Combined effects of seawater ageing and fatigue loading on the bearing performance and failure mechanism of CFRP/CFRP single-lap bolted joints

The aim of this paper is to investigate the combined effects of seawater ageing and fatigue loading on the bearing performance and failure mechanism of CFRP/CFRP single-lap bolted joints. The bolted joints with an interference fit size of 1.15% were prepared and then immersed in artificial seawater (50 °C-3.5% NaCl solution) for 7 months. After that, fatigue loads were further applied to the unaged and aged joints. Finally, single-lap bearing tests were carried out to evaluate the bearing performance of seawater aged and fatigue load treated joints. Scanning electron microscope (SEM) was used to analyze bearing failure morphology. The experimental results showed that the ultimate bearing load of joints suffered the single effect of seawater ageing decreased exponentially with the increase of ageing time, while the joints suffered the combined effect of seawater ageing and fatigue loading decreased linearly. Moreover, compared with the single effect joints, the bearing capacity of combined effect joints showed a significant improvement. Furthermore, the failure mechanism of single effect joints was mainly the shearing fracture in bearing zones, and such shear angle increased with ageing time. However, the failure mechanism of combined effect joints was changed to be delamination in bearing zones.