Crashworthiness performance of double-walled hull structural filler design using 3D printing SLM technology

• An optimized Double-Walled Hull Structural Filler Design (DWHSFD) based on a Double Arrowhead Auxetic (DAA) structure was developed using AlSi10Mg fabricated by Selective Laser Melting (SLM), considering variations in cell wall thickness ( t ), number of auxetic cells ( n ), and post–heat-treatment conditions ( ht ). • Response Surface Methodology (RSM) revealed that the number of auxetic cell arrangements is the most influential parameter governing specific energy absorption (SEA), followed by cell wall thickness and heat-treatment condition. • The proposed DAA design demonstrates significant potential as an impact-mitigating structural filler for double-walled ship hulls and other marine protective applications. • The stress-relieved DAA structure exhibited early crack initiation and the lowest crashworthiness performance. In contrast, the T6-treated DAA structure showed the highest initial peak crushing force, while the annealed DAA structure provided smoother deformation behavior and more stable energy dissipation. This study presents an optimized Double-Walled Hull Structural Filler Design (DWHSFD) based on a Double Arrowhead Auxetic (DAA) structure manufactured from AlSi10Mg using Selective Laser Melting (SLM). The effects of cell wall thickness (t), number of auxetic cells (n), and post–heat-treatment conditions (ht) were systematically examined. Taguchi analysis was employed to optimize heat-treatment parameters, including temperature, holding time, and aging time, resulting in stress relief at 300°C for 1 h, annealing at 450°C for 2 h, and T6 treatment consisting of solution treatment at 450°C for 1 h followed by water quenching and artificial aging at 150°C for 3 h. Response Surface Methodology revealed that the number of auxetic arrangements is the most influential factor governing specific energy absorption (SEA), followed by wall thickness and heat-treatment condition. The optimal DAA structure was identified as a structure with three arrowhead arrangements and a wall thickness of 1.8 mm. Quasi-static compression tests showed that stress-relieved specimens exhibited early crack initiation and the lowest crashworthiness performance. In contrast, T6-treated structures demonstrated the highest initial peak crushing force, while annealed specimens provided smoother deformation and more stable energy dissipation. Overall, the proposed DAA design demonstrates significant potential as an impact-mitigating filler for double-walled ship hulls and other marine protective applications. Therefore, the optimal heat-treatment condition should be selected according to application-specific requirements to achieve an appropriate balance between strength, ductility, and energy absorption performance.