Development And Study On The Behavior Of Hybrid Composite Rebars Used For Concrete Structure

Fiber reinforced composite (FRP) is a new kind of construction material which possesses advantages of high strength, light weight, corrosion resistance, no-magnetism, easy to construct and etc. To choose FRP as reinforcement of concrete structure to replace steel rebar has been the recent research topic. Now the application of this kind of new material in USA, Japan and Europe has been very mature. This kind of reinforcement has a very bright future.Through experimental research of fabrication process and property of FRP rebar, the intermixing effect, fracture mechanism and theoretical analysis method of hybrid FRP rebar have been discussed in this paper. The tensile strength of unidirectional hybrid FRP rebar has been studied. The two-scale 3D model for tensile behavior of unidirectional hybrid composites was developed and the experimental data tallied with the result based on this model when applied on the calculation of strength of peel-core and dispersed FRP rebar. The parameters analysis and experimental comparison of different volume faction and hybrid method of carbon fiber and glass fiber were carried out, the results showed that when the volume fraction of carbon fiber was 5%, the materials showed 2-time fracture characteristic, while one time when the volume fraction of carbon fiber was higher than 5%. There is little effect of hybrid method on the strength and elongation at break of hybrid FRP rebar, the built model reflected the tensile strength and fracture characteristic.The combination of pultrusion process and winding process may be used to fabricate hybrid rebar for civil engineering. The winding device, heating and curing device, resin prescription system, technical system were developed based on pultrusion process in this thesis. The parameters analysis implied that the properties of final products had something to do with the resin prescription system, processing temperature, speed and technology. The built technological and prescription system may be used to fabricate hybrid rebar. The tensile fracture process and characteristic of hybrid rebar were analyzed through the tensile experimental results of two kinds of hybrid structures, 18 groups of different hybrid ratio. The experimental results basically met with theoretical prediction, the tensile modulus accorded with mixing rule and there are two kinds of fracture styles in this hybrid rebar. Through suitable compounding of carbon fiber and glass fiber, the tensile strength, modulus and elongation at break of FRP rebar with one type of fiber may be improved. The modified testing method for tensile strength was developed according to experimental results which may be used to principal design of hybrid rebar.The fatigue and binding properties of hybrid rebar were studied; the effect of fiber type on the properties of hybrid rebar was approached. The results indicated that the fatigue property of FRP rebar reinforced by high strength glass fiber was distinctly higher than that by E-glass fiber. The fatigue property of FRP rebar reinforced by No 4 high strength glass fiber was distinctly higher than that by No 2 high strength glass fiber. The high frequency method may be used testing of fatigue properties of FRP rebar. The adhesive strength between FRP rebar and concrete is a little lower than that between steel rebar and concrete.The application experiments of FRP rebar were made by sewage disposal pool based on the design of material property and structure. The results implied that the experimental value of crack and deformation of concrete was less than that of theoretical prediction, and the concrete structure was in normal working state.