Microstructural Evolution Investigation on the Effect of Fluorinated Graphene Content on the Mechanical and Tribological Properties of Polyimide Composites Based on Molecular Dynamics Simulations

ABSTRACT To investigate the influence of fluorinated graphene (FG) contents on the microstructure, mechanical, and tribological properties of polyimide (PI) composites and their underlying mechanisms, PI/FG composite models with 0 wt%, 1 wt%, 3 wt%, and 5 wt% FG were constructed, simulated, and calculated via the Materials Studio (MS) platform. Results show that uniformly dispersed low‐content FG enhances intermolecular bonding through van der Waals forces and fluorine‐polar imide group interactions, suppressing chain segment thermal motion to compact molecular chain arrangement, reduce free volume fraction (FFV), and increase modulus—for 1 wt% FG, the composite's Young's, shear, and bulk moduli are approximately 77%, 95%, and 39% higher than pure PI, respectively, showing optimal mechanical reinforcement. However, FG agglomerates when its content exceeds 3 wt%, and interface micro‐voids weaken stress transfer, lowering mechanical properties; tribologically, FG's low surface energy and interfacial enrichment enable migration to form a stable lubricating film during shearing, reducing friction coefficient (CoF), with the 3 wt% FG sample exhibiting the highest interfacial bonding energy, most intact lubricating film, and lowest CoF (≈0.08), revealing a key finding that the “mechanical optimum point” does not overlap with the “friction‐reduction optimum point”. In summary, this study clarifies FG's dual mechanism in PI matrices (“dispersion‐induced reinforcement and agglomeration‐induced deterioration”) and its friction‐reducing mechanism via interfacial migration/enrichment to form a lubricating film.