Abstract: The insect wing is a rigid-flexible coupled system composed of veins and membranes, exhibiting significant directional variations in stiffness distribution. Calculating force and deformation under dynamic conditions is challenging but remains critical for aerodynamic optimization of flapping-wing aircraft. This study developed a rigid-flexible coupled wing design method inspired by butterfly wings, integrating parametric modeling, anisotropic stiffness optimization, and bidirectional Fluid-structure Interaction (FSI) simulation to quantify unsteady interactions and enable passive deformation for enhanced performance. A parametric model of butterfly wings was established using Bézier curves to describe diverse shape characteristics across butterfly families, linking biological morphology to aerodynamic properties. By defining and adjusting the spanwise and chordwise stiffness distribution of the wings, we analyzed the deformation and forces through simulation, revealing how adaptive bending guide Leading-edge Vortex (LEV) and improve thrust. We found that for a monarch butterfly with a 50 mm span, maintaining a chordwise stiffness of 0.154 N/m and a spanwise stiffness of 1.792 N/m results in excellent aerodynamic efficiency, generating thrust 6 times the wing’s weight—outperforming rigid wings by 34%. Based on this, a bionic butterfly MAV was designed and manufactured, achieving a thrust 1.3 times its own weight in free flight at 3.4 m/s, demonstrating the feasibility and scalability of this design method for robotic applications.

Key words: Flapping flight')">Flapping flight, Bionic butterfly, Biomimetics, MAV