Study On Interfacial Bonding Performance Between CFRP Plate And Steel Plate Under Static Load

Carbon fibre reinforced polymer(CFRP)has excellent mechanical properties,such as high Young’s modulus,high tensile strength,good corrosion resistance and fatigue resistance,which can be used to reinforce and repair steel structures.The technology of strengthening and repairing steel structure with CFRP is to use adhesive to stick CFRP on the surface of steel structure according to the strengthening standard,so that part of the force borne by steel structure is transferred to CFRP through the bonding interface,thus achieving the compound effect and working together,giving full play to the material properties of CFRP,thus improving the mechanical properties of the structure and prolonging the service life of the structure.Because the bonding interface between CFRP and steel is the weakest part of the whole strengthening system,the failure of the bonding interface will greatly reduce the strengthening effect and even lead to the failure of the structure.Therefore,the key to improve the strengthening effect of CFRP-to-steel structure is whether the bonding performance of CFRPsteel interface can meet the load-bearing requirements.Therefore,aiming at the bonding interface,which is the most vulnerable part in the steel structure strengthened with CFRP,this paper takes the CFRP-steel plate double shear specimens as the research object,and analyzes the bonding performance of CFRP-steel plate interface under static load by combining theoretical analysis,experimental research and numerical simulation,and obtains various parameters that can determine the bond performance.The main research contents and related conclusions of this paper are as follows:(1)The bonding performance of CFRP-steel plate interface was studied theoretically.The mechanical model of CFRP-steel plate double shear specimen is established.The shear stress formula of CFRP-steel plate interface and the ultimate bearing capacity formula of specimen are derived by linear elasticity theory.The bonding performance of CFRP-steel interface is analyzed and discussed from two angles of interface shear stress distribution and interface maximum shear stress respectively.The results show that the tensile stiffness of steel plate and CFRP will influence the experimental study on the relationship between the maximum shear stress and the thickness of adhesive layer.When the two values are large enough,the relationship between the maximum shear stress and the thickness of adhesive layer is the most universal.(2)Double shear tests were carried out on CFRP-steel plate specimens.Axial tensile load was applied to CFRP-Q345 B steel plate specimens and CFRP-X100 steel plate specimens by universal testing machine.The ultimate bearing capacity,effective bonding length and average bonding strength of CFRP-steel interface were measured by DIC measuring system and strain gauges,and the failure mode of specimens was determined.The influence of adhesive layer’s thickness and steel plate’s material on interfacial bond-slip constitutive model and interfacial shear performance was analyzed and discussed.The results show that the ultimate bearing capacity of CFRP-steel plate specimens with adhesive layer’s thickness of 0.1mm is completely determined by the shear capacity of the interface between steel plate and adhesive layer,and the failure mode of these specimens is the failure of the interface between steel plate and adhesive layer,and their damage-failure processes is relatively rapid;The ultimate bearing capacity of CFRP-steel plate specimens with adhesive layer’s thickness of 0.5mm is determined by the shear capacity of adhesive layer,and the failure mode of specimens is cohesive failure of adhesive layer,and their damage-failure processes is relatively slow;The bond-slip relationship of CFRP-steel interface can be expressed by bilinear constitutive model.(3)The bonding performance of CFRP-steel plate interface was numerically simulated.The cohesive element in ABAQUS is used to model the interface between CFRP and steel plate.By inputting the constitutive parameters,a cohesive model which can simulate the interfacial bonding performance is established,and the change of stress state of CFRP-steel plate specimens during loading is simulated.The damage process and failure mode of CFRP-steel plate interface are analyzed and discussed in detail.The results show that the bonding performance of CFRP-steel plate interface can be well simulated by cohesive element in numerical model,especially when the failure mode of specimens is cohesive failure of adhesive layer,the ultimate bearing capacity can be calculated very accurately by numerical simulation.