Size-dependent tribological behavior of graphene nanoplatelet-reinforced PTFE composites at cryogenic temperature investigated by reactive molecular dynamics

Reactive molecular dynamics simulations were employed to investigate the impact of graphene nanoplatelets (GNPs) size (designated as G3-G6 in increasing order of edge length) on the tribological performance, interfacial thermal behavior, and microscopic dynamic mechanisms of polytetrafluoroethylene (PTFE)-based composites at 80 K. Results indicate that the largest filler (G6) exhibited optimal lubrication performance, reducing the average coefficient of friction by 36.72%. This improvement stems from the superior load-sharing capacity of G6, which shields the matrix from shear stress concentration and promotes a transition to low-resistance interlayer sliding. Thermal analysis reveals that small-sized fillers (G3 and G4) tend to induce local heat accumulation. Dynamic analysis confirms that the G4 filler exhibited the lowest lubrication contribution due to its obstruction of PTFE molecular chain flow. In contrast, G6 demonstrated a stable cooperative sliding mode, assisting the PTFE molecular chain in achieving low-resistance long-range migration.