Temperature effects on bonding performance of near-surface-mounted CFRP concrete interfaces: Experimental and finite element studies

Near-surface-mounted (NSM) CFRP-concrete systems are increasingly used for structural strengthening, yet their long-term performance under temperature variations remains inadequately understood. This study investigates the effects of curing and service temperatures on the interfacial bond performance of NSM CFRP-concrete systems. Single-shear pull-out tests were performed on C40 concrete prisms bonded with 16 mm × 2 mm CFRP strips using Sikadur-30 CN epoxy, with curing and testing temperatures ranging from 20 °C to 100 °C. Nonlinear spring-based finite element models were developed to simulate temperature-dependent bond-slip behavior. The results show that increasing the test temperature from 20 °C to 80 °C reduces the peak interfacial shear stress by 46.7 %, and the failure mode shifts from cohesive concrete failure to CFRP-epoxy debonding. High-temperature curing at 80°C improves the epoxy’s glass transition temperature ( T g ) and cross-link density, resulting in 8.1 %–16.67 % higher failure loads at elevated temperatures. Elevated temperatures also decrease the ultimate load capacity and flexural stiffness of CFRP-strengthened beams by 14.3 % and 35.8 %, respectively. The developed temperature-dependent bond-slip models and finite element framework enable accurate prediction of NSM CFRP system performance under thermal effects. These findings emphasize the need for temperature-adaptive design strategies in NSM CFRP applications and provide a theoretical basis for future multi-physics modeling.