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    Topology Optimization for Aircraft Applications Using Hybrid and Multi-Material Methods for Different Component Scales
    (MDPI, 2025) Brink, W.M. van den ; Koenis, T.P.A. ; Osinga, T. ; Montero Sistiaga, M.L.
    The aviation industry, responsible for a significant portion of global CO2 emissions, faces the need to transition to more sustainable aircraft. Electric aircraft driven by battery-powered propulsion and further structural weight reductions have emerged as potential solutions. This research presents structural topology optimization methods developed at the Netherlands Aerospace Centre using (1) a hybrid approach with different scales for aircraft design, from component to full-scale aircraft. Furthermore, (2) multi-material designs are being explored in combination with additive manufacturing technology. Method 1: At the full aircraft level, the study employed a preliminary design methodology that combines shell and solid elements in a 3D model utilizing Abaqus software 2023. A topology optimization was carried out with strain energy and weight as the design responses, subject to specified volume and symmetry constraints. Different aircraft configurations were investigated, including blended wing designs, with each impacting the load paths and structural performance. A start was made in translating the optimized design to actual aerospace features such as frames and Door-Surround Structures (DSS). Method 2: The ability to manufacture multi-material metal parts via additive manufacturing presents opportunities for the design of aircraft components and shows weight-saving potential. The multi-material topology optimization method is explored for a relevant aerospace wing component. The results revealed widespread possibilities for general topology optimization methods to be applied in aircraft structural design at different scales. Load paths can be identified and their integration into multi-disciplinary design optimization (MDO) is promising. Novel structural designs for blended wing aircraft can be obtained for multiple load-cases. This research addresses questions concerning the aircraft-level and component-level feasibility of optimized designs, optimization features, inertia relief, and mesh size influence. The findings show the potential to optimize battery-powered aircraft through innovative structural design, contributing to a potentially lower weight and further reductions in environmental impact. This study serves as a first step towards lightweight future electric aircraft design and underscores the importance of integrating innovative solutions to reduce the climate impact of the aviation industry.
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    Degradation of structural aircraft coatings in cyclic salt spray testing, outdoor exposure, and in-service environments
    (Springer, 2026) Cornet, A.J. ; Homborg, A.M. ; Hoen - Velterop, L. 't ; Mol, J.M.C.
    Developing accelerated exposure tests that accurately predict the in-service performance of structural aircraft coatings remains challenging, largely due to the complexity of simulating real-world environmental conditions without altering key degradation mechanisms. This study evaluated four different coating systems under various accelerated exposure tests and compared their degradation behavior to in-service performance. Coating degradation was characterized using electrochemical impedance spectroscopy, scanning electron microscopy, and attenuated total reflectance Fourier transform infrared spectroscopy. Under in-service conditions, failure was primarily driven by the leaching of corrosion inhibitors, while the polymer matrix degraded predominantly through hydrolysis and thermo-oxidation. In contrast, during outdoor- or cyclic salt spray exposure, inhibitor leaching remained a key contributor to coating degradation although polymer degradation was mainly caused by ultraviolet radiation or hydrolysis. These findings emphasize the challenge of replicating real-world degradation in laboratory settings. Additionally, anodized oxide layers containing polymers within their pores played a critical role in maintaining protection during early coating failure. Chromate-based systems restored barrier properties, likely through chromate adsorption on hydrolyzed products within the oxide pores. In comparison, praseodymium-based systems failed to restore protection, while lithium-based systems sustained protection through an intact polymer.
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    Autonomous Separation in U-Space: Assessing the Impact of Position Uncertainty
    (SESAR Joint Undertaking, 2024) Rahman, M.F. ; Vlaskin, A.V. ; Ellerbroek, J. ; Hoekstra, J.M.
    With the rapid increase in the use of Unmanned Aerial Systems (UAS) for commercial applications such as medical and parcel delivery, the need for safe airborne separation in airspace has become critical. This paper examines the impact of position uncertainty on autonomous separation methods within U-Space, a European Union initiative for managing drone traffic. The study focuses on evaluating various conflict resolution algorithms—specifically, Modified Voltage Potential (MVP) and Velocity Obstacle (VO) variations—under conditions of navigational uncertainty. Through Monte Carlo simulations using the BlueSky ATM simulator, position uncertainty stemming from Global Navigation Satellite Systems (GNSS) errors is modelled and analysed. The research compares the effectiveness of different conflict resolution strategies in preventing conflicts between UAS, measuring intrusion prevention rates and the closest point of approach during encounters. The results indicate that MVP provides superior performance in handling positional uncertainty, offering more robust conflict resolution capabilities than VObased methods. These findings are critical for ensuring the safe integration of UAS into increasingly congested airspace environments, guiding future developments in U-Space operations.