Topical Collection "Adaptive/Smart Structures and Multifunctional Materials in Aerospace"

Editors

Guest Editor
Dr. Rafic Ajaj

Department of Mechanical Engineering, College of Engineering, United Arab Emirates University, 15551 Al Ain, UAE
Website | E-Mail
Phone: +44 (0) 238 059 2453
Interests: morphing aircraft; aircraft design; adaptive/smart structures; aircraft structures; UAVs; acoustic fatigue
Guest Editor
Prof. Dr. Norman M. Wereley

Department of Aerospace Engineering, University of Maryland, 3179J Martin Hall, College Park, MD 20742 USA
Website | E-Mail
Phone: 301-405-1927
Interests: smart materials and structures; actuators; sensors; dampers; energy absorbers; pneumatic artificial muscles; control systems; applications to aircraft, ground vehicles, and robotic systems

Topical Collection Information

Dear Colleagues,

Recent advances in smart structures and multifunctional materials have facilitated many novel aerospace technologies such as morphing aircraft. A morphing aircraft, bio-inspired by natural fliers, has gained a lot of interest as a potential technology to meet the ambitious goals of the Advisory Council for Aeronautics Research in Europe (ACARE) Vision 2020 and the FlightPath 2050 documents. A morphing aircraft continuously adjusts its wing geometry to enhance flight performance, control authority, and multi-mission capability.

In the last 30 years, there have been a number of international research programmes and projects on morphing wings. Many of these programmes are still active, especially in Europe. These programmes/projects have developed many adaptive/smart structures to allow large and small shape changes and they have investigated multifunctional materials to act as actuators and/or sensors. Furthermore, adaptive structures and multifunctional materials have been used to design compliant skins which are one of the main challenges of morphing wings. These skins have to be flexible in the morphing direction but rigid in other directions to maintain the aerodynamic shape of the wing and withstand the aerodynamic loads. The other main challenge facing morphing aircraft is the ability to design light weight, stiff, and robust adaptive structures that require minimal actuation power.

The use of adaptive/smart structures and multifunctional materials is not limited to morphing aircraft but has been used extensively in other fields, such as structural health monitoring, energy harvesting, suspension systems, wind-turbine blades, and many others. Therefore, we invite papers either addressing the research opportunities outlined here, or in the general topic area of adaptive/smart structures and multifunctional materials that will make a substantive contribution to the state of the art in aerospace area.

Dr. Rafic Ajaj
Prof. Dr. Norman M. Wereley
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Aerospace is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 550 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • adaptive structures
  • multifunctional materials
  • morphing aircraft
  • actuators
  • sensors
  • energy harvesting
  • structural health monitoring
  • suspension systems
  • wind-turbine blades
  • compliant skins

Related Special Issues

Published Papers (3 papers)

2018

Jump to: 2017

Open AccessArticle Pneumatically Powered Drilling of Carbon Fibre Composites Using Synthetic Biodegradable Lubricating Oil: An Experimental Study
Received: 27 November 2017 / Revised: 7 January 2018 / Accepted: 11 January 2018 / Published: 16 January 2018
PDF Full-text (4085 KB) | HTML Full-text | XML Full-text
Abstract
Carbon fibre composites are a key component of aircraft structures because of their enhanced material properties such as favourable strength to weight ratios when compared to metal alloys. During the assembly process of an aircraft, carbon fibre components are joined to other structures
[...] Read more.
Carbon fibre composites are a key component of aircraft structures because of their enhanced material properties such as favourable strength to weight ratios when compared to metal alloys. During the assembly process of an aircraft, carbon fibre components are joined to other structures using rivets, bolts, and fasteners, and as part of the joining process, the components will need to be machined or drilled. Unlike metal alloys, composites are sensitive to heat and are vulnerable to internal structural damage from machining tools. They are also susceptible to a reduction in strength when fibres are exposed to moisture. In the machining process, carbon fibre composites may be drilled using oils to lubricate carbide machining tools. In this study, a description of the experimental apparatus is provided along with an investigation to determine the influence synthetic biodegradable lubricating oil has on drill rotational speed, drilling load, and drilling temperature when using a pneumatic drill to machine carbon fibre composite material. Full article
Figures

Graphical abstract

2017

Jump to: 2018

Open AccessArticle Design, Development and Testing of Shape Shifting Wing Model
Received: 19 August 2017 / Revised: 20 October 2017 / Accepted: 30 October 2017 / Published: 1 November 2017
Cited by 2 | PDF Full-text (9566 KB) | HTML Full-text | XML Full-text
Abstract
The design and development of morphing (shape shifting) aircraft wings—an innovative technology that has the potential to increase the aerodynamic efficiency and reduce noise signatures of aircrafts—was carried out. This research was focused on reducing lift-induced drag at the flaps of the aerofoil
[...] Read more.
The design and development of morphing (shape shifting) aircraft wings—an innovative technology that has the potential to increase the aerodynamic efficiency and reduce noise signatures of aircrafts—was carried out. This research was focused on reducing lift-induced drag at the flaps of the aerofoil and to improve the design to achieve the optimum aerodynamic efficiency. Simulation revealed a 10.8% coefficient of lift increase for the initial morphing wing and 15.4% for the optimized morphing wing as compared to conventional wing design. At angles of attack of 0, 5, 10 and 15 degrees, the optimized wing has an increase in lift-to-drag ratio of 18.3%, 10.5%, 10.6% and 4% respectively when compared with the conventional wing. Simulations also showed that there is a significant improvement on pressure distribution over the lower surface of the morphing wing aerofoil. The increase in flow smoothness and reduction in vortex size reduced pressure drag along the trailing edge of the wing as a result an increase in pressure on the lower surface was experienced. A morphing wing reduced the size of the vortices and therefore the noise levels measured were reduced by up to 50%. Full article
Figures

Graphical abstract

Open AccessArticle Numerical and Experimental Investigations of an Elasto-Flexible Membrane Wing at a Reynolds Number of 280,000
Received: 6 July 2017 / Revised: 24 July 2017 / Accepted: 24 July 2017 / Published: 27 July 2017
PDF Full-text (4083 KB) | HTML Full-text | XML Full-text
Abstract
This work presents numerical and experimental investigations of an elasto-flexible membrane wing at a Reynolds number of 280,000. Such a concept has the capacity to adapt itself to the incoming flow offering a wider range of the flight envelope. This adaptation is clearly
[...] Read more.
This work presents numerical and experimental investigations of an elasto-flexible membrane wing at a Reynolds number of 280,000. Such a concept has the capacity to adapt itself to the incoming flow offering a wider range of the flight envelope. This adaptation is clearly observed in the numerical study: the camber of the airfoil changes with the dynamic pressure and the angle of attack, which permits a smoother and delayed stall. The numerical results, obtained from Fluid Structure Interaction (FSI) simulations, also show that the laminar-turbulent transition influences the aerodynamic characteristics of the wing, as it directly affects the pressure distribution on the membrane and the geometry of the airfoil. Two different turbulence models were therefore tested. Furthermore, experimental investigations are considered in this paper to estimate the precision of the FSI simulations. It appears that the FSI study overestimates the lift coefficient, and the drag coefficient is undervalued, which can be explained by dynamic calibration of the model. Nevertheless, the velocity field obtained with the hot-wire anemometry system shows good agreement on the upper side of the model. The membrane deflection measurements also appear to be consistent with the expected geometry of the deformed airfoil from the FSI simulations. Full article
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Figure 1

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Ground Dynamic Characterization of a Fully Electrically Actuated Bi-Modal Morphing Flap
Author: Maurizio Arena, Francesco Amoroso and Rosario Pecora
Affiliation: Department of Industrial Engineering (Aerospace Section), University of Naples “Federico II”, Via Claudio, 21 -80125- Napoli (NA), Italy
Abstract: An adaptive structure is the integration of increasingly innovative technologies: reliable kinematic mechanisms, embedded servo-actuation and control systems are designed in order to assure a device fully compatible with stringent airworthiness requirements. A true-scale segment of the outer wing flap, addressed to the next generation green regional aircraft, 130-seats with open rotor configuration, was selected as test article for these investigation purposes. Such smart structural concept (4 meters span with a mean chord of 0.9 meters), conceived within JTI – Clean Sky EU Project, was designed in order to enable two different morphing modes on the basis of the A/C flight condition as well as the flap setting:

  • Mode 1: Overall camber morphing to enhance high-lift performances during take-off and landing (flap deployed);
  • Mode 2: Tab-like morphing mode for load control. Upwards and downwards deflection of the flap tip during cruise (flap stowed) for load control at high speed.

The specific study within the present paper aimed at investigating the dynamic performance of the morphing structure through the identification of the most significant low-frequency normal modes. The modal behaviour characterization of an aircraft represents, as known, an important early design stage for aero-servo-elastic issue, but especially for an adaptive system whose structural configuration might highly change during the flight. When dealing with the design of morphing wings, conventional structural arrangements are commonly replaced by innovative solutions enabling shape changes through actively controlled elasticity or mechanical systems. A particular attention has been given to the modal identification of the trim tab, being more exposed to dynamic vibrations at very high speed, which may lead to flutter coupling mechanism than the whole flap, always stowed during aircraft cruise phase. Often the generalized masses were determined only theoretically, starting from the discrete inertial model of the structure. In this study, instead, generalized masses associated at main mode shapes of load-control tab have been estimated by experimental way, implementing a few sensors based network with a controlled excitation. Such research activity deals then with the experimental-numerical validation of a structural model representative of the true scale flap segment. Further studies will be devoted to perform aero-servo-elastic sensitivity analyses integrating the innovative concept onto a large aircraft (i.e. CS-25 class) wing. Relying upon the good correlation level with test evidence, the numerical model represented certainly an appropriate tool for simulating hereafter critical operating scenarios.
Keywords: Electro-mechanical actuator; Finite Element Model; Generalized Mass; Ground Vibration Test; Morphing device.

 

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