Tunable Thermal, Mechanical, and Tribological Properties of Polybenzoxazine-Based Composite for Vehicle Applications

In this study, a series of composites comprising polyether ether ketone (PEEK) and carbon fiber (CF)-reinforced polybenzoxazine for high-temperature friction materials for vehicle brake applications were developed using a high-temperature compression molding technique. The objective of this research was to systematically investigate the thermal, mechanical (tensile and flexural), and tribological performance of friction materials made from polybenzoxazine-based composites by varying the PEEK/CF mass ratio. Our study reveals the substantial improvement effect of the increased content of PEEK fibers on the thermal conductivity, the coefficient of friction, and the friction strength of the polybenzoxazine-based composite materials. Meanwhile, the introduction of carbon fibers was found to have a monotonic positive effect on the mechanical (tensile and flexural) properties and wear performance of the polybenzoxazine-based composites. The polybenzoxazine-based composites exhibit high mechanical strength, with a tensile strength of 50.1–78.6 MPa, Young’s modulus of 10.2–24.3 GPa, a flexural strength of 62.1–88.3 MPa, and a flexural modulus of 13.1–27.4 GPa. In addition, the polybenzoxazine-based composite with a PEEK/CF mass ratio of 75:25 exhibits a high and stable coefficient of friction (0.33) and a specific wear rate (1.79 × 10−7 cm3/Nm at room temperature). Subsequent to the wear test at ambient temperature, the worn surfaces of five polybenzoxazine-based composite samples with various PEEK/CF mass ratios were studied using electron microscopy technology (SEM). The observation of small cracks and tiny grooves on the worn surfaces indicates a combined abrasive and adhesive wear mechanism of the material. Our experimental results clearly reveal superior mechanical properties and excellent tribological characteristics. As a result, these composites show promising potential for the application of friction materials in terms of vehicle braking system applications.