The present study was performed in the field of high-performance aerospace structures made of composite materials. I conducted the research here reported during a stage period at Messier-Dowty, in the context of the TIME collaboration project between Politectnico di Milano and ENSICA Ecole of Toulouse. Messier-Dowty, a company belonging to the Safran group, is a world leader in the field of is the world leader in the design, development, manufacture and support of air-craft landing gear systems. The objectives of the present work are: to propose finite element0 meshing methods to be used in the pre-design of braces in view of the upcoming Boeing 787-9; to examine the solution proposed by Messier-Dowty concerning the bushing concept, using a theoretical approach to be validated with finite element models; and to propose a new strategy to simulate bush fitting analysis process by finite element modelling (for the certification analysis of the B787-9). In particular, the study refers to the design phase of the main landing gear of Boeing 787-8 as made by Messier-Dowty SA and especially to its composite braces. The main objectives of this work were: first,to propose finite element methods to be used in the pre-design of braces in view of the upcoming Boeing 787-9; secondly, to examine the solution proposed by Messier-Dowty concerning the bushing concept, using a theoretical approach to be validated with finite element models; finally, to propose a new strategy to simulate bush fitting analysis step for the certification analysis of the B787-9. This work allowed to identify the optimal mesh seed to be imposed to composite braces meshed with tetrahedrons, so to obtain results compared to those achievable with hexahedrons ones. In addition a a new calculation strategy (to be used for the following finite element analysis) has been proposed, allowing to reduce CPU Time up to 25%.
La presente tesi é stata svolta nel campo delle strutture aeronautiche ad alte prestazioni realizzate in materiali compositi. La tesi é frutto del lavoro svolto nell’ambito del progetto di collaborazione TIME tra il Politectico di Milano e l’Ecole ENSICA di Toulouse, presso la Società francese Messier-Dowty, del gruppo Safran, leader mondiale nel campo della progettazione e costruzione di sistemi di atterraggio di aeromobili. In modo particolare, il lavoro svolto ha avuto come oggetto di studio le due parti strutturali di sostegno (braces), che uniscono il cilindro interno dei carrelli di atterraggio in titanio cui sono collegate le ruote e l’ammortizzatore, al resto della fusoliera del Boeing 787. Lo scopo della ricerca é stato triplice: in primo luogo, proporre dei metodi di calcolo applicabili agli elementi finiti tetraedrici da utilizzare nelle fasi di progettazione dei braces del futuro Boeing 787-9; in secondo termine, rivedere la soluzione proposta da Messier-Dowty per le giunzioni brace-brace e fusoliera-brace, realizzate tramite un sistema di doppia boccola e manicotto, alla luce di un approccio teorico da validare con modelli ad elementi finiti e test in laboratorio; in ultimo, unire le competenze acquisite durante le due precedenti fasi, per proporre una nuova strategia di simulazione numerica del processo di installazione del manicotto e delle boccole nell’alesaggio in composito (lug) per le fasi di calcolo di certificazione. Il lavoro ha portato a identificare le taglie ottimali di maglia da imporre ad ogni zona della struttura considerata per avere risultati comparabili con quelli ottenuti con elementi finiti esaedrici. Inoltre é stata presentata una nuova strategia di calcolo che permette di ridurre il tempo CPU del 25% rispetto alla procedura attualmente adottata.
Finite element methods for the modeling of Boeing B787 composite braces
FIORE, FRANCESCO
2009/2010
Abstract
The present study was performed in the field of high-performance aerospace structures made of composite materials. I conducted the research here reported during a stage period at Messier-Dowty, in the context of the TIME collaboration project between Politectnico di Milano and ENSICA Ecole of Toulouse. Messier-Dowty, a company belonging to the Safran group, is a world leader in the field of is the world leader in the design, development, manufacture and support of air-craft landing gear systems. The objectives of the present work are: to propose finite element0 meshing methods to be used in the pre-design of braces in view of the upcoming Boeing 787-9; to examine the solution proposed by Messier-Dowty concerning the bushing concept, using a theoretical approach to be validated with finite element models; and to propose a new strategy to simulate bush fitting analysis process by finite element modelling (for the certification analysis of the B787-9). In particular, the study refers to the design phase of the main landing gear of Boeing 787-8 as made by Messier-Dowty SA and especially to its composite braces. The main objectives of this work were: first,to propose finite element methods to be used in the pre-design of braces in view of the upcoming Boeing 787-9; secondly, to examine the solution proposed by Messier-Dowty concerning the bushing concept, using a theoretical approach to be validated with finite element models; finally, to propose a new strategy to simulate bush fitting analysis step for the certification analysis of the B787-9. This work allowed to identify the optimal mesh seed to be imposed to composite braces meshed with tetrahedrons, so to obtain results compared to those achievable with hexahedrons ones. In addition a a new calculation strategy (to be used for the following finite element analysis) has been proposed, allowing to reduce CPU Time up to 25%.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/10401