Noviello, Maria Chiara (2018) Aeroelastic Stability Assessment Of a CS-25 Category Aircraft Equipped With Multi-Modal Wing Morphing Devices. [Tesi di dottorato]

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Tipologia del documento:	Tesi di dottorato
Lingua:	English
Titolo:	Aeroelastic Stability Assessment Of a CS-25 Category Aircraft Equipped With Multi-Modal Wing Morphing Devices
Autori:	Autore Email Noviello, Maria Chiara chiaranoviello@virgilio.it
Data:	10 Dicembre 2018
Numero di pagine:	148
Istituzione:	Università degli Studi di Napoli Federico II
Dipartimento:	Ingegneria Industriale
Dottorato:	Ingegneria industriale
Ciclo di dottorato:	31
Coordinatore del Corso di dottorato:	nome email Grassi, Michele michele.grassi@unina.it
Tutor:	nome email Marulo, Francesco [non definito] Lecce, Leonardo [non definito] Pecora, Rosario [non definito] Amoroso, Francesco [non definito] Concilio, Antonio [non definito] Dimino, Ignazio [non definito]
Data:	10 Dicembre 2018
Numero di pagine:	148
Parole chiave:	Aeroelasticity; Morphing wing structures; Morphing flap; Adaptive Winglet; Flutter; Fault and Hazard Assessment.
Settori scientifico-disciplinari del MIUR:	Area 09 - Ingegneria industriale e dell'informazione > ING-IND/04 - Costruzioni e strutture aerospaziali
Depositato il:	02 Gen 2019 15:26
Ultima modifica:	23 Giu 2020 14:30
URI:	http://www.fedoa.unina.it/id/eprint/12588

Abstract

Morphing wing structures have the greatest ambition to dramatically im-prove aircraft aerodynamic performance (less fuel consumption) and reduce aerodynamic noise. Several studies in the literature have shown their potential for increased aerodynamic efficiency across nearly all flight conditions, en-hanced aircraft maneuverability and control effectiveness, decreased take-off/landing length, reduced airframe noise, etc. However, despite a long herit-age of research, morphing wing technology has yet to be approved by the Euro-pean Aviation Safety Authority (EASA) for use in commercial aviation. Models and approaches capable to predict the aeroelastic impact of a morphing wing still need to be matured to safely alter design and operation of future genera-tions of aircraft. Additionally, a number of practical challenges remain to be addressed in the suitable materials, systems reliability, safety and maintenance. Due to the reduced stiffness, increased mass and increased Degree Of Freedom (DOF) with respect to conventional wings, these mechanical systems can cause significant reduction of aircraft flutter margins. This aspect requires dedicated aeroelastic assessments since the early stages of the design process of such an innovative wing. Flutter boundaries predictions need sensitivity anal-yses to evaluate bending/torsional stiffness and inertial distribution variability ranges of the aircraft wing equipped with the morphing wing devices. In such a way, aeroelastic assessments become fundamental to drive a balance between weight and stiffness of the investigated adaptive systems. Furthermore, in pseu-do rigid-body mechanisms-based morphing structures, the inner kinematics is so important that its faults may compromise the general aircraft-level functions. Similarly to the demonstration means of safety compliance, commonly applied to aircraft control surfaces, the novel functions resulting from the integration of adaptive devices into flying aircraft thus impose a detailed examination of the associated risks. In the framework of Clean Sky 2 Airgreen 2 project, the author provides advanced aeroelastic assessments of two adaptive devices enabling the camber morphing of winglets and flaps, conceived for regional aircraft integration (EASA CS-25 category). Segmented ribs architectures ensure the transition from the baseline (or un-morphed) shape to the morphed ones, driven by em-bedded electromechanical actuators. Some of the advantages resulting from the combination of the two aforementioned morphing systems are wing load con-trol, lift-over-drag ratio increase and root bending moment alleviation. The aircraft aeroelastic model was generated by means of the proprietary code SANDY 3.0. Then, the same code was adopted to solve the aeroelastic stability equa-tions through theoretical modes association in frequency domain. To carry out multi-parametric flutter analyses (P-K continuation method), the actuation lines stiffness and winglet/flap tabs inertial parameters were considered in combina-tion each other. Nominal operative conditions as well as systems malfunction-ing or failures were examined as analyses cases of the investigated morphing devices, together with actuators free-play conditions. Proper design solutions were suggested to guarantee flutter clearance in accordance with aircraft stabil-ity robustness with respect to morphing systems integration, evaluated through a combination of “worst cases” simulating the mutual interaction among the adaptive systems. The safety-driven design of the morphing wing devices required also a thorough examination of the potential hazards resulting from operational faults involving either the actuation chain, such as jamming, or the external interfaces, such as loss of power supplies and control lanes, and both. The main goal was to verify whether the morphing flap and winglet systems could comply with the standard civil flight safety regulations and airworthiness requirements (EASA CS25). More in detail, a comprehensive study of systems functions was firstly qualitatively performed at both subsystem and aircraft levels to identify poten-tial design faults, maintenance and crew faults, as well as external environment risks. The severity of the hazard effects was thus determined and then ranked in specific classes, indicative of the maximum tolerable probability of occurrence for a specific event, resulting in safety design objectives. Fault trees were final-ly produced to assess the compliance of the system architectures to the quanti-tative safety requirements resulting from the FHAs.

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