Development and Testing of an Ultra-Lightweight Carbon Fiber Rotor for an Aviation Grade 250-kW Axial Flux Motor

This paper presents the design, development, and spin-testing of a carbon fiber reinforced polymer (CFRP) motor-rotor that is currently being used in a high-power-density (power/weight) electric motor for next-generation electric aircraft. The rotor is designed to meet the demanding structural requirements arising from large centrifugal loads (3,800 Gs of loading at the rim) at high rotational speeds of 5,000 RPM, the axial attractive force (5,750 N) between the rotor magnets and stator teeth, as well as the torque, while significantly reducing weight. A quasi-isotropic CFRP laminate was selected to ensure nearly axi-symmetric stiffness and effective load distribution under radial centrifugal forces resulting from the rotating magnets and axial forces from the magnet-stator attraction. Finite element analysis (FEA) was used to evaluate stress distributions and identify critical failure regions using the Tsai-Wu failure criterion. To experimentally verify the design, a spin test was performed at 5,850 RPM, which is 17% above the maximum operating speed, confirming structural integrity. In addition, to further validate the computational model, experiments were conducted to measure the hoop strain at different rotational speeds. The results demonstrated that the computational model predicted the hoop strain of the rotor with an accuracy of 94% at rotation speeds above 2,000 RPM.