Flexural behavior of reinforced concrete beams strengthened with hybrid carbon-PET FRP laminates

This paper presents an experimental study of the flexural performance of reinforced concrete (RC) beams externally bonded with hybrid fiber-reinforced polymer (FRP) laminates made of carbon and polyethylene terephthalate (PET) fibers. Ten beam specimens were subjected to four-point bending tests, with a focus on assessing the effects of the stacking sequence and the elastic modulus of hybrid carbon-PET FRP laminates on the flexural performance of the strengthened beams. The failure modes, load-bearing capacities, displacement ductility of the specimens and strain distributions in the FRP laminates were examined and discussed. The experimental results showed that the load-carrying capacities of the FRP-strengthened specimens were significantly increased by 10.18-27.98%, while the displacement ductility decreased by 51.36-77.85%. The peak load and ductility of the beam specimens strengthened with PC (i.e., PET-C FRP) and CPC (i.e., C-PET-C FRP) stacking sequences were higher than those of their counterparts strengthened with two or three layers of hybrid FRP laminates. The accuracy and reliability of the calculation methods specified in ACI 440.2R-17, CNR DT 200 R1/2014 and GB 50608-2020 for estimating the flexural strengths of the strengthened RC beams were evaluated through a comparison of theoretical predictions with experimental results. The average predicted-to-tested ratios for the flexural strengths of the strengthened beams using ACI 440.2R-17, CNR-DT 200 R1/2014 (based on PE debonding failure), CNR-DT 200 R1/2014 (based on IC debonding failure), and GB 50608-2020 are 0.994, 0.704, 0.946, and 0.930, respectively.