Aeroelastic response of chiral lattice airfoils: Integrated experimental and finite element assessment of passive morphing

Morphing airfoils enable controlled shape change to improve aerodynamic efficiency across varying flow conditions. This study examines how hexachiral lattice cores influence passive morphing in airfoils, emphasizing the link between structural compliance and aerodynamic performance within the context of multifunctional, architected materials. Two hexachiral lattice configurations (ligament to node ratios L/R = 0.6 and L/R = 0.9) were integrated into a scaled Eppler 420 airfoil; rigid core references were fabricated from PLA and TPU. All specimens were produced by additive manufacturing. Structural response was characterized with finite element point load simulations to quantify localized compliance and deformation trends. Aerodynamic behavior was measured in a closed-circuit wind tunnel using a custom force balance to record lift and drag at zero angle of attack across a range of freestream velocities. Results show that lattice topology alters both mechanical and aerodynamic responses. Point load FEA indicates the lower density L/R = 0.9 lattice is more compliant under concentrated loading, whereas wind tunnel tests reveal greater lift generation for the denser L/R = 0.6 configuration. This divergence underscores the difference between local compliance (point loading) and global flow induced deformation and highlights the importance of relative density normalization when correlating structural metrics with aerodynamic outcomes. The work demonstrates that passive, architected lattice cores can meaningfully modify airfoil aerodynamics at small scales and provides a validated framework for interpreting how lattice geometry governs deformation and lift. These findings establish a baseline for future efforts on density normalized lattice design, geometric scaling, and integration of active morphing strategies for multifunctional adaptive structures.