Study On Tensile Strength Of Glass Fiber Reinforced Polymer Adhesive Joint

Axial tension is a basic form of stress in traditional structures.In metal members,due to fatigue or corrosion,the stiffness of the structure becomes weaker and the bearing capacity decreases.Generally,welding reinforcement technology is used to enhance the metal structure.However,this technology has many shortcomings,such as high maintenance cost,long reinforcement cycle,couple corrosion and so on.Glass fiber reinforced polymers have been widely used in the repair and reinforcement of metal structures because of their excellent mechanical properties,such as fatigue resistance,corrosion resistance,light weight and high strength.In this paper,glass fiber reinforced polymer(GFRP)and 304 stainless steel bonded joint specimens are designed.The tensile strength of GFRP-stainless steel bonded joint is studied according to the influencing factors of joint capacity.Based on the bilinear bond slip constitutive relation,the possible two limit states of GFRP-stainless steel bonded joints under axial load are analyzed,the differential equation between normal stress and slip on GFRP and stainless steel under these two limit states is established.Finally,the tensile strength of adhesive joint are both obtained.The model of GFRP-stainless steel adhesive joint is established by finite element simulation.The bonding model is composed of Inter205 element with zero joint thickness.The bearing capacity and shear stress distribution of the bonded joint with different length of adhesive layer are studied.The tensile strength of adhesive joint is highly consistent with the theoretical solution.The maximum errors of simulation and theory of specimen 1 and specimen 2 are 7.26% and 3.22% respectively,the error is within the allowable range,verifying the feasibility and accuracy of finite element simulation.Comparing numerical simulation,theoretical and experimental results,it is found that the bonding capacity of GFRP-stainless steel bonding joint is not linearly related to the bonding length.In a certain range of bonding length,the bonding ability of the adhesive joint raises with the increase of the length of the adhesive layer.However,under the condition of elastic limit and strength limit,the adhesive joint has effective bonding length.When the bonding length reaches the effective length,the adhesive layer length is increased,and the bonding ability is no longer improved.The results show that the effective bonding length of elastic and limit states is 40 mm and 80 mm,respectively.The influence of temperature on the distribution of shear stress in the adhesive layer and the fatigue life of the joint are studied.In elastic state,the results show that when the temperature of the system is increased from normal temperature to 100?,the average shear stress is reduced by 6.47%.When the temperature of the system is increased to 200?,the average shear stress is reduced by 8.42%,and in strength limit state when the temperature of the system is increased from normal temperature to 100?,the average shear stress is reduced by 1.35%.When the system temperature is increased to 200?,the average shear stress is reduced by 4.61%.Therefore,with the increase of the temperature,the shear stress in the adhesive layer will be reduced,resulting in a decrease in the connection performance of the adhesive joint.The test data shows that the longer the length of the adhesive layer is 30-60 mm,the longer the length of the adhesive layer,the longer the fatigue life of the bonded joint.