Hygrothermal Aging And Molecular Dynamics Simulation Of Carbon Nanotubes/epoxy Resin Composites

Epoxy resin has been applied in various fields,and it inevitably faces hygrothermal environments during use.Under hygrothermal conditions,epoxy resin is prone to aging,resulting in decreased thermal and mechanical properties and shortened service life.Therefore,it is necessary to improve the ability of epoxy resin to resist hygrothermal aging properties.This research takes epoxy resin as the research object,and uses functionalized carbon nanotubes as modified materials to prepare carbon nanotube modified epoxy resin composite materials.Using conducting hygrothermal aging tests and molecular dynamics simulations studied the effect of carbon nanotubes on the hygrothermal properties of epoxy resin.The main achievements are as follows:（1）The effects of MWCNTs-COOH,MWCNTs-OH,and MWCNTs-NH₂on the density,Tg,and mechanical properties of epoxy resins were studied,and the effects of functionalization and content of carbon nanotubes on the properties of MWCNTs/EP composites were explored.The results indicate that the influence of carbon nanotubes on the properties of MWCNTs/EP composites mainly depends on the dispersion of carbon nanotubes in MWCNTs/EP composites and the interaction between carbon nanotubes and epoxy resin.In this study,when the addition amount of carbon nanotubes is 0.4 wt%,the dispersion and performance of carbon nanotubes in MWCNTs/EP composite materials are the best,and the modification effect on epoxy resin is the best.（2）The effects of environmental temperature,functionalization and content of carbon nanotubes on the hygroscopic behavior,Tg,and mechanical properties of MWCNTs/EP composite materials during hygrothermal aging were studied,and the influence of functionalization and addition of carbon nanotubes on the hygrothermal properties of MWCNTs/EP composite materials were explored.The results indicate that the hygrothermal environment can cause damage to the epoxy resin,resulting in a decrease in material properties after aging.Adding carbon nanotubes to the epoxy resin significantly reduces the retention rate of composite materials after hygrothermal aging.In this study,the MWCNTs-NH₂/EP composite material had the highest retention rate of performance after hygrothermal aging,and MWCNTs-NH₂ had the best effect on improving the hygrothermal aging performance of epoxy resin.（3）By using molecular dynamics simulation,a molecular model of carbon nanotubes/epoxy resin was established to simulate the hygrothermal aging behavior of MWCNTs/EP composite materials,and to study the mechanism of action of carbon nanotubes on the hygrothermal properties of epoxy resin.The molecular models of MWCNTs/EP composite materials with different functionalized carbon nanotubes and water absorption rates were established,and the density,energy,free volume,and mean square displacement of water molecules in the models were calculated.The research results indicate that enhancing the interaction between carbon nanotubes/epoxy resin and reducing free volume are beneficial for improving the hygrothermal aging performance of MWCNTs/EP composite materials.