| Carbon fiber reinforced composites have been widely used to reinforce steel structures for their light weight,high strength,easy molding,good corrosion resistance and fatigue resistance,and convenient construction.However,the adhesive layer is the weak point of the carbon fiber/steel composite structure.Many researches focus on that how to improve the bonding layer strength.In this paper,steel surface was roughened by grooving and sandblasting.The short aramid fiber film was prepared to enhance fracture toughness of the carbon fiber steel composite structural adhesive layer based on the short fiber bridging reinforcement mechanism.The failure mechanism of each bonding layer structure was studied by tensile test under the design of the static shear tensile test fixture.The bond-slip constitutive model of bonding interface was obtained by testing.The rationality of the constitutive model was checked by finite element analysis and experimental comparison.The main research contents are as follows:(1)The steel surface of carbon fiber reinforced composite structure was roughened by grooved surface technology.The short aramid fiber film may be effectively embedded in epoxy adhesive matrix of the carbon fiber fabrics oriented at 0°and 90°to get a strong pulling resistance.Carbon fiber/grooved steel composite structure was prepared by pressure curing.It is shown that the structure between the interface layer and bonding layer have been enhanced by the bridging effect of aramid staple fibers on the surface of grooved steel and carbon fibers.The average load is 5.8 kN and the fracture toughness is 1.85 N/mm.The constitutive model of the bonding layer structure is obtained by testing.(2)The short aramid fiber cannot be embedded in the bottom of the grooves in term of carbon fiber/grooved steel composite structure reinforced by the aramid fiber film.Therefore,the carbon nanotube pretreatment solution was used to pretreat the steel surface.And carbon fiber/grooved steel composite structure was reinforced by self-made aramid fiber/carbon nanotube hybrid structure.The results show that the bonding failure mode is mainly interface failure by the static load shear tensile test.In addition,the delamination failure of carbon fiber sheets in some specimens indicated that carbon nanotubes can further improve the bonding strength.The average load value and the fracture energy of these specimens are 8.43 kN and2.37 N/mm,respectively.Moreover,the constitutive model of the bond layer structure is obtained by the testing.(3)Carbon fiber/sandblasted steel composite structure reinforced by Carbon nanotube was prepared by roughening steel surface with surface sandblasting technology and pretreating steel surface with carbon nanotube pretreatment solution.The results show that the failure mode of bonding interface is mainly the failure of bonding layer by the static load shear tensile test.The average load value and the fracture energy of these specimens are 3.49 kN and 0.338 N/mm,respectively.Furthermore,the constitutive model of the bond layer structure is obtained by the testing.(4)The ENF test of carbon fiber/steel composite structures with three different bonding layer structures was simulated by ABAQUS finite element software based on the three constitutive models of bonding layer structures.It is shown that the simulation results of the load-displacement curves are consistent with the test results.So the rationality of the simulation model was verified.And the stress distribution in the failure process of the bonding layer was studied based on the finite element simulation analysis. |
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