Molecular Dynamics Simulation Of The Effect Of Water Intrusion On The Epoxy Resin/Glass Fiber Interface Of Composite Insulator Core

Core rod is an important part of composite insulator,which is mainly composed of glass fiber reinforced epoxy resin composite.In recent years,due to water intrusion and other reasons,mandrel broken string accident is common,which brings serious harm to the safety and stability of power system.The epoxy resin/glass fiber interface is the micro interface in the mandrel,and the bonding strength of the interface has an important influence on the o verall mechanical properties of the mandrel.However,the characterization of degradation characteristics of mandrel is mostly based on mechanical test and physical and chemical morphology analysis,so it is difficult to clarify the degradation mechanism of epoxy resin/glass fiber interface under water intrusion by the above methods.Therefore,based on molecular dynamics method,t he degradation behavior of epoxy resin/glass fiber interface under water invasion was analyzed by molecular simulation technology,and the influence of temperature and electric field on the degradation process was studied.The main work and conclusions of this paper are as follows.The molecular simulation model of epoxy/glass fiber interface in water environment was established.Firstly,the epoxy resin model was built based on the actual composition and proportion.At the same time,the glass fiber molecu lar model was built by surface hydrotreating of silica.Then,the number of water molecules was added according to the saturated moisture absorption.Finally,the epoxy resin/glass fiber interface molecular model under water invasion was built by energy minimization.The simulation temperature was set at 213K?853K.The interfacial structure,interfacial binding energy,the number of ester groups,radial distribution function and the number of hydrogen bonds were studied by molecular simulation method.The influence of water molecules on the epoxy resin/glass fiber interface under the action of temperature was clarified.The results show that when the temperature increases,water molecules are easy to migrate to the interface through the holes in the epoxy resin;When the temperature reaches 373 K,the epoxy resin will undergo hydrolysis reaction under the action of water molecules,wh ich promotes the cracking of epoxy resin;At the same time,the water molecules migrating to the interface can prevent the formation of hydrogen bond between epoxy resin and glass fiber;Under the combined action of the above factors,moisture gradually destroys the epoxy resin/glass fiber interface.The range of electric field strength was set from 1k V/cm to 33 k V/cm.The interfacial structure,interfacial binding energy,number of ester groups,radial distribution function and number of hydrogen bonds were studied by molecular simulation.The influence of water molecules on the interface of epoxy resin/glass fiber was obtained.The results show that the water molecules will move directionally under the action of the electric field strength.If the temperatu re reaches the hydrolysis temperature,the increase of the electric field strength will help the hydrolysis reaction,and further promote the migration of water molecules to the epoxy resin/glass fiber interface.Under the joint action of the hydrolysis of epoxy resin and the reduction of the hydrogen bond between the epoxy resin/glass fiber interface,The interface between epoxy resin and glass fiber was destroyed gradually.At the same time,the influence of water intrusion on the interface of epoxy resin/glass fiber under the synergistic effect of electric field and temperature was studied by changing the electric field intensity and temperature.The results show that at low temperature(213K-293K),the water molecules can move directionally by increasing the electric field value,but the interface between epoxy resin and glass fiber does not change obviously because the hydrolysi s temperature is not reached;As the temperature increases to(373K-613K),the hydrolysis temperature of epoxy resin is reached.Increasing the electric field can accelerate the water migration and the hydrolysis process of epoxy resin.Therefore,increasi ng the temperature and electric field can accelerate the degradation process of epoxy resin/glass fiber interface under water invasion;When the temperature is further increased(613K-853K),the thermal movement of water molecules is intense,and the hydrolysis of epoxy resin is also serious.