Effect of postcuring immersed in water under hydraulic pressure on fatigue performance of large-diameter pultruded carbon/glass hybrid rod

A pultruded carbon fibre core (CFC) and glass fibre shell (GFS) hybrid fiber reinforced polymer (HFRP) rod with the diameter of 19 mm was developed. It was kept immersed in water in a self-designed pressure chamber device with adjustable hydraulic pressure (20 MPa); after immersion, the tension-tension fatigue performance was measured at stress levels of 41.7%, 33.4%, and 25.0%. Significant postcuring of resin was observed, resulting in the increase in T _g s for the core and shell layers. There was no significant decrease in the tensile strength of the hybrid rod. The fatigue failure of the hybrid rod was accompanied by debonding of CFC/GFS interface, redistribution of cyclic load, and catastrophic splitting or bursting of GFS. The immersion in water under hydraulic pressure led to a significant increase in fatigue life. The increase in the fatigue life was because of the improvement in interface bonding strength and toughness of the resin owing to the postcuring of the resin. After fatigue, significant degradation in the residual interface bonding strength was observed for the hybrid rods.