Mechanical properties of fiber-reinforced polymer bars under various types of stress-strain state

The object of research is fiber-reinforced polymer bars of a periodic profile with diameters of 4 mm, 6 mm, 8 mm, 10 mm, and 12 mm, manufactured by pultrusion-pulling glass fiber impregnated with a liquid epoxy resin-based binder through a round die. This work aims to study the physical and mechanical characteristics of fiberglass rods used for reinforcement concrete structures. Method. Experimental studies are conducted to determine the physical and mechanical characteristics of glass fiber-reinforced polymer rebar and compare the mechanical characteristics of glass fiber-reinforced polymer bars with steel bars of classes A-III and A-IV. Results. The experimentally established physical and mechanical characteristics of fiberglass reinforcement show the following values: tensile strength is 1080-1338 MPa, compressive strength is 405-520 MPa, transverse shear strength is 218-250 MPa, bond strength with concrete is 12.6-15.9 MPa, elastic modulus is 50.7-54.2 GPa. After keeping the specimens in an alkaline environment, the bond strength of the bars to concrete decreased by 5-21% for rod diameters of 4 mm, 6 mm, and 12 mm, and tensile strength decreased by 6-10% for rod diameters from 4 mm to 10 mm. The maximum operating temperature for glass fiber-reinforced polymer rebar is 92 °C - 101 °C, depending on the diameter. In terms of its mechanical characteristics, glass fiber-reinforced polymer rebar is superior to steel reinforcement in all respects, except for the modulus of elasticity, which is almost four times lower than that of steel rebar. The average value of the tensile strength of glass fiber reinforced polymer rebar is 65% higher than that of steel rebar, the tensile strength is 23% higher, and the bond strength with concrete is 80% higher.