Variation in size of graphite particles and its cascading effect on the performance properties of PAEK composites

Abstract The three composites based on poly (aryl ether ketone) (PAEK) (60 wt %) as a matrix, glass fibers (30 wt %) as a reinforcement and particulate graphite 10 wt % as a solid lubricant were developed with identical composition but differing in the size and hence surface area of graphite particles. The theme of research was to study the influence of size of particles on physical, mechanical and tribological performance of the composites. Graphite particles possess a layer lattice structure which provides efficient lubrication and also enhanced thermal conductivity. The distribution of graphite particles and glass fibers in the bulk of composites was observed using X-ray micro-tomography. All the composites exhibited excellent tribo-performance indicating μ ≈ 0.04, and wear rate ≈10−16 m3/Nm apart from very high PVlimit values (≈112 MPa m/s). Composite containing graphite with smallest particle size (4 μm) performed best, followed by the one with medium size (15 μm). Scanning electron microscopy (SEM), as well as energy dispersive x-ray (EDAX) studies were conducted to observe the transfer film distribution and the wear mechanism. Postmortem analysis on the worn surfaces were performed by Raman spectroscopy. Chemical composition of the lubricating film on the worn disc surface was studied using x-ray photoelectron spectroscopy (XPS).