EXPERIMENTAL AND THEORETICAL RESEARCH ON FLEXRUAL PERFORMANCE OF RC BEAMS STRENGTHENED WITH HYBRID FIBER SHEETS

An idea of hybrid composites containing carbon fiber, aramid fiber and glass fiber was proposed in this paper. Carbon fiber with high strength and high modulus was used to ensure the enhancement of bearing load, glass fiber with high rupture strains was used to achieve the ductile behavior, and the progressive stress transition in hybrid fiber sheets was realized by the use of aramid fiber. A series of 4-point bending experiments were carried out to investigate the effects of hybrid mode, hybrid structure and layer of fiber sheets on the flexural behavior of beams strengthened with hybrid fiber sheets. Results show that, if the stress in hybrid fiber sheets can’t be transferred stably, the local debonding between hybrid fiber sheets and concrete will occur, resulting in the weakened hybrid effects; with the same total layers of fiber sheets, the cracking load, yielding load, maximum load and ultimate load of RC beams strengthened with carbon/aramid/ glass laminated hybrid fiber sheets are respectively 22%, 12%, 12% and 16% less than that of the RC beam strengthened with single carbon fiber sheets, while the displacement ductility index increases 20%, indicating that the carbon/aramid/glass hybrid fiber sheets can amend significantly the brittleness of single carbon fiber sheets. Based on the experimental research, an elastoplastic section analysis method is conducted to predict the bearing capacity of RC beams strengthened with hybrid fiber sheets, the results from the theoretical predictions and the experiment agree well.