Compliant vs Kinematic Morphing Architectures: Complementary or Alternatives?

Dear Colleagues,

Morphing systems have been extensively researched, with several achieving advanced technology levels and, in some cases, undergoing flight testing. In 2015, flight tests were conducted on the Gulfstream III jet within the Adaptive Compliant Trailing Edge project, a project led by NASA in partnership with Flexsys and the (US) AFRL, among others. These achievements follow a tradition whereby types of morphing architectures are widely studied and then undergo operational testing, as in the 1980s and 1990s when a mission-adaptive wing was mounted onto the F111. Following each successful trial, such an adaptive technology experiences a pause in experimental activities and is returned to development. At present, it can be stated that, although the feasibility of designing and deploying adaptive wings has been proven, certain aspects must be further investigated before these challenging systems can be really deployed in a context of regular aircraft and broadly exploited on the commercial market.

The need to fully develop this technology has become more urgent in recent years. With the scenario evolution, it has become not just a matter of further improving the already excellent state-of-the-art aircraft efficiency, but also of addressing new challenges proposed by the modified needs and demands of the air transport. The increased use of UAV, as well the expected rise of the urban air mobility, offer considerable benefits through systems capable of adapting the wing shape (which can extend to other aerodynamic surfaces, such us tail-planes) without reverting to standard, massive and bulky, hyperlift devices.

As the proposed architectures are investigated, it may be concluded that two kinds of logics are generally implemented: kinematic and compliant. Upon closer examination, it becomes clear that these arrangements are heavily contaminated by each other. The explanation is straightforward: while kinematic devices namely ensure the full controllability of the target shape, compliant systems aim to achieve a smooth geometry in any configuration. This allows them to fully utilize their adaptability to the greatest possible extent. At this stage, it is believed that engineering should ponder over a driving question for its future developments: can kinematic and compliant visions be merged into a single approach, or should their incompatibility be retained, each with their respective strengths and weaknesses? Perhaps the limitations hindering the full development of morphing systems can be summarized by the antagonistic perspectives these architectures have been historically drawn from; however, combining their positives through a stereoscopic fusion may reveal unforeseen opportunities that would otherwise remain out of reach.

This Special Issue wants to provide a further stimulus to researchers involved in this fascinating discipline, encouraging them to expose the value of kinematic or compliant morphing systems,  highlighting their peculiar advantages and limitations. Their contribution may inspire the development of novel strategies and finally amalgamate these systems, overcoming their inherent drawbacks while preserving their undiscussed potentialities. Where and if applicable, the use of smart materials should be considered as a possible key factor in ensuring adequate structural resistance and continuous shape variability.

Based on these considerations, articles on one or more of the following topics are mainly searched for:

• Morphing kinematic architectures;
• Morphing compliant architectures;
• Hybrid morphing kinematic-compliant architectures;
• Integrated morphing skins;
• Integrated actuator networks;
• Integrated sensor networks;
• Integrated control systems;
• Aeroelastic issues of adaptive aircraft;
• Performance of adaptive aircraft;
• Ground testing of morphing systems;
• Scaling issues of morphing systems;
• Fight testing of morphing systems;
• Integration of morphing architectures into aircraft systems;
• Requirements vs regulations;
• SWOT assessment of morphing systems;
• TRL assessment of morphing systems;
• FHA assessment of morphing systems.

Dr. Antonio Concilio
Dr. Cristian Vendittozzi
Dr. Rosario Pecora
Dr. Salvatore Ameduri
Dr. Yu Yang
Guest Editors

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