Low Fidelity and High Fidelity Structural Models for Hybrid Composite Aircraft Structures

This thesis extends advanced one-dimensional models derived from the use of the Carrera Unified Formulation (CUF) to a High-Fidelity modeling approach, which has been used to perform analyses of multi-component aeronautical structures guaranteeing a proper description of each component regarding geometry and material. Static analyses and free vibration analyses have been performed to validate the current CUF model for the studies of structures, which present multi-component nature, sweep angle and non-prismatic shape; subsequently, its capabilities have been exploited to investigate different aeronautical topics. At first, the model has been used for the free vibration analysis of damaged structures and the possible use of the behavior alterations for the damage detection. Thanks to the capability of the model to control the stiffness arbitrarily, several scenarios have been analyzed where the damage has been introduced, for example, in the whole component or at the local level. The layer-wise capability of the model has allowed a wide tailoring analysis of thin-walled boxes to be performed. It has been used to evaluate the free-vibration behaviors according to the lamination used in the structure. Moreover, these analyses have been used to explore the possible influences on the geometrical coupling effects due to sweep angle or tapered shapes, in order to mitigate or emphasize them. The model has also been extended to the study of Variable Angle Tow (VAT) composites characterized by curvilinear fibers. After the validation with results from the open literature, the possible advantages in the aeronautic field of this technology have been explored through vibrational analyses of prismatic thin-walled boxes. The results confirm the capabilities of the current model to deal with very complex aeronautical structures providing accurate results with a sensible reduction of the computational cost compared to the classical used FEM models. Its performances are also tested with a displacement analyses in the second part of this thesis, which presents the work done during the apprenticeship related to the research project TIVANO with the company Leonardo Finmeccanica – Aircraft division.