Carbon Fiber Reinforced Plastics (CFRP) are critical for load-bearing structures like wind turbine blades and aircraft components, where bolted joints offer high reliability. However, the viscoelastic/viscoplastic nature of CFRP resin causes time-dependent clamping force loss, potentially compromising joint integrity. This study evaluates long-term durability of bolted CFRP joints and clarifies clamping force reduction mechanisms through experiments and simulations. Quasi-isotropic laminates (45/0/45/90₃s) underwent torque preloading (3N·m) and thermal cycling (25-120°C) to isolate viscoelastic creep from viscoplastic deformation. An accelerated testing methodology (ATM) based on resin viscoelasticity predicted long-term behavior. Relaxation tests at multiple temperatures enabled master curve development for relaxation modulus, supporting service-life predictions. Statistical analysis quantified performance variability and established reliability-based design criteria. Simulation models focused on predicting clamping force evolution over time. Findings reveal time-dependent failure mechanisms in CFRP bolted joints and provide guidelines for designing durable connections in critical composite structures, enhancing long-term durability prediction methods.
TANIYAMA et al. (Wed,) studied this question.