| In practical engineering applications,Carbon Fiber Reinforced Polymer(CFRP)Reinforced structures are often subjected to harsh environments,which speeds up the degradation of cfrp-concrete bond interface properties and even results in stripping,shortening the service life of CFRP and causing potential safety hazards.Therefore,it is necessary to study the degradation law of CFRP-concrete bond interface and the corresponding interface damage detection method.In this paper,the interface damage of cfrp-concrete bond was studied by using piezoelectric impedance technology in the context of wet-heat cycling and natural exposure,and it was verified with the existing stripping capacity model and bond slip model.The main research contents and conclusions are as follows:(1)Experimental study on the durability of materials under the action of humid heat cycle and natural exposure environment.The results show that the mechanical properties of CFRP plates change little with time,indicating that CFRP plates have good durability.The tensile strength of epoxy resin decreased obviously under the action of the deteriorating environment,and its tensile strength decreased by 14% and 9% respectively under the humid heat cycle and the natural exposure environment.The elastic modulus and splitting strength of concrete did not change,but the compressive strength of concrete increased slowly due to hydration reaction.(2)The static load test of CFRP-concrete single shear specimens under humid and thermal environment and overload damage.The results show that the failure mode of the specimen under various working conditions is surface concrete stripping failure.Both the damp-heat cycle and overload damage had a negative effect on the ultimate bearing capacity and stiffness of the specimen.The maximum shear stress and fracture energy of the specimen were reduced by degradation of the environment and overload damage.With the increase of fatigue load cycles,the interfacial bonding stiffness and bonding strength of the specimens were reduced due to overload damage,and the residual slippage was also increased.(3)Study on interface performance monitoring method of piezoelectric impedance technology.Static load tests were carried out on the single shear specimens after environmental erosion and overload fatigue.The interface peeling process was monitored by piezoelectric impedance technology,and the interface damage was quantitatively analyzed by impedance curve and RMSD value representing the damage.The RMSD damage value obtained by the piezoelectric impedance technology was compared with the strain value recorded by the strain gauge,and the results showed that the impedance curve could preliminarily identify the damage,and the RMSD damage index could further evaluate the degree of damage.(4)Comparative analysis of experimental data and bond slip model.and verify with the test data.Fit the experimental results based on the Popovics model.The three parameters of the interface regression coefficient n,the peak bonding stress τmax,and the slip amount s0 corresponding to τmax were modified,and the influencing factors of the dry and wet cycle time of the salt solution were considered.Based on the experimental conditions,a bond-slip constitutive model is proposed which takes into account the dry and wet cycling of salt solution. |
