Effect of elevated temperature on failure behavior of hybrid bolted-bonded joints in composite structures

Experiments and simulations were conducted to investigate the load transfer mechanism and failure modes of a double-bolt single-lap hybrid bolted-bonded joint between glass fiber reinforced polymer (GFRP) plain weave laminates and an aluminum alloy plane under high-temperature conditions. The experimental aspect involved conducting tensile failure tests on hybrid bolted-bonded joints under high-temperature conditions of 80℃, and comparing them with three other working conditions: Hybrid bolted-bonded joints at room temperature, high-temperature bolted joints, and room temperature bolted joints. Failure characteristics at macroscopic and microscopic scales of the hybrid jointed structure were characterized by means of 3D-DIC and SEM. The numerical simulation involved the development of a progressive damage failure model based on the LaRC failure criterion to accurately depict the evolution of in-plane failures. Additionally, cohesive elements were incorporated between plies to effectively simulate delamination behavior. The results indicate that the hybrid bolted-bonded joint exhibits an increase in ultimate load capacity compared to a bolted joint at both room temperature and elevated temperature, with enhancements of 9.2% and 4.0%, respectively. However, it is noteworthy that the ultimate load capacity of the hybrid bolted-bonded joint specimens is reduced by 17.8% in the elevated temperature environment. The hybrid bolted-bonded joint mitigates stress concentration phenomena during the early stages of loading. However, noticeable stress concentrations occur on the surface under temperature-induced loading after premature adhesive failure. The ultimate failure modes include not only the static cross-sectional tensile failure observed in ambient conditions but also compression failure induced by bearing effects. In this scenario, the failure mode aligns with that of a pure bolted connection. The developed numerical simulation model can accurately predict the failure modes and evolution process of the structure, enabling a comprehensive analysis of the load transfer mechanism and failure patterns in hybrid bolted-bonded joint structures.