| Carbon Fiber Reinforced Polymer(CFRP)has become a hot spot in civil engineering research and application due to its light weight,high strength,and corrosion resistance.Fiber Reinforced Polymer(FRP)grid due to its unique material characteristics has technical advantages,such as convenient construction and good integrity,and it is gradually used in engineering.When FRP materials are actually applied in coastal projects,they will inevitably be affected by a variety of environmental factors at the same time.This environmental coupling will cause accelerated deterioration of the appearance and mechanical properties of the material.Thus,it will affect the durability of the structure.Therefore,studying the mechanism and degradation laws of CFRP grid performance degradation under seawater and stress environments is of great significance for the practical engineering application of CFRP grids.The paper adopts the method of combining experiment and theory,the main research contents and conclusions are as follows:(1)Summarizing the aging phenomenon and damage mechanism of common resin,fiber and interface in the application of FRP materials.According to the aging law of materials under environmental erosion to present the durability model of FRP three-stage(platform period,fast drop period,slow drop period).This model has high fitting degree to test data.(2)Durability tests of CFRP grids with periods of 0,30,60,120,180,270 and 360 days were carried out under the action of aqueous solution,dry-wet cycle of seawater,seawater and stress coupling.110 destructive and 15 non-destructive test specimens were designed under the conditions of aqueous solution,seawater and the dry-wet cycle of seawater,there are 70 specimens about stress coupling of seawater with 30%f_uand 60%f_u(ultimate tensile strength),plus 0 time control group,there are 200 specimens in total.By tensile test to study the degradation law of mechanical properties,and microanalysis of material erosion of the surface resin,cross-section resin-fiber interface of longitudinal section were studied by SEM electron microscope.The results show that the CFRP grid has better durability in aqueous solution,seawater solution and seawater dry-wet cycle environment.The elastic modulus decreased by 3.1%,3.2%and 3.9%respectively after 360 days of aging,,and the tensile strength decreased by 6.2%,10.2%and 10.9%respectively under the same condition.Under the coupling of seawater and stress with 360 days,the elastic modulus of the CFRP grid decreased by 3.6%,5.0%and 7.1%.Besides,the tensile strength decreased by 10.2%,12.3%and 20.2%,and the elongation decreased by 6.8%,7.7%and 14.1%.CFRP grid deterioration is accelerated with the increase of stress level,and the SEM results are consistent with the mechanical properties results.(3)The interaction between environment was analyzed under different working conditions,and the acceleration effect of stress level on environmental erosion was established by fitting durability test data.The acceleration factor of environmental erosion coefficient with the change of stress(pull)level is obtained.For the prediction of FRP durability in stress-coupled environment,compared with the experimental data,it is found that the prediction of material durability through stress acceleration factor is more accurate under the premise that the material has similar damage mechanism in the environment.However,there is a great volatility of durability prediction with different aging damage mechanism. |
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