Morphing Technologies: Adaptive Ailerons

European Union is involving increasing amount of resources on research projects that will dramatically change the costs of building and operating aircraft in the near future. Morphing structures are a key to turn current airplanes to more efficient and versatile means of transport, operating into a wider range of flight conditions

Skin-spar failure detection of a composite winglet using FBG sensors

Abstract Winglets are introduced into modern aircraft to reduce wing aerodynamic drag and to consequently optimize the fuel burn per mission. In order to be aerodynamically effective, these devices are installed at the wing tip section; this wing region is generally characterized by relevant oscillations induced by flights maneuvers and gust. The present work is focused on the validation of a continuous monitoring system based on fiber Bragg grating sensors and frequency domain analysis to detect physical condition of a skin-spar bonding failure in a composite winglet for in-service purposes. Optical fibers are used as deformation sensors. Short Time Fast Fourier Transform (STFT) analysis is applied to analyze the occurrence of structural response deviations on the base of strain data. Obtained results showed high accuracy in estimating static and dynamic deformations and great potentials in detecting structural failure occurrences

A sensitivity analysis on the influence of the external constraints on the dynamic behaviour of a low pollutant emissions aircraft combustor-rig

Abstract The need to reduce pollutant emissions leads the engineers to design new aeronautic combustors characterized by lean burn at relatively low temperatures. This requirement can easily cause flame instability phenomena and consequent pressure pulsations which may seriously damage combustor's structure and/or compromise its fatigue life. Hence the need to study the combustor's structural dynamics and the interaction between elastic, thermal and acoustic phenomena. Finite element method represent a largely used and fairly reliable tool to address these studies; on the other hand, the idealization process may bring to results quite far from the reality whereas too simplifying assumptions are made. Constraints modelling represent a key-issue for all dynamic FE analyses; a wrong simulation of the constraints may indeed compromise entire analyses although running on very accurate and mesh-refined structural models. In this paper, a probabilistic approach to characterize the influence of external constraints on the modal behaviour of an aircraft combustor-rig is presented. The finite element model validation was performed at first by comparing numerical and experimental results for the free-free condition (no constraints). Once the model was validated, the effect of constraints elasticity on natural frequencies was investigated by means of a probabilistic design simulation (PDS); referring to a specific tool developed in the ANSYS®software, a preliminary statistical analysis was at performed via Monte-Carlo Simulation (MCS) method. The results were then correlated with the experimental ones via Response Surface Method (RSM)

Design and integration sensitivity of a morphing trailing edge on a reference airfoil: The effect on high-altitude long-endurance aircraft performance

Trailing edge modification is one of the most effective ways to achieve camber variations. Usual flaps and aileron implement this concept and allow facing the different needs related to take-off, landing, and maneuver operations. The extension of this idea to meet other necessities, less dramatic in terms of geometry change yet useful a lot to increase the aircraft performance, moves toward the so-called morphing architectures, a compact version of the formers and inserted within the frame of the smart structures’ design philosophy. Mechanic (whether compliant or kinematic), actuation and sensor systems, together with all the other devices necessary for its proper working, are embedded into the body envelope. After the successful experiences, gained inside the SARISTU (SmARt Intelligent Aircraft STrUctures) project where an adaptive trailing edge was developed with the aim of compensating the weight variations in a mediumsize commercial aircraft (for instance, occurring during cruise), the team herein exploits the defined architecture in the wing of a typical airfoil, used on high-altitude long-endurance aircraft such as the Global Hawk. Among the peculiarities of this kind of aerial vehicle, there is the long endurance, in turn, associated with a massive fuel storage (approximately around 50% of the total weight). A segmented, finger-like, rib layout is considered to physically implement the transition from the baseline airfoil to the target configurations. This article deals with an extensive estimation of the possible benefits related to the implementation of this device on that class of planes. Parametric aerodynamic analyses are performed to evaluate the effects of different architectural layouts (in-plane geometry extension) and different shape envelopes (namely, the rotation boundaries). Finally, the expected improvements in the global high-altitude long-endurance aircraft performance are evaluated, following the implementation of the referred morphing device

Multi-modal Morphing Wing Flaps for Next Generation Green Regional Aircraft: the Clean Sky Challenge

Regional aviation is an innovation-driven sector of paramount importance for the European Union economy. Large resources and efforts are currently spent through the CleanSky program for the development of an efficient air transport system characterized by a lower environmental impact and unequaled capabilities of ensuring safe and seamless mobility while complying with very demanding technological requirements. The Green Regional Aircraft (GRA) panel, active from 2006, aims to mature, validate and demonstrate green aeronautical technologies best fitting the regional aircraft that will fly from 2020 onwards with reference to specific and challenging domains: from advanced low-weight and high performance structures up to all-electric systems and bleed-less engine architectures, from low noise/high efficiency aerodynamic up to environmentally optimized missions and trajectories management. The development of such technologies addresses two different aircraft concepts, identified by two seat classes, 90-pax with Turboprop (TP) engine and 130-pax, in combination with advanced propulsion solutions, namely, the Geared Turbofan (GTF), the Advanced Turbofan (ATF) and the Open Rotor (OR) configuration. Within the framework of the Clean Sky program, and along nearly 10 years of research, the design and technological demonstration of a novel wing flap architecture was addressed. Research activities aimed at demonstrating the industrial feasibility of a morphing architecture enabling flap camber variation in compliance with the demanding safety requirements applicable to the next generation GRA in both open rotor and turboprop configurations. The driving motivation was found in the opportunity to replace a conventional double slotted flap with a single slotted morphing flap assuring improved high lift performances -in terms of maximum attainable lift coefficient and stall angle- while lowering emitted noise, fuel-burnt and deployment system complexity. Additional functionalities for load control and alleviation were then considered and enabled by a smart architecture allowing for an independent shape-control of the flap tip region during cruise. The entire process moving from concept definition up to the experimental qualification of true scale prototypes, characterized by global and multi-zone differential morphing capabilities, is here described with specific emphasis on the adopted design philosophy and implemented technological solutions. Paths to improvements are finally outlined in perspective of a low-term item certification and series production

SMA for Aeronautics

The aviation industry has achieved drastic improvements during the past few decades, thanks to research efforts and advances in technology. With increased emphasis on adaptability and multifunctionality, smart materials and adaptive structures are now common terms in the literature and have been investigated extensively in many research programs to explore enhanced capabilities in aeronautical and space applications. The use of smart materials such as shape memory alloys gives us the chance to design mechanical and aerospace structures for better system performance, such as low vibration, shape control, and structural health monitoring. Such technologies, transitioning rapidly from basic research to reliable applications with a certain profile of maturity, offer the possibility of expanding current structural functionalities or replacing existing ones in retrofit applications. © 2015 Elsevier Ltd. All rights reserved

CLEAN SKY - GRA, LOW NOISE CONFIGURATION DOMAIN (phases 2 and 3)

The Clean Sky is one of the Joint Technology Initiatives (JTI) launched by the EC in the FP8. It represent the most ambitious research program in Europe (approximate value: 1.6 B€) aiming at the greening of Aeronautics and Air Transport; 30-40% reduction of CO2 and NOX emissions and the halving of perceived noise around airports are both pursued through the integration of advanced technologies; validation of results is expected to be achieved in a multidisciplinary approach leading to full-scale ground and flight demonstrators. Technologies allowing for such step change are organized into six main themes, six Integrated Technology Demonstrators (ITD), that cover the broad range of R&T work. A "technological evaluator" - a set of models to predict the local and global ecological impact of the technologies being integrated - will allow independent analysis of the projects results as they unfold. The “Low Noise Configuration” project within the GRA ITD is pursuing a dual purpose: to assess technologies aimed at reducing airframe noise which during approach and landing phases (with engine power at minimum, high-lift devices deployed and undercarriage lowered) is a major contributor to the aircraft annoyance perceived by the resident population; to address technology innovation toward other paramount functions for a next generation, green regional aircraft: highly-efficient aerodynamics, including a Natural Laminar Flow (NLF) wing concept, to reduce fuel consumption and pollution at cruise condition; wing loading control to enhance aerodynamic efficiency in all flight conditions and, hence, to reduce fuel consumption and pollution over the whole mission also allowing for steeper initial climb, noise-abatement flight trajectories; wing loading alleviation to avoid any possible loads exceeding over structural design conditions and, hence, to optimize the wing structural design for weight savings. The domain work programme develops through several phases: from the definition of requirements & architectures (phase 1), through the assessment of enabling technologies and subsequent application studies , up to the final demonstrations (phase 2 and 3) of selected solutions

Flutter di Velivoli con comandi Fly By Wire e Non Linearità

Scopo di questa tesi è lo sviluppo di metodologie affidabili per l’esecuzione di analisi di flutter non lineare, applicabili a velivoli con comandi manuali e a velivoli con comandi Fly By Wire. Lo sforzo è mirato all’arricchimento del pacchetto, già a disposizione, di codici in house per l’analisi di flutter, mantenendone invariato l’approccio, che è quello che utilizza la tecnica della sottostrutturazione dinamica (extra modi). Tale approccio sarà esposto in dettaglio nel Capitolo 2 e rappresenta la costante di tutto ciò che sarà prodotto per il flutter non lineare, [1]. La ragione della scelta degli argomenti della tesi risiede nella necessità, ravvisata dal mondo industriale, di strumenti affidabili e veloci, che consentano di rispondere alle esigenze certificative sia di velivoli di piccole dimensioni che di velivoli di grandi dimensioni. Il cuore della tesi è costituito da tre capitoli (Capitolo 2, Capitolo 3, Capitolo 4), con livello incrementale di problematiche da affrontare. Nel Capitolo 2 si metterà a punto la tecnica del bilancio armonico per effettuare analisi di flutter nel dominio della frequenza per un velivolo di categoria EASA CS 23, in presenza di non linearità nel movimento d’alettone. Nel Capitolo 3 si scriveranno le equazioni del sistema aeroelastico in presenza di leggi di controllo o comandi servopotenziati, nell’ipotesi di linearità del sistema. Il metodo sarà applicato su due casi molto diversi tra loro: un velivolo sperimentale non convenzionale, nel quale sarà considerata la legge di controllo dell’elevatore (flutter a ciclo chiuso) e un velivolo di categoria business jet (EASA CS 25), nel quale sarà considerata la presenza del servoattuatore idraulico dell’elevatore, le cui equazioni sono esposte in APPENDICE A, [2]. Nel Capitolo 4 si utilizzerà l’approccio precedente (Cap. 2), introducendo però le equazioni non lineari della dinamica del servoattuatore idraulico, pervenendo quindi alla scrittura delle equazioni del flutter non lineare, che saranno risolte con integrazione nel tempo. Le analisi di flutter di routine sono condotte con l’ipotesi di linearità: gli spostamenti sono piccoli, le forze aerodinamiche sono proporzionali alla risposta e gli elementi del sistema di controllo rispondono linearmente con l’ampiezza dello spostamento. È noto tuttavia che nei sistemi reali sono presenti fenomeni non lineari sia dal punto di vista strutturale che dal punto di vista aerodinamico. Tali non linearità influenzano il comportamento aeroelastico del velivolo e le metodologie lineari non sono in grado di prevederlo con accuratezza. Le sorgenti di non linearità possono risiedere: nella struttura, ad esempio la rigidezza cubica degli attacchi dei motori, il gioco nelle superfici mobili, le rigidezze bilineari dovute alla presenza di spring tab o le non linearità distribuite dovute ai giunti meccanici, nell’aerodinamica, ad esempio nel regime transonico, in cui la posizione dell’onda d’urto dipende dalla risposta dell’ala, quindi vi è una relazione non lineare tra il movimento della struttura e le forze aerodinamiche su di essa agenti