| Carbon fiber reinforced polymer(CFRP)is bonded to the fatigue crack of steel structure by epoxy adhesive for reinforcement and repair.It is becoming an attractive reinforcement method because of its advantages of zero damage to the original structure,simple construction and good fatigue resistance.The bonding interface layer between CFRP and steel components is the weak part of the reinforcement structure,and the performance of the adhesive has a significant impact on the bonding performance of CFRP/steel.Temperature and humidity are the most important environmental factors affecting the durability of bonded structures.In this paper,in order to improve the mechanical and heat resistance of epoxy adhesives,the modification of epoxy adhesives was studied by using high-performance nanomaterials,and the experimental study on the influence of hygrothermal coupling aging on the properties of nanomaterials adhesive and CFRP/steel bonding structure was carried out.The main research contents and results are as follows:The epoxy adhesive modified by carboxylated carbon nanotubes with different content was prepared by ultrasonic dispersion and dispersant.Quasi-static tensile shear test,dynamic mechanical test and heat deformation test at different temperatures were carried out for epoxy adhesives.Based on the static and dynamic mechanical response,glass transition temperature and heat deflection temperature at different temperatures with the change of dosage,the optimal dosage and mechanism of carboxylated carbon nanotubes in epoxy adhesives were obtained and analyzed.The optimal dosage and action mechanism of carboxylated carbon nanotubes in epoxy adhesives were obtained and analyzed.When the doping amount was 0.5 wt%,the tensile strength and shear strength reached 52.8MPa and 15.1 MPa at 20℃,and the glass transition temperature Tg,s and heat deflection temperature(A method)were 79.2℃ and 70.8℃,respectively.Accelerated aging tests were carried out on CFRP/steel bonded joints with nanomaterial adhesive at different immersion temperatures.The water absorption and diffusion behavior of the adhesive at different water bath temperatures,the static and dynamic mechanical properties after immersion,and the interfacial bonding properties of the CFRP/steel bonded joints after immersion were tested.The results were compared with those of the specimens without immersion.The influence of the temperature and time of hydrothermal aging on the above properties was revealed.Based on ABAQUS software quality analysis module,the moisture absorption and diffusion behavior of adhesive colloid was simulated,and the simulation results were in good agreement with the experimental results.Based on the ABAQUS subroutine USDFLD field variable updating method,the wet diffusion force sequential coupling finite element analysis of CFRP/steel bonded joint was carried out.The moisture concentration distribution of adhesive layer in CFRP/steel bonded joint was predicted,and it was confirmed that the water bath immersion mainly caused the degradation of CFRP/adhesive layer interface and steel/adhesive layer interface strength. |
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