| Increasing the level of informationization of civil engineering in the current social background is of great significance to the development of civil engineering.Informationization of civil engineering incudes both the informationization of technology and the informationization of management,and a very important part of which is structural health monitoring.Epoxy resin has a lot of advantage including low cost,small curing shrinkage,easy processing and modeling,short curing age,excellent mechanical performance,good corrosion resistance and good heat resistance.In addition,the properties of epoxy resin can be easily modified by using different modifier and curing methods.So it has great advantages to manufacture smart material using epoxy resin.For the composite,the main research is as follows:(1)Choice of material.By comparing the viscosity-temperature curve,it is concluded that E51 is more suitable as the matrix material than E44.In consideration of dispersibility,DMF is chosen as the solvent of epoxy resin and L-MWNT-2040 is chosen as conductive phase by ultraviolet-visible spectrophotometry analysis.(2)Dispersion processing.The optimal ultrasonic parameters were obtained by testing the dispersion effect under different ultrasonic power,ultrasonic time,ultrasonic mode and mixed solution dosage.The ultrasonic power was 60%and the ultrasonic mode was 3s/3s,ultrasonic time is 30min,the amount of epoxy resin is 150g.Furthermore,the influence of temperature and solvent dosage on the dispersion effect was analyzed.The results showed that the higher the temperature of the mixture was,the worse the dispersing effect was,and the dispersion effect of MWCNTs was more favorable when the dosage of DMF was 10%.The influence of temperature and storing time on the stability of the dispersed solution was analyzed based on the dispersion effect of solution,and the higher the storing temperature was the worse the stability of the solution was;the higher the temperature was the better the stability of the solution was.(3)Curing processing.The effects of hardener dosage,normal-temperature curing and high-temperature curing time on the microhardness of cured composite were analyzed.The optimal amount of DETA was obtained(9%of EP).The favorable curing process was determined at last,that is,curing at normal temperature for 9 h and at high temperature for 2 h.(4)Mechanical properties.The destruction process of composite under pressure was analyzed,and the result showed that the elastic limit of composite is about 45MPa,and the elastic modulus is about 1GPa to 2GPa.The delayed elasticity of composite was also studied,and it is concluded that the higher the load is,the more significant the delayed elasticity is.(5)Smart performance of composite.The percolation threshold of composite was obtained(about 0.5 to 0.8wt%)by testing the resistivity of composite contain different dosage of MWCNTs.The change of the resistivity of the composites with different MWCNTs concentration under cyclic load was test,and the conclusion showed that the lower the concentration of MWCNTs,the better the sensitivity was.The noise in resistance change rate-time curve is related to the concentration of MWCNTs,and the lower the concentration is the more the noise is.By analyzing the change of the resistivity of the composite under the temperature cycle,it is concluded that the resistivity of the composite increases or decreases with the increase or decrease of the temperature.With the temperature cycling,the resistivity of the composite will gradually reduce.In addition,the influence of moisture on the resistivity was tested in this paper.The results show that the influence of moisture on the resistivity of the composites is negligible. |
PDF Full Text Request