Lightweight Design and Multi-Objective Optimization of E-Glass/Epoxy Composite Leaf Springs for Commercial Vehicles

To address the demand for lightweight commercial vehicle suspensions, this study investigates the replacement of traditional spring steel with E-glass fiber/epoxy composite materials. An equal-width, variable-thickness parabolic single-leaf spring was designed, with orthotropic mechanical properties obtained via ASTM standard tests. Finite element analysis (FEA) was combined with multi-objective optimization using a genetic algorithm, adjusting layup parameters to optimize stiffness, strength, and mass. Furthermore, to address the high failure risk at composite joints, a symmetric two-hole bolted end connection and a mid-span clamping structure were designed. The structural integrity was evaluated under vertical load, emergency braking, and steady-state cornering conditions using the Tsai–Wu tensor strength criterion. The optimization results demonstrate an 8.84% mass reduction for the composite spring main body compared to the initial design. The complete composite leaf spring assembly achieved approximately a 60.6% weight reduction relative to the original steel counterpart. The results indicate that the proposed design and optimization methodology effectively fulfills lightweighting objectives while satisfying all suspension performance and operational reliability requirements.