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    Gust Response Predictions of a Very Flexible Wing Model
    (AIAA, 2025) Düssler, S. ; Mertens, C. ; Palacios, R.
    Nonlinear aeroelastic simulations are benchmarked against wind tunnel experiments of a very flexible wing. In the simulations, sectional force corrections are employed to capture low-Reynolds-number effects and the static lift deficiency due to the onset of flow separation. With these corrections, both the static and dynamic wing deformation predictions match the experiments well (2% and 6% error, respectively). Furthermore, a simulation of the unsteady inflow to the Delft-Pazy wing that is produced by the gust vanes in the wind tunnel is explored as an alternative to a frozen gust model. Results indicate a considerable influence of the wing’s presence on the gust velocity that was measured upstream of the wing in the wind tunnel experiment. The structural response, however, differs only slightly when using the two different gust models. This confirms that the uniform gust is still a valid assumption for moderately large deflections (up to 24% of the wingspan in this work). Finally, geometrically nonlinear effects are assessed and found to be relevant in the simulations because of the nonlinear aeroelastic equilibrium, but not because of the gust excitation.
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    Recovery from startle and surprise: A survey of airline pilots' operational experience using a startle and surprise management method
    (Elsevier, 2025) Vlaskamp, D. ; Landman, A. ; Rooij, J.M. van ; Blundell, J.
    A significant safety challenge airline pilots contend with is the possibility of experiencing startle and surprise. These are cognitive-emotional responses that may temporarily impair performance and that have contributed to multiple fatal loss of control events. Several self-management methods exist that are intended to facilitate recovery from startle and surprise, but these have only been tested in simulator experiments. The current study addresses this research gap by surveying the perceptions of 239 airline pilots on the utility and benefit of a method which they use in operational practice– the “Reset Method”. Overall, the survey results revealed that pilots felt the method improved mental preparedness, and reduced stress. A reported reason for not applying the method was the urge to act quickly. In addition, not all steps of the method were applied equally, and some pilots found the method difficult to fit into the existing procedures of several time-critical scenarios (e.g., aircraft upsets and emergency landings). We recommend training self-management methods in scenarios which carry the most risk of negative effects of startle and surprise. We also recommend instilling awareness of the ‘startle paradox': self-management techniques are most difficult to apply in situations where they are most beneficial. Method shortening and simplification may facilitate application. Future research should focus on refining the method's implementation, addressing the startle paradox, and understanding the transferability of startle and surprise management methods to other safety critical industries defined by complex sociotechnical interactions.
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    Characterization of thermal properties of ball-milled copper-graphene powder as feedstock for additive manufacturing
    (Elsevier, 2025) Lee, H. ; Jafari, D. ; Koutsioukis, A. ; Nicolosi, V. ; Geurts, B.J. ; Wits, W.W.
    Thermal properties of novel powder feedstocks, such as copper-graphene, remain largely unexplored despite their importance in heat dissipation and manufacturability in powder bed-based additive manufacturing (AM) processes. Therefore, this study characterizes the thermal properties of copper, graphene, and copper-graphene composite powder beds produced via ball milling (BM) using differential scanning calorimetry (DSC). Results reveal that BM reduces the effective thermal conductivity (ETC) up to ∼44 % for copper and ∼ 70 % for graphene powders. This is primarily due to the changes in particle morphology and the resulting modification in particle aspect ratio. Similar observations apply if copper and graphene are mixed, with up to ∼33 % reduction in ETC. This reduction is however attributed to the surface modification of the graphene-coated copper particle, providing a smaller contact radius compared to spherical copper and BM copper. This results in less effective heat conduction across the composite powder particle. Additionally, heat conduction through powder beds is analyzed by comparing the measured data with established thermal models, including Maxwell-Garnett approximation and thermal resistance network models. We demonstrate that microstructural modifications in powder beds, driven by particle morphology and surface modifications, substantially impact the ETC of copper-graphene composite powder beds.
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    Metal multi-material additive manufacturing : Overcoming barriers to implementation
    (Elsevier, 2025) Clare, A.T. ; Woizeschke, P. ; Rankouhi, B. ; Pfefferkorn, F.E. ; Bartels, D. ; Schmidt, M. ; Wits, W.W.
    Additive manufacturing has advanced rapidly since its origins in the 1980s. While some processes are now commercially viable, others remain experimental. A key ambition has been to combine multiple materials in a single part, enabling novel properties and overcoming traditional limitations of fabrication and assembly. Multi-material additive manufacturing offers a potential step change across industries, though scaling from lab to industry remains a challenge. This work explores the enabling technologies and science behind metal multi-material additive manufacturing and proposes how the research community can advance these innovations for meaningful industrial impact.
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    Analysis of Radar Absorbing FSS on Foldcores and Honeycombs
    (Scipedia, 2019) Es, J.J.P. van ; Hulzinga, A. ; Tensen, P. ; Schippers, H. ; Heijmans, R.M.H. ; Journee, M.J.G.
    The objective of the paper is to investigate the radar absorption of honeycombs and foldcores with printed conductive patterns. These structures can be manufactured by first printing conductive Frequency Selective Surfaces (FSS) on planar substrates, which then can be used to shape foldcores and honeycombs by means of specific manufacturing technologies. Foldcores can be considered as intermediate shapes between planar sheets (where the printed patterns are perpendicular to the impinging radar waves) and honeycombs (where the printed patterns are parallel to the impinging radar wave). It is shown that the radar absorbing properties of the design strongly depend on the electrical conductivity of the paint, the size of the printed patterns and the orientation of the printed patterns with respect to the impinging wave. It is shown that a planar FSS has a maximum absorption of 50%, while foldcores and honeycombs may obtain a higher absorption due to the fact that the patterns are orientated under an angle with respect to the propagation direction of the wave.