Static failure of hybrid bolted-bonded composite joints in hygrothermal environment

Hygrothermal environment has a significant impact on the safety and reliability of hybrid bolted-bonded composite joints. This study aims to investigate the effects of hygrothermal environment and geometrical parameters on the mechanical properties of hybrid bolted-bonded joints. In this paper, through the static tensile test and SEM scanning electron microscopy of hybrid bolted-bonded joints with different end-to-diameter ratios ( E/D ) and width-to-diameter ratios ( W/D ) under room temperature dry (RTD) and elevated temperature wet (ETW) environments, the change rule of the static strength of the joint and the macro-micro failure form are obtained. A finite element model of the hybrid bolted-bonded joint was established to obtain the initial stress distribution states of different layups and adhesive layers of laminates. The results indicate that the ultimate load of the hybrid bolted-bonded joint increases with the increase of E/D and W/D within a certain range. The ETW environment significantly reduces the ultimate load of hybrid joints. SEM scanning electron microscopy revealed that the compression damage of laminates in the ETW environment was aggravated. The hole edges exhibited an obvious state of matrix fracture and collapse. In the thickness direction, there was an increase in fiber breakage and debonding in the 90° fiber orientation, accompanied by more resin debris.