Structural topology optimization provides an effective computational approach for determining optimal material distributions that achieve lightweight and high-performance structures. In this study, the Solid Isotropic Material with Penalization (SIMP) method is employed to investigate and compare single-material and multi-material topology optimization for interconnected automotive structural components. Three material configurations—steel, aluminum, and a steel–aluminum hybrid—are evaluated through numerical simulations. A simplified truck chassis model was used to demonstrate the proposed method. The results show that the proposed multi-material design significantly improves weight reduction and material cost efficiency. The SIMP formulation drives all designs toward a comparable level of material efficiency, with mass reductions exceeding 95% in each case of different materials of the truck chassis model. These findings demonstrate the effectiveness of multi-material topology optimization for developing lightweight automotive structures and provide design insights for next-generation vehicle body systems.
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