Description
Ultra-high strength steel (UHSS) with exceptional mechanical properties is gaining widespread use across various industries. However, research on strengthening UHSS with surface cracks using Carbon Fiber Reinforced Polymer (CFRP) is limited.
Accordingly, a series of CFRP strengthening UHSS Q890 and Q960 experiments with surface cracks are carried out under fatigue loading. Two loading programs, the maximum stress equal to half yield strength fy and 200 MPa, are designed. Surface cracks at the weld root were pre-cracked, and a single layer of CFRP was applied adhesively to both sides of the butt-welded UHSS. First, the results show that when subjected to a maximum stress of 0.5fy, the fatigue life decreases as the steel grade increases. The strengthening effect is 1.07 and 1.34 times for Q890 and Q960, respectively. Second, when subjected to a maximum stress of 200 MPa, the fatigue life decreases as the steel grade decreases. Excellent strengthening effects of 1.89 and 2.60 times were obtained for Q890 and Q960, respectively. Finally, it is observed that CFRP delamination and rupture are the main fracture modes.
