Crashworthiness of double-gradient hierarchical multi-cell hexagonal tubes under multi-load impacts

The double-gradient hierarchical multi-cell hexagonal tube (DGHMHT) is introduced, featuring gradient designs in both axial and radial directions of the thin-walled tube. This study investigates the impact resistance of this structure under multi-load conditions using the Abaqus/Explicit finite element model, validated by quasi-static tests. Results indicate that the proposed DGHMHT exhibits superior resistance to overall buckling compared to single-gradient hexagonal laminated thin-walled tubes under multi-load impacts. In addition, it significantly reduces the initial peak force without compromising overall energy absorption, achieving a 74.92% reduction for the double-gradient structure compared to a 72.84% reduction for the single-gradient structure of the same order, respectively. Furthermore, increasing mass substantially enhances the structure’s energy-absorption capacity. Mass increment from 0.0729 to 0.3650 kg boosts Specific Energy Absorption (SEA) nearly tenfold, albeit with a corresponding rise in initial peak force. Examining impact angle effects reveals that the double-gradient structure is less susceptible to overall buckling as the angle increases, with the SEA of DGHMHB-3 surpassing that of hexagonal tube by 34.08% at a 10° impact angle. Analyzing the axial gradient length of DGHMHB-3 suggests that appropriately adjusting layer-height distribution can elevate the structure’s energy absorption and deformation resistance. These findings underscore the effectiveness of the proposed double-gradient hexagonal laminated thin-walled tubes in mitigating collisional impacts, particularly under multi-load conditions.