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    Numerical prediction of impact damage in thick fabric composite laminates
    (Elsevier, 2025) Hoorn, N. van ; Turteltaub S.R. ; Kassapoglou, C. ; Brink, W.M. van den
    A simulation methodology for assessing the damage in thick fabric Carbon Fibre Reinforced Polymer (CFRP) composite laminates under low- and high-velocity impacts is presented. It encompasses steps for calibration, verification, and validation of the elastic and fracture material properties as well as determination of model parameters for the numerical simulations. Damage is modelled using a discrete fracture approach with cohesive interface elements that capture individual cracks occurring in and between plies. For computational efficiency, the method is implemented in a two-dimensional (2D) axi-symmetric model. Results from double-cantilever beam, end-notched flexure, and quasi-static indentation experiments align well with numerical simulations and serve to calibrate and verify the implementation of the discrete fracture approach. The methodology is extended to dynamic impact analysis to predict damage mechanisms, force–displacement histories, and is validated using test results. This methodology combines meaningful insight in the failure mechanisms with a manageable computational effort, achieving a factor 50 improvement compared to a benchmark. A parametric analysis summarised in failure maps relates damage mechanisms to impact energy, mass, and laminate thickness. The proposed methodology strikes a balance between computational efficiency and accuracy, making it a valuable tool for optimum design and certification of thick CFRP composite laminates under impact.
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    Final Design, Manufacturing and Testing of the Clean Sky 2 Distributed Electric Propulsion Scaled Flight Demonstrator D08 DEP-SFD
    (AIAA, 2024) Doll, C. ; Hoogreef, M. ; Iannelli, P. ; Jentink, H.W. ; Kierbel, D.
    Within the work package radical new aircraft configuration of Cleansky2 Large Passenger Aircraft, a benefit of more than 20% in fuel consumption and CO2 emission (one of CS2 top level objectives) could be achieved by using various Distributed (hybrid) Electric Propulsion DEP architectures on different more or less radical aircraft configurations. It has therefore been identified as a disruptive technology which shall be de-risked in terms of achievable performance during wind tunnel tests and in terms of handling qualities during flight tests. The electric architecture with typical magnitudes shall also be studied in more detail. As already presented during AIAA SciTech Forum and Exhibition 2023, the D08 Distributed Electric Propulsion DEP version of the D03 Scaled Flight Demonstrator has been designed, manufactured and ground tested from 2020 to May 2023. An incident during the last ground test in May 2023 caused the total loss of this demonstrator. After its analysis, it was decided to robustify the electric architecture by improving the batteries, the wiring, the protections and the monitoring. These changes in the electric architectures lead to structural changes like the shift of the emergency parachute and bigger access hatches. The remanufacturing of the DEP-SFD2 has started in September 2023 for an exhaustive integration test campaign and taxi tests in January and February 2024. At the moment, the qualification flight tests will take place in April 2024 and the mission flight tests in May 2024.
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    Results of the scaled flight demonstrator flight tests
    (ICAS, 2024) Schmollgruber, P. ; Tossaint, C. ; Iannelli, P. ; Jentink, H.W. ; Kierbel, D.
    Within the Large Passenger Aircraft Platform of the Clean Sky 2 Programme, a consortium led by ONERA including Airbus, CIRA and NLR completed a thorough validation of Scaled Flight Testing. This approach is complementary to conventional ground tests and numerical simulations to mature technologies or configurations affecting the aircraft dynamic behavior. After several years dedicated to theoretical studies related to scaling effects and the development of the Scaled Flight Demonstrator (SFD) - a dynamically scaled unmanned version of a known full-scale transport aircraft - the partners successfully carried out the Qualification Flight Tests in March-April 2022 in Deelen (NL) and Mission Flight Tests in October-November 2022 in Grottaglie (IT). This paper provides in a first part several details about this latter experimental campaign that required an important preparatory phase. The second part starts with a presentation of the parameter identification based on flight measurements that enabled a refinement of the demonstrator simulation tools. Subsequently, the section compares the SFD dynamic behavior against the one of the reference full-scale aircraft. With very little variations between the aircraft responses at both scales, the research activity concluded that the overall full scale aircraft behavior can be obtained accurately with a dynamically scaled model. This positive conclusion of the flight tests together with the various high-fidelity numerical simulations enabled Scaled Flight Testing to reach TRL 5 in January 2023.
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    Performance, Environmental, and Mobility Analysis of Large Capacity Fast Rotorcraft Configurations for the European Regional Air Traffic Market
    ( 2023) Declerck, L.M.A. ; Cruellas Bordes, M. ; Saias, C.A. ; Nalianda, D. ; Schreiner, B.D.J. ; Misté, G.A. ; Dal Monte, A. ; Benini, E. ; Junior, A.
    Fast, large rotorcraft are of interest in the future European air transport system due to their runway independent operation and potential mobility improvements for the passenger. Both a tiltrotor and a coaxial compound concept model were developed for a 70 passenger, 500 NM design mission that would compete with regional fixed-wing aircraft. These models were flown along virtual trajectories representing possible use-cases and assessed for environmental performance in comparison to an in-service baseline aircraft using comparable engine technology levels. Further, the travel time and mobility improvement available to the intermodal transport network through the inclusion of these concept rotorcraft was examined with promising results. Future work is suggested to address the shortfall in environmental performance.
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    Flexible aircraft flight dynamics identification from flight test data in unsteady conditions
    (NVvL, 2024) Jurisson, A. ; Eussen, B.J.G. ; Visser, C. de ; Breuker, R. de
    In this paper, a flight dynamics model was identified for a scaled Diana 2 glider aircraft that included the influences from its flexible structure and the delayed effects caused by unsteady aerodynamics. Flight tests were conducted to collect response measurements to various excitation manoeuvres. A method was developed to obtain the pole values for aerodynamic lag states from the flight test measurements. These poles characterise the delays in aerodynamic force and moment responses caused by unsteady aerodynamics and are necessary to be able to reconstruct the aerodynamic lag states. Ordinary least squares regression was applied to estimate the aerodynamic force and moment coefficients. The inclusion of structural modes and aerodynamic lag states led to improvements in the fitting accuracy, when compared to a rigid aircraft model with the largest improvement of 32% achieved for aircraft roll moment coefficient.