Methodologies for aircraft structural modeling in dynamic analysis

This thesis presents the work I produced during my visit to a company that designs, tests, and certifies aircraft, while supporting the structural department. The project focused on designing against flutter for the second prototype of a civil cargo drone. Attention was focused on the geometrical modelling of aircraft to support design and structural analysis. This process aims to certify the vehicle under EASA SC-VTOL or EASA SC-Light UAS regulations, ensuring that the aircraft's flight envelope is free of flutter. The 3D solid FEM model developed in-house by the company is reduced to a line/bar idealization using the basic theory of elasticity. The equivalent properties are obtained from static analyses of single components and assigned to BAR elements specifically created in FEM, which resemble the geometry of the original model. Lumped masses are representative of the mass properties, while connections between the reduced members are modeled as spring elements. To validate the procedure and improve fidelity, two experimental GVTs were performed, one on the isolated boom and one on the complete aircraft. The results are employed by a semi-automatic process of correlation with the purpose of improving the representation of modal shapes and matching the natural frequencies of the structure. The final objective is the creation of a representative discrete model that will be devoted to the formulation of flutter simulation, required before the flight test for certification. This standard methodology employed in the aerospace industry aims to reduce computational costs while preserving the fidelity of results applicable to the design optimization process. These analyses provide the basis for planning the aircraft's flight flutter test.