The Importance of Fiber Orientation for the Performance of High-Performance Polymer-Based Hybrid Materials in Sliding Contact with Steel

The properties of composite materials depend not only on the composition but also on the distribution and orientation of the fillers, i.e., on the internal material architecture. Using the example of two differently composed PEEK-based hybrid materials, the influence of fiber orientation on the tribological behavior of these materials in sliding contact with steel was investigated. The tribological performance of these composites was assessed using a pin-on-disc (PoD) tribometer, testing in a pv range from 0.25 to 32 MPa·m/s. The findings indicate that the printed specimens exhibit a high degree of fiber orientation aligned parallel to the printing paths. Conversely, the injection-molded samples display a three-layered structure across the thickness, with fibers in the skin layers aligned parallel to the injection direction but perpendicular to it in the core. These variations in morphology are evident in both the mechanical properties and the tribological behavior. To describe the influence of the fiber orientation on tribological properties, a model is proposed that allows the prediction of tribological properties for any fiber orientation. Although fiber orientation appears to be the dominant factor in tribological behavior, there is also a clear influence of additional fillers.