to account for environmental degradation in the design and durability assessment of aerospace composite structures.