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Free vibration and flutter behaviour of metallic and composite aircraft using DSM and developments of dynamic stiffness matrices for structural elements with applications

Ananthapuvirajah, A. (2019). Free vibration and flutter behaviour of metallic and composite aircraft using DSM and developments of dynamic stiffness matrices for structural elements with applications. (Unpublished Doctoral thesis, City, University of London)

Abstract

This thesis focuses on two types of original research, of which the first one (Section A) can be categorised as applied or engineering research concerning the free vibration and flutter behaviour of metallic and composite aircraft whereas the second one (Section B) is focused on fundamental research, on the developments of the dynamic stiffness matrices and application for a range of structural elements of varying degrees of complexities. The main focus of the first part of the research is to use analytical methods through the application of in-house computer programs to determine stiffness properties (EI, GJ and K) and then to carry out free vibration analysis and flutter analysis. Stiffness analysis using both single and double cell idealisation of the wing is first carried out and then free vibration and flutter analysis behaviour is subsequently investigated in details. Both low fidelity model using bending-torsion coupled beam representation of the aircraft and high-fidelity model using FEMAP/NASTRAN in which the aircraft is idealised in detail using beam, plate and shell elements have been used. In the low fidelity model, of particular significance is the inclusion of the bending-torsion coupling stiffness which exists in composite wings. The scope of the investigation is broadened by carrying out wingonly as well as whole aircraft configurations. In this endeavour a detail parametric study is undertaken by changing significant aircraft parameters such as bending and torsion stiffnesses, fuselage mass and inertia, engine mass and its location. Three categories of aircraft namely sailplane, light aircraft trainer and transport airliners are analysed with significant conclusion drawn.

Alongside the above investigation, fundamental research on the dynamic stiffness formulation for a range of structural elements is also carried out. This includes functionally graded beams, cracked beams, Rayleigh-Love bars, Timoshenko beams and axial-bending coupled beams. In each case, the governing differential equations and associated natural boundary conditions are derived using Hamilton’s principle. The equations are solved in closed analytical form and explicit expressions for the dynamic stiffness coefficients were obtained using symbolic computations wherever possible. Finally, the dynamic stiffness matrices are developed by relating the amplitudes of the forces to those of the displacements. The Wittrick Williams algorithm is used to yield the natural frequencies and mode shapes. The results obtained are validated using published results.

Publication Type: Thesis (Doctoral)
Subjects: T Technology > TL Motor vehicles. Aeronautics. Astronautics
Departments: Doctoral Theses
Doctoral Theses > School of Mathematics, Computer Science and Engineering Doctoral Theses
Business School > Actuarial Science & Insurance > Actuarial Research Reports
School of Mathematics, Computer Science & Engineering > Engineering > Mechanical Engineering & Aeronautics
Date Deposited: 21 Aug 2020 14:30
URI: https://openaccess.city.ac.uk/id/eprint/24796
[img] Text - Accepted Version
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