2D unsteady aeroelastic modeling and flutter prediction of composite wing for high-payload UAV competing in the air cargo challenge

The design of high-performance Unmanned Aerial Vehicles (UAVs) for competitions that require the maximization of the payload fraction, such as the Air Cargo Challenge (ACC), requires lightweight composite structures. However, the resulting mass-efficient wings possess reduced flexural and torsional rigidities, rendering them highly susceptible to dangerous fluid-structure interactions such as aeroelastic flutter. While low-fidelity aerodynamic tools neglect flow unsteadiness and high-fidelity Computational Fluid Dynamics (CFD) coupled with Finite Element Methods (FEM) remain computationally and time expensive, a clear need exists for a reliable mid-fidelity solver. This thesis presents the development of a mid-fidelity numerical tool designed to evaluate the flutter speed of "Midnight" wing, a fixed-wing drone designed and manufactured by the LiftUP Team (Student project based at the University of Padova). The aerodynamic solver consists of a two-dimensional Unsteady Vortex Panel Method (UVPM), built on MATLAB, that tracks transient aerodynamic phenomena by dynamically shedding a discrete vortex wake behind the wing's trailing edge. The aerodynamic tool is coupled with a discrete two-degrees-of-freedom (2DoF) structural solver to establish a predictive flutter environment. By modeling the structural characteristics and mass distributions of the full-carbon wing structure, the coupled system successfully maps the unsteady pressure distributions and the pitch and plunge motion of the airfoil in time. By simulating different airflow velocities, the critical flutter speed can be identified observing if the described motion is damped or if it diverges. The resulting solver provides a robust, computationally efficient tool that balances geometric flexibility with low execution time, serving as a vital asset for the definition of the flight envelope during the preliminary design of the UAV.