Temperature effect on the fatigue properties of CFRP bolted joints by combining DIC, AE and IRT techniques

This research examines the temperature effect on the fatigue performance of composite bolted joints by combining digital image correlation (DIC), acoustic emission (AE), and infrared thermal imaging (IRT) techniques. A novel method for calculating the sentry function during fatigue is proposed. The temperature effect on stress evolution and fatigue-induced temperature rise in joints is revealed. Experimental results indicate that the displacement amplitude and hysteresis energy of the joints exhibit typical "bathtub curve" characteristics during fatigue, with total hysteresis energy effectively characterizing the joints’ fatigue life across varying temperatures. Analysis of changes in the sentry function reveals the initiation and development of fatigue damage within the joints at different temperatures. Furthermore, the fatigue stress level significantly alters temperature rise patterns during joint fatigue. The integration of AE, DIC, and IRT techniques, from the perspectives of acoustics, optics, and thermal analysis, effectively elucidates the fatigue damage evolution mechanisms in the joints. This work contributes to the optimization of composite joint design and durability assessment in engineering applications, particularly in environments subjected to temperature fluctuations.