Tunable stiffness and crashworthiness of selective laser melted AlSi10Mg sinusoidal auxetic structures

This study presents the design, fabrication, and multi-objective optimisation of a novel additively manufactured aluminium sinusoidal ligament auxetic structure (SAS) using AlSi10Mg and Selective Laser Melting (SLM) achieving 99.85% density. Unlike conventional re-entrant designs, the smooth sinusoidal geometry minimises stress concentrations, enhances manufacturability, and provides tunable stiffness and crashworthiness. The SAS lattice, designed with unit cell dimensions of 5 × 5 × 3 mm and global dimensions of 30 × 30 × 20 mm, demonstrated a negative Poisson’s ratio of −0.113 and a compressive elastic modulus of 547 MPa under quasi-static loading (ISO 13314). Finite element analysis (FEA) achieved <3.7% deviation across six key mechanical metrics ranging from E, σ y , − υ , SEA, PCF, and CFE validating numerical predictivity. Response Surface Methodology (RSM) informed by Central Composite Design (CCD) was employed to develop six high-fidelity surrogate models (R² > 0.92, p < 0.0001), capturing the influence of strut thickness (0.2–0.4 mm) and length (0.5–1.4 mm). Parametric optimisation revealed that strut thickness dominantly controlled stiffness, yield strength, and peak crush force, while strut length significantly influenced Poisson’s ratio and crush force efficiency. Three functional optimisation scenarios (S1–S3) yielded tailored structures for stiffness, crashworthiness, and hybrid functionality, achieving maximum SEA of 17.23 kJ/kg and CFE of 73.23%. The results position SAS as a versatile auxetic metamaterial platform with tunable energy absorption for lightweight structural applications.