Fatigue behavior of externally bonded and hybrid-bonded carbon fiber reinforced polymer–to–concrete joints

Abstract

Although the bond behavior and failure modes of externally bonded reinforcement (EBR) fiber-reinforced polymer (FRP) and hybrid-bonded (HB) systems on concrete have been widely investigated under quasi-static loading, their performance under fatigue loading remains insufficiently understood. Existing research on RC structures strengthened with carbon FRP (CFRP) under cyclic loading has predominantly focused on demonstrating improvements in fatigue life. However, far less attention has been given to examining the bond behavior and the rate of debonding growth, factors that are critical to ensuring the long-term effectiveness and durability of externally bonded CFRP systems. This study experimentally examines the performance of EBR and HB CFRP-to-concrete bonded joints subjected to cyclic fatigue loading. The investigation focuses on the progression of fatigue-induced damage in bonded joints tested under direct pull-out conditions, using CFRP laminates exposed to different maximum cyclic load levels (relative to the static failure load) while keeping a constant load ratio. Under fatigue loading, interfacial debonding between the CFRP laminate and the adhesive was observed, whereas quasi-static tests typically resulted in cohesive failure within the concrete. Results also revealed that increasing the maximum cyclic load markedly accelerated the rate of debonding propagation

The authors acknowledge the support provided by the Spanish Ministry of Science, Innovation and Universities (MICIU/ AEI) through projects PID2020-119015GB-C22/MICIU/AEI/10.13039/501100011033 and TED2021-132198B-I00/ MCIN/AEI/10.13039/501100011033, UE; L.C. acknowledges the grant RYC2021-032171-I funded by MCIN/AEI/ 10.13039/501100011033 and by “European Union NextGenerationEU/PRTR. The authors wish to acknowledge the support of S&P Clever Reinforcement Ibérica Lda for supplying the laminates and the epoxy adhesive used in this study. Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier