A Molecular Dynamics Study On Tensile And Tribological Properties Of Ti₃C₂T_X Mxene/Epoxy Resin Composites

Epoxy resins have the characteristics of good mechanical properties,adhesive properties and easy curing,etc.It is a kind of engineering polymer material widely used in aerospace,machining,military equipment and other fields.With the development of industry and the continuous improvement of manufacturing capacity and level,the working conditions and performance requirements of instruments,equipment and mechanical parts are increasingly improved.Due to the brittleness of epoxy resin,its strength will be greatly affected under various working conditions.Therefore,in order to meet the requirements of high performance equipment,high performance parts and high performance processing,the performance of epoxy resin and its composite is required to be higher.In recent years,MXenes,as a new two-dimensional material,has been widely used in polymer matrix composites with its unique mechanical,thermal and electrical properties.As a reinforcing material,it plays a reinforcing role on epoxy resin matrix.At the same time,with the continuous development of computer technology and the gradual maturity of molecular dynamics theory,the method can not only observe the atomic motion trajectory in the system but also calculate the macroscopic properties of the material,which can provide theoretical reference for experimental research.Based on the molecular dynamics theory,the tensile and frictional processes of Epoxy and MXene/Epoxy composites were simulated in this paper,and the microscopic mechanism of MXene enhancing the tensile and frictional properties of Epoxy matrix was revealed.The main research contents are as follows:Firstly,a crosslinked Epoxy model was constructed by using the dynamic crosslinking method to simulate the uniaxial tensile process and microstructure changes of the Epoxy,and the effect of strain rate on the tensile properties of the Epoxy was studied.The results show that with the increase of strain and stress,there are obvious deformation and holes in the system,and the larger the strain is,the more holes there are.The tensile strength increases with the strain rate,but the young's modulus is less affected by the strain rate.At the same time,the friction model between Epoxy and metal iron was constructed,and the friction behavior between the two was simulated,and the influence of load on the friction performance of the Epoxy matrix was studied.The results show that the number of atoms at the Epoxy matrix interface decreases first and then remains basically the same in the sliding process.As the load increases from 60MPa to 300MPa,the friction coefficient first decreases and then tends to be stable.Moreover,the larger the load,the greater the interface interaction energy and the smaller the increment of MSD value,while the epoxy atom in the middle of the friction process is more inclined to move along the Z direction.Secondly,the model of MXene?Ti₃C₂O₂?reinforced matrix and the friction model between the matrix and the metal iron were constructed,and the tensile and frictional properties of the composite were simulated and analyzed.The results show that,due to the van der Waals force and electrostatic action of MXene?Ti₃C₂O₂?,the movement of the epoxy molecular chain tightly adsorbed around MXene?Ti₃C₂O₂?during stretching is restricted,thus improving the tensile strength of the composite.Meanwhile,the friction coefficient,interfacial interaction energy and temperature are effectively reduced,which improves the anti-friction ability of Epoxy.The effect of load on the friction process of Ti₃C₂O₂/Epoxy composite was studied.The variation trend of friction coefficient is the same as that of pure Epoxy matrix.However,as the load increased from 60MPa to 300MPa,the increment of friction force,normal force and interface interaction energy was less than that of the Epoxy matrix.Finally,the difference of mechanical properties of matrix reinforced by different functionalized MXene?Ti₃C₂O₂,Ti₃C₂F₂,Ti₃C₂?OH?₂?was compared and analyzed.The tensile and friction processes of three functionalized MXene reinforcing matrix composites were analyzed.The enhancement mechanism was revealed from the microscopic perspective.The effect of load on the tribological properties of three composites was investigated.The results showed that MXene?Ti₃C₂O₂?had the smallest layer thickness,the smallest space occupied in the matrix,and the maximum interface interaction energy between MXene?Ti₃C₂O₂?and the matrix,thus improving the tensile and tribological properties of the matrix.As the load increases from 60MPa to 300MPa,the interface interaction energy between each MXene and the Epoxy matrix increases,thereby reducing the friction coefficient.