This study investigates the crashworthiness of novel non-closed multi-cell tubes (NMCTs) designed using topology optimization. These structures offer an alternative to conventional and bio-inspired designs. Three NMCT groups (I, II, and III) were evaluated under axial and oblique impacts (θ = 0°–30°). The simulation used LS-DYNA with the MAT24 model for AA6061-O aluminum alloy and was validated against experimental results. A mesh convergence study confirmed numerical accuracy. Results show that oblique impacts reduce peak loads, lowering passenger injury risk, while deformation modes transition from progressive folding at θ ≤ 15° to global buckling at higher angles. Certain moderate-thickness configurations (1.2–1.6 mm) sustained progressive folding up to 20°, achieving specific energy absorption (SEA) values of 23.627 kJ/kg at 0° and 21.075 kJ/kg at 10°. Thicker walls (>1.6 mm) were prone to fracture under high oblique angles. Compared with concentric multi-cell, foam-filled, and bio-inspired tubes, the topology-optimized NMCTs delivered up to 87% higher SEA than foam-filled tubes, approximately 74% higher than bio-inspired tubes, and modestly higher (≈6%) than concentric multi-cell tubes at low to moderate oblique angles, while maintaining stable deformation. These findings highlight topology optimization as a systematic pathway for designing lightweight, crashworthy structures capable of efficient energy absorption under multi-directional loading.
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