Static/fatigue response and degradation behaviors of CFRP/Ti bolted joints under salt-fog and ultraviolet synergistic marine environment

The complexity and uncertainty of the mechanical response behaviors of the bolted joints formed by carbon fiber reinforced polymer composites (CFRP) and titanium alloy (Ti) under complicated marine environment are serious challenges for their continuous and reliable service. This paper conducted comprehensive experimental research to characterize the static/fatigue response and degradation behaviors of CFRP/Ti bolted joints after salt-fog & ultraviolet synergistic environment aging. The load-displacement and strain properties during loading process, and the failure mechanisms were analyzed to identify the mechanical performances evolution of the joints. The results show that the structural damage and instability mechanisms are significantly influenced by the evolution of the contact state around the overlapping area and the composite materials degradation. More serious composites delamination occurs during loading process after aging, and the effect of friction energy dissipation to offset applied load decreases, leading to the failure mode evolves from bolt fracture to hole crushing. In addition, the fatigue life data were analyzed mathematically to reveal the evolution law of fatigue life with aging time and loading level, and two-parameter Weibull distribution was employed to study the fatigue life under different reliability levels.