In-house processing of carbon fiber-reinforced polyetheretherketone (CFR-PEEK) 3D printable filaments and fused filament fabrication-3D printing of CFR-PEEK parts

Poly-ether-ether-ketone (PEEK) has several approving mechanical properties; 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 durations and speeds on the extent of uniform dispersion of the CFs in the PEEK matrix. Next, we fed the CFR-PEEK milled powders into a high-temperature extrusion setup to develop uniform-diameter CFR-PEEK filaments. We analyzed the effects of different extrusion parameters on the uniform-diameter CFR-PEEK filament quality to make it suitable 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 4 h were apt for developing uniform CFR-PEEK mixtures. Interestingly, increasing the CF content above 10 vol% resulted in brittle filaments. The extrusion temperature, speed, and cooling rate played a major role in forming the uniform-diameter CFR-PEEK filaments. Finally, the 3D-printed CFR-PEEK parts exhibited a tensile strength of 49 MPa, lesser than unfilled PEEK. We indicate that poor interfacial bonding of the CF with the PEEK matrix is a primary reason for this reduced strength. In addition, printing defects such as pores also contributed to the reduced strength of the CFR-PEEK parts.