Design of a Carbon Fiber Rotor in a Dual Rotor Axial Flux Motor for Electric Aircraft

Due to the interest in electrifying aviation, a study on the electromagnetic and structural design space of a 250 kW dual rotor axial flux electric motor is presented. For commercial viability, the powertrain must have a high specific power, so the entire motor must be as lightweight as possible. The structural design utilizes carbon fiber reinforced polymers (CFRP), which are extensively being used in the aerospace industry for its high-strength, high-stiffness, and low density. The paper presents three separate structural configurations achieving certain relevant performance criteria for the rotor with increasing complexity, and the mass of these CFRP configurations are compared with each other. By taking advantage of the CFRP's anisotropy and appropriately distributing the CFRP mass, the structural mass can be reduced by 59% relative to a solid disk. Then, the pareto frontiers of the carbon fiber designs will be compared with that of aluminum and titanium structural designs to highlight the mass reduction benefits. The optimal CFRP structure has about half the mass of the optimal aluminum or titanium designs. Furthering the study, a co-optimization between electromagnetically active components and sufficient structure support is given. Subsequently, a prototype of the unidirectional spoked disk carbon fiber rotor is fabricated, and static rotor testing is conducted using the designated experimental setup. The observed maximum deflection of the rotor measurements results in a structural compliance of 0.143 mm/kN, which agrees well with the simulations.