Effects Of Adhesive Thickness And Temperature Alternation On The Bonding Between CFRP Plate And Steel

Carbon Fiber Reinforced Polymer(CFRP)has attracted wide attention in structural strengthening due to its high tensile strength,good corrosion resistance and light weight,etc.The traditional strengthening methods of steel structures are mainly welding and bolt connection reinforcement,which have some shortcomings,such as damage to existing members,difficulty in construction and difficulty in quality assurance.External bonded CFRP sheets/plates reinforcement of steel structures effectively compensates for the shortcomings of traditional reinforcement methods and has good application prospects.Debonding between CFRP and steel interface is a key problem in CFRP strengthening.The study of short-term mechanical behavior and long-term durability of CFRP-steel interface bonding is the key to solve the problem.Based on this,this paper studies the short-term mechanical behavior of CFRP-steel interface under different adhesive properties and bonding thickness and the long-term performance of interface under temperature alternation.The main contents and conclusions of this dissertation are as follows:Firstly,the effect of adhesive properties(non-linear adhesive Tc and linear adhesive T1)and adhesive thickness(0.5 mm,1 mm,1.5 mm)on the interfacial bonding properties of CFRP-steel was studied by using the CFRP-steel single shear test method.The results show that the properties of adhesives have obvious effects on the ultimate bearing capacity,interfacial stiffness,bond-slip behavior and stress distribution.The interfacial fracture energy and interfacial slip of non-linear adhesives increase with the increase of the adhesive thickness,while the adhesive thickness has little effect on linear adhesives.Secondly,the bond-slip behavior of CFRP-steel interface is studied theoretically,and the key parameters of the bond-slip model of non-linear adhesive under CFRP delamination failure mode are determined.The accuracy of the bond-slip model for predicting the interfacial bond mechanical properties is verified.The influence of bond length and CFRP plate stiffness on the interfacial load-displacement relationship is theoretically analyzed.Finally,the effect of temperature alternation on the interface between CFRP plate and steel was studied.The results show that temperature alternation has little effect on the mechanical properties of CFRP plates,but the elastic modulus of T1 decreases by 9% and the tensile strength of Tc decreases by 17% due to 500 times of temperature alternation.Furthermore,the effect of temperature alternation on the bonding properties of CFRP-steel interface with different adhesives was studied by using the single shear test method of CFRP-steel interface.The interfacial bonding strength of Tc adhesives and the interfacial stiffness of T1 adhesives decrease with the increase of temperature alternation times,but the decrease was less than 10%.Temperature alternation has limited influence on mechanical behavior such as interface failure mode,bond-slip behavior and effective bond length.Based on the existing theory,the distribution law of temperature stress at the interface of CFRP-steel under the action of temperature difference is determined.