Molecular Dynamics Simulation Of Mechanical And Frictional Properties Of Oriented Carbon Nanotubes/Polycarbonate Composites

When polycarbonate(PC)is used in gear,worm gear,shaft sleeve and other wearresistant parts,it often needs wear-resistant treatment.As a kind of nano material with high aspect ratio and high specific surface area,carbon nanotubes(CNTs)show excellent mechanical properties in axial direction,and they are often used as nano reinforcing fillers to blend with other matrix materials,which can effectively improve many properties of matrix materials.It is difficult to explore the mechanical and friction properties of aligned carbon nanotubes / polycarbonate composites by molecular dynamics simulation,and to explain the mechanism from the microscopic point of view.In order to explore the effect of the orientation of carbon nanotubes in PC matrix on the mechanical and friction properties of PC matrix and its micro mechanism,three system models were constructed based on molecular dynamics method.First,the tensile model: the pure PC system and the oriented single wall carbon nanotube(SWNT)/PC composite system were stretched in different directions.Second,carbon nanotubes pull-out model: carbon nanotubes with different diameters and lengths are pulled out from PC matrix.Third,friction model: the friction model is a three-layer structure constructed in Cartesian coordinate system,the top layer is used for sliding friction,the middle layer is used for the friction system,and the bottom layer is used for adsorption and fixation of the friction system.The friction system includes PC matrix,X-SWNT/PC composites,Y-SWNT/PC composites and Z-SWNT/PC composites.At the end of the simulation,the data of the interaction between PC molecular chain and carbon nanotubes,the change of potential energy and the migration behavior of PC molecular chain were extracted from the system.The results show that the PC molecular chain can transfer the stress to the carbon nanotubes under the external force,thus enhancing the mechanical properties of the matrix.Therefore,the mechanical and friction properties of oriented SWNT/PC composites are improved compared with pure PC matrix,and the degree of improvement depends on the ability of different oriented carbon nanotubes to transfer stress.At the same time,the interfacial bonding strength between CNTs and PC has nothing to do with the length of CNTs,but increases with the diameter of CNTs.Friction simulation is different from mechanical tensile simulation.The more serious the interface failure occurs,the worse the friction performance of the system.The degree of failure is related to the orientation of carbon nanotubes.At the same time,the interface interaction between CNTs and PC matrix is mainly van der Waals(VDW)interaction.