Tension–Tension Fatigue Damage Evolution and Failure Mechanism of Carbon/Glass Hybrid Fiber Composite Rods for Mooring Cables

Fatigue failures of major structural cables threaten engineering infrastructure. Fiber‐reinforced polymer (FRP) composites are promising alternatives to steel cables, while hybrid composites can overcome the limitations of single‐fiber systems and promote applications in super‐long‐span and high‐tonnage cables. In this study, carbon/glass hybrid fiber‐reinforced composite (C/GFRP) rods were fabricated by pultrusion. Static mechanical tests were conducted to evaluate strength and interfacial bonding, and tension‐tension fatigue behavior and mechanisms were investigated under different stress ratios and levels. The tensile strength and flexural modulus were 1945.7 MPa and 167.3 GPa, respectively, while the short‐beam shear and in‐plane shear strengths were 68.4 and 43.8 MPa, indicating excellent interfacial bonding. At high stress levels, fatigue damage initiated from carbon‐fiber fracture in the skin layer, causing brittle burst failure. At low stress levels, damage initiated from debonding at the carbon‐fiber skin/glass‐fiber core interface, causing overall splitting failure. This difference between interface‐matrix‐dominated damage at low stress and fiber‐fracture‐dominated damage at high stress reflected the energy‐threshold effect of fatigue failure. Therefore, interfacial bonding of the glass‐fiber core should be enhanced under low‐stress conditions, whereas carbon‐fiber strength uniformity should be improved under high‐stress conditions. Combining a high‐modulus carbon‐fiber skin with a glass‐fiber core significantly enhanced fatigue resistance through low‐stress interface buffering and high‐stress fiber load‐bearing, demonstrating important scientific and engineering significance.