IN-HOUSE PROCESSING OF CARBON FIBER REINFORCED POLYETHERETHERKETONE (CFR-PEEK) 3D PRINTABLE FILAMENTS AND FUSED FILAMENT FABRICATION OF CFR-PEEK PARTS

PEEK is a high-performance polymer known for its exceptional mechanical properties, making it suitable for various applications; however, for certain demanding applications such as automotive, PEEK does not exhibit the required strength. Moreover, if the PEEK parts are developed by Fused Filament Fabrication (FFF)-based 3D Printing, there is a high chance of having PEEK parts with decreased mechanical properties. Carbon Fiber (CF) reinforcement is a well-known method of mitigating the low mechanical properties of PEEK. Hence, in the present study, we attempted to develop CF-reinforced PEEK (CFR-PEEK) parts via FFF. First, we developed homogeneous CFR-PEEK mixtures via ball milling and explored the effects of different milling duration and speeds on the extent of uniform dispersion of the CFs in the PEEK matrix. Once a well-mixed CFR-PEEK powder was achieved, it was processed further by feeding it into a high-temperature extrusion setup. This step focused on producing uniform-diameter CFR-PEEK filaments, which are essential for successful 3D printing. We assessed various extrusion parameters, such as temperature, speed, and cooling rate, to ensure the quality of the filaments met the requirements for 3D printing. Finally, the CFR-PEEK filaments were used in a high-temperature FFF setup to develop design-specific parts. Our results indicate that 400 rpm and 4h were apt for developing uniform CFR-PEEK mixtures. Interestingly, increasing the CF content above 10 vol% resulted in brittle filaments. The extrusion temperature, speed,vand cooling rate played a major role in forming the uniform-diameter CFR-PEEK filaments. However, the 3D printed CFR-PEEK parts exhibited a tensile strength of 49 MPa, which was lower than that of unfilled PEEK. We attributed this reduced strength primarily to poor interfacial bonding between the CF and the PEEK matrix. This suggests that the incorporation of CFs did not yield the expected improvement in mechanical properties due to insufficient adhesion between the reinforcing fibers and the polymer matrix. Additionally, printing defects were identified as a contributing factor to the decreased strength of CFR-PEEK parts, emphasizing the complexity of FFF-based 3D printing for high-performance materials. Overall, this study provides valuable insights into the challenges and considerations involved in developing CF-reinforced PEEK parts using FFF 3D printing technology.