Multi-Scale Friction Simulation and Experimental Verification of Carbon Nanotube-Reinforced PTFE Composites

Abstract The synergistic analysis of friction properties of carbon nanotube (CNT)-reinforced polymers at the nanoscale and macroscale can help to obtain the intrinsic mechanism of carbon nanotubes to reduce the friction coefficient of polymers, which is important to guide the modification of polymer friction properties. However, the huge gap in spatial scales makes it difficult for molecular dynamics simulations at the nanoscale to predict the friction coefficient of virtual contact interfaces, and conducting a large number of macroscopic experiments to obtain natural frictional laws could be more efficient. This study proposes a multi-scale model to investigate the frictional behavior of copper (Cu)-CNT/polytetrafluoroethylene (PTFE). By using the micromechanics Mori-Tanaka homogenization method as a bridge, the nanoscale simulations of the CNT/PTFE elasticity and frictional behaviour and the macroscopic finite element simulation of the Cu ring-CNT/PTFE block contact are coupled, thus integrating the nanoscale frictional laws of Cu-CNT/PTFE obtained from molecular dynamics simulations into the actual contact interface. The results of multi-scale friction simulations show that the filling of CNTs can effectively improve the elastic and frictional properties of the PTFE matrix, and the degree of improvement is related to the orientation and mass fraction of the CNTs. Under a normal load of 0.5 MPa and a rotating speed of 30 rpm, the friction coefficient continuously decreases (from 0.198 to 0.156) with increasing CNTs mass fraction (0%, 1.25%, 2.5%, 5%). The simulation results were verified by copper ring-CNT/PTFE block friction experiments.