The circular economy (CE) shifts from a linear economy (LE) to prioritize preserving value improving resource efficiency through closed loops. This shift demands product designs that facilitate repurposing and recycling, reducing waste and new material use. Achieving this requires changes in industry practices, consumer behavior, and supportive policies/incentives. Yet, the absence of standardized metrics poses evaluation challenges. This study introduces a combined life cycle and techno-economic assessment within a parametric design model to optimize CE strategies, including a disassembly planning algorithm linking end of life (EoL) outcomes (reuse, remanufacturing, recycling, landfill) to the life cycle inventories. Applied to a permanent magnet synchronous motor in an electric vehicle, the model evaluates supply risk, environmental benefits, and economic gains compared to LE methods. A one-way sensitivity analysis on motor collection rates explored three scenarios: baseline, 100% disassembly and recycling, and 100% reuse. Results showed significant improvements in economic and supply risks aspects under CE though environmental impact was less pronounced due to the high energy use during the use stage. Furthermore, EoL motor upper-level subassemblies had a greater effect than lower-level ones, with no interaction effects found. This paper proposes a formal method for measuring CE performance based on these findings.