Flexural and Bond Behavior of Concrete Beams Strengthened with Hybrid Carbon-Glass Fiber-Reinforced Polymer Sheets

The combined use of carbon fibers (CF) and glass fibers (GF) was used to strengthen potentially nonductile flexural members. Based on tension tests of fiber-reinforced polymer (FRP) rovings and sheets, as well as theoretical research on hybrid carbon-glass FRP, a volume ratio of (GF/CF) was determined to be approximately (8.8/1) to produce synergistic hybrid effects and pseudo-ductility. The (8.8/1) ratio was used to fabricate hybrid FRP sheets and was verified through four-point loading tests of plain and reinforced concrete (RC) beams strengthened with single or multiple plies of FRP sheets. The increased flexural strengths were evaluated using available design procedures in conjunction with a proposed forcestrain relationship for hybrid carbon-glass FRP sheets. Additionally, six bond tests were conducted to demonstrate that the ultimate bond-shear stress between the hybrid sheet and concrete is similar to the case of the carbon sheet.