Durability Test And Simulation Study Of CFRP/Steel Composite Structure

Carbon Fiber Reinforced Polymer(CFRP)has excellent corrosion and fatigue resistance,high specific stiffness and specific strength,easy processing and forming,and convenient construction.The reinforcement technology for externally bonded CFRP sheets is gradually mature and has been widely used to strengthen the steel structure.The peeling failure of the steel/adhesive layer interface is a common failure form of CFRP/steel composite structures.The interface bonding strength has become an important factor affecting the overall mechanical properties of the composite structure.It is urgent to improve the interface bonding strength.Shot blasting surface treatment technology is used to increase the surface roughness of the steel plate.Based on the short fiber reinforcement mechanism,an insulating,high-strength and tough aramid fiber is introduced into the bonding layer to pre-wet the surface of the adherend,and the composite structure is single-lapped.Corrosion or fatigue tests were carried out,and the anti-corrosion and anti-fatigue properties were studied through static load shear tensile test.The constitutive model of the bonding layer of each test type was obtained through the test,and the microscopic observation was carried out.Finally,the finite element model was established.The rationality of the reinforced structure is verified by simulation analysis.The main research contents include:(1)Complete the constitutive model test of CFRP/steel composite structure.Based on the short fiber reinforcement mechanism,an ultra-thin aramid short fiber film is produced.In order to improve the bonding interface strength,the surface shot blasting technology is used to roughen the surface of the steel plate,and the insulation,high strength and toughness of the aramid fiber is "embedded".”Strengthen the bonding layer between CFRP and steel,and prepare single lap joint specimens,design a constitutive model test tool and galvanic corrosion device,and test five types of composite structures(no fatigue,no corrosion,Galvanic corrosion 24 h,galvanic corrosion 72 h,fatigue loading 24 h and fatigue loading 72h)constitutive model of the bonding layer,the static load shear tensile test results show that the specimens containing the aramid fiber bonding layer have a higher limit The main failure mode is the cohesive failure of the adhesive layer.Microscopic observations show that the aramid fibers that penetrate the adhesive layer are pulled out and fractured.The steel/adhesive layer interface and the CFRP/adhesive layer interface are sticky.Well connected;(2)Study the anti-corrosion and anti-fatigue properties of the adhesive layer containing aramid fibers to verify the rationality and effectiveness of the adhesive layer.Under five test conditions: no fatigue and no corrosion,24 h galvanic corrosion,72 h galvanic corrosion,24 h fatigue loading and 72 h fatigue loading,the ultimate load-bearing capacity of specimens containing aramid fiber compared to specimens without aramid fiber The strength has increased by 14.8%,21.3%,19.6%,16.8% and 27.7% in turn,indicating that the highstrength aramid fiber penetrating the adhesive layer can increase the ultimate bearing capacity of the CFRP/steel composite structure during the cohesive failure stage of the adhesive layer;The bonding stiffness increased by 38.4%,27.0%,96.7%,72.5% and 56.9%in turn,indicating that the bonding layer containing aramid fiber has good resistance to deformation;the fracture energy increased by 84.9%,31.1%,17.0 %,18.9% and 30.3% in turn,indicating that the ductile aramid fiber can significantly increase the fracture energy of the composite structure,even after galvanic corrosion or fatigue loading,the composite structure maintains good fracture resistance;(3)Based on the constitutive model of the bonding layer,the three-point bending test of the CFRP reinforced notched steel beam was simulated and analyzed,and the effectiveness of the reinforced structure was verified.Based on the key parameters of the constitutive model obtained from the experimental test,using the ABAQUS finite element software,the three-point bending test of the CFRP reinforced notched steel beam with different bonding layers was simulated,and the shear stress and the bonding layer in the degradation process were analyzed.Normal stress and simulation results verify the effectiveness of the reinforced structure,and provide a reference for the engineering application of CFRP to strengthen damaged steel beams.