This research explores the use of carbon/epoxy and fiberglass/epoxy fiber-reinforced polymer (FRP) composite rebar manufactured on a three-dimensional braiding machine for use as reinforcement in concrete beams under four-point bending loads. Multiple tows of prepreg composite fibers were pulled to form a unidirectional core. The core was consolidated with spirally wound Kevlar fibers which were designed to also act as ribs to increase pullout strength. The rebar was cured at 121â—¦C (250â—¦F) in an inline oven while keeping tension on the fibers. Five configurations of reinforcing bars were used in this study as reinforcement in concrete beam specimens: carbon/epoxy rebar and fiberglass/epoxy rebar were manufactured on the three-dimensional braiding machine and cured in an inline oven while still under tension immediately after production; carbon/epoxy rebar was manufactured by IsoTruss industries on the three-dimensional braiding machine and was rolled and stored before curing; fiberglass/epoxy rebar was purchased from American Fiberglass; conventional No. 4 steel rebar was also purchased. All bars were embedded in 152 cm (60 in) long, 11 cm (4.5 in) wide, and 15 cm (6.0 in) tall concrete beams. Beams were tested under four-point bending loads after which three 30 cm (12 in) specimens were taken from the ends of each configuration to be tested under axial compression loads in order to investigate the effects of the concrete voids on the concrete strength. Concrete beams reinforced with BYU glass/epoxy rebar manufactured on the three-dimensional braiding machine exhibited 5% greater compression bending stress and 11% greater tension bending stress than concrete beams reinforced with industry manufactured glass/epoxy rebar. Concrete beams reinforced with BYU carbon/epoxy rebar manufactured on the three-dimensional braiding machine exhibited 18% lower compression bending stress and 64% lower tension bending stress than concrete beams reinforced with industry manufactured carbon/epoxy rebar. BYU glass/epoxy rebar has a 3% greater stiffness and 1% greater displacement than industry manufactured glass/epoxy rebar and BYU carbon/epoxy rebar has a 40% greater bending stiffness and 19% lower displacement than industry carbon/epoxy rebar. BYU carbon/epoxy rebar has 49% lower compression bending stress, 1% lower tension bending stress, 28% lower displacement, and a 68% greater bending stiffness than BYU glass/epoxy rebar. BYU glass/epoxy rebar has 38% greater compression bending stress, 30% lower tension bending stress, 26% greater center displacement, and a 105% lower bending stiffness than conventional steel. BYU carbon/epoxy rebar has 8% lower compression bending stress, 31% lower tension bending stress, and 22% lower bending stiffness than steel. The deflections of steel reinforced concrete and BYU carbon/epoxy reinforced concrete are comparable with steel rebar displaying a 1% greater center displacement than BYU carbon/epoxy rebar.
College and Department
Ira A. Fulton College of Engineering and Technology
BYU ScholarsArchive Citation
Rice, Kolten Dewayne, "Bending Behavior of Concrete Beams with Fiber/Epoxy Composite Rebar" (2019). Theses and Dissertations. 9062.
composite, carbon/epoxy, fiberglass/epoxy, rebar, FRP, reinforced concrete