Advances in Technology Innovation, vol. 1, no. 1, 2016, pp. 13 - 15 13 Copyright © TAETI Composite Elements for Biomimetic Aerospace Structures with Progressive Shape Variation Capabilities Alessandro Airoldi * , Paolo Bettini, Matteo Boiocchi, Giuseppe Sala Department of Aerospace Science and Technologies, Politecnico di Milano, Italy Received 01 February 2016; received in revised form 11 March 2016; accepted 02 April 2016 Abstract The paper presents some engineering solutions for the development of innovative aerodynamic surfaces with the capability of progressive shape variation. A brief introduction of the most significant issues related to the design of such morphing structures is provided. Thereafter, two types of structural solutions are presented for the design of internal compliant structures and flexible external skins. The proposed solutions exploit the properties and the manufacturing techniques of long fibre reinforced plastic in order to fulfil the severe and contradictory requirements related to the trade-off between morphing performance and load carrying capabilities. Keywor ds : morphing structures, composite structures, chiral topologies, corrugated laminates 1. Introduction Morphing structures have been intensively studied in the last decades in the aerospace field, with the objective of developing innovative, more flexible and efficient methods to change the shape of aerodynamic surfaces. Imitation of nature plays an important role in conceiving such type of structures, since organisms have solved the problems related to flight control and adaptation to different flight phases without the use of rigid moveable surfaces, which are currently used in aircraft. For instance, a flexible wing with the capability of shape variation can increase the curvature, when higher lift is required at low velocity, whereas, at high speed, curvature can be reduced to decrease drag (1). Another concept , called “chiral sail” is proposed in (2) and is based on wing with a central morphing part that increases its camber when angle of attitude is changed (Fig. 1). This can lead to noticeable advantages for the surfaces that generate the forces for the stabilization of a vehicle, like the tail empennages of aircraft. Indeed, these surfaces could be reduced with overall weight saving and drag reduction. However, although morphing is an appealing concept, there are critical engineering issues to be solved for the development of such type of structures, which are hereby summarized in the following point: a) Compliance of structures must be finely tuned to accomplish shape variations induced by aerodynamic loads (passive morphing) or of actuators (active morphing). b) Shape can vary but must retain the aerodynamic efficiency, without angular points, surface waviness, and anomalous modification of profiles. c) Aerodynamic loads acting in morphing directions must be transmitted, so that morphing structures must exhibit flexibility and strength at the same time (passive morphing), or reacted by load bearing actuators (active morphing). d) Stiffness and strength in non-morphing directions must be maximized to avoid the need of additional structural parts that would increase structural weight, thus reducing or eliminating the advantages of morphing concepts. Fig. 1 Variable camber wing with central morphing part * Corresponding author, Email: alessandro.airoldi@polimi.it brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Taiwan Association of Engineering and Technology Innovation: E-Journals