Staff publications (AA)

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Open Access
Adaptive UAV control with sensor and actuator faults recovery
(MDPI, 2025-03-01) Bekhiti, Abdellah; Souanef, Toufik; Toubakh, Houari; Horri, Nadjim; Kafi, Mohamed Redouane; Bouzid, Zakaria
This paper presents an adaptive fault-tolerant control strategy tailored for fixed-wing unmanned aerial vehicles (UAV) operating under adverse conditions such as icing. Using radial basis function neural networks and nonlinear dynamic inversion, the proposed framework effectively handles simultaneous actuator and sensor faults with arbitrary nonlinear dynamics caused by environmental effects, model uncertainties and external disturbances. A nonlinear disturbance observer is incorporated for accurate sensor fault detection and estimation, thereby enhancing the robustness of the control system. The integration of the radial basis function neural network enables an adaptive estimation of the faults, ensuring accurate fault compensation and system stability under challenging conditions. The observer is optimised to minimise the deviation of the closed-loop dynamics eigenvalues from the assigned eigenvalues and to approach unity observer steady-state gain. The stability of the control architecture is mathematically proven using Lyapunov analysis, and the performance of the approach is validated through numerical simulations on a six Degrees of Freedom fixed-wing unmanned aerial vehicles model. The results show superior performance and robustness to challenging fault scenarios. This research provides a comprehensive fault management solution that enhances the safety and reliability of unmanned aircraft operations in extreme environments.
Open Access
Advanced thermal imaging processing and deep learning integration for enhanced defect detection in carbon fiber-reinforced polymer laminates
(MDPI, 2025-03-25) Garcia Rosa, Renan; Pereira Barella, Bruno; Garcia Vargas, Iago; Tarpani, José Ricardo; Herrmann, Hans-Georg; Fernandes, Henrique
Carbon fiber-reinforced polymer (CFRP) laminates are widely used in aerospace, automotive, and infrastructure industries due to their high strength-to-weight ratio. However, defect detection in CFRP remains challenging, particularly in low signal-to-noise ratio (SNR) conditions. Conventional segmentation methods often struggle with noise interference and signal variations, leading to reduced detection accuracy. In this study, we evaluate the impact of thermal image preprocessing on improving defect segmentation in CFRP laminates inspected via pulsed thermography. Polynomial approximations and first- and second-order derivatives were applied to refine thermographic signals, enhancing defect visibility and SNR. The U-Net architecture was used to assess segmentation performance on datasets with and without preprocessing. The results demonstrated that preprocessing significantly improved defect detection, achieving an Intersection over Union (IoU) of 95% and an F1-Score of 99%, outperforming approaches without preprocessing. These findings emphasize the importance of preprocessing in enhancing segmentation accuracy and reliability, highlighting its potential for advancing non-destructive testing techniques across various industries.
Open Access
An experimental investigation into fracture resistance of carbon fibre sheet moulding compound
(Elsevier, 2025-06-26) Xu, Xiaodong; Kiat Lo, Darren Kong; Adi Satriya, Ilham Akbar; Zheng, Liyi
Carbon Fibre Sheet Moulding Compound (CF-SMC) is an attractive material due to its good formability and green credentials. However, there is a lack of reliable fracture data, posing challenges when analysing CF-SMC materials which already have built-in randomness. Fracture Resistance curves (R-curves) and their variability have not been reported before for CF-SMC materials. This knowledge gap in the literature is addressed through Double Cantilever Beam (DCB) and first End Loaded Split (ELS) tests on CF-SMC. This work also explains the toughening mechanisms in CF-SMC materials during interlaminar fracture. Under Mode I, the toughening mechanism is fibre bridging while it is crack migration for Mode II. The new R-curve data provides new insights into the interlaminar fracture behaviour of CF-SMC materials and can be used as invaluable inputs for their failure analyses.
Open Access
Assessment of a liquid hydrogen conditioning system for retrofitting on kerosene designed turbofans
(ASME , 2025-10-01) Rompokos, Pavlos; Kyritsis, Vasileios; Mourouzidis, Christos; Roumeliotis, Ioannis
As energy transition to alternative fuels for civil aviation is likely to be gradual, hydrogen’s first entry to service may be implemented on existing gas turbine engines. In this paper a novel liquid hydrogen conditioning system for retrofitting on kerosene designed geared turbofans is assessed in terms of performance and engine rematching. The aim of the analysis is to identify emerging requirements for the design of the fuel and thermal management system within the constraints of a certified engine design. The conditioning system proposed, an LH2 preheater, enables the control of the gaseous hydrogen temperature at combustor entry and consists of a secondary combustor and a heat exchanger. The examined configuration considers various bleed source locations within the engine to supply the preheater system. For performing the analysis, a kerosene fueled engine has been designed and suitable integrated models capable to simulate the retrofitted hydrogen fueled engine as well as the LH2 preheater operation have been developed. The system performance has been analyzed for the different bleed source locations identifying operating limits and performance changes. From all the examined bleed source positions, utilizing the by-pass duct minimizes the impact on component rematching and engine efficiency. Additionally, through a gas path geometry multiparametric analysis, it was found that by readjusting the capacity of the high-pressure turbine and the core nozzle area the certified limits can be met for the retrofitted engine.
Open Access
Energy optimization strategies for automatic tiltrotor electric vertical takeoff and landing aircraft
(AIAA, 2025-03-25) Kang, Namuk; Lu, Linghai; Whidborne, James F.
Open Access
Experimental investigation of unsteady fan-intake interactions using time-resolved stereoscopic particle image velocimetry
(Elsevier, 2025-07) Migliorini, Matteo; Zachos, Pavlos K.; MacManus, David G.; Giannouloudis, Alexandros
Understanding engine response to unsteady intake flow distortion is a crucial requirement to de-risk the development of novel aircraft configurations. This is more critical for configurations with highly embedded engines. Recent advances in non-intrusive, laser-based flow diagnostics demonstrated the ability to measure unsteady flows in convoluted intakes with high resolution in time and space. This work presents novel non-intrusive, unsteady flow measurements ahead of a fan rotor coupled to a convoluted diffusive intake. The fan rotor caused a local increase of the maximum levels of swirl intensity at the blade tip region, as well as flow re-distribution at the interface plane between the fan and the inlet duct compared to the baseline configuration with no fan in place. This contributed to the reduction of the overall swirl angle unsteadiness across the main flow distortion frequencies. This research presents a notable advance in unsteady fan-intake interaction characterisation. The work shows that high-resolution optical measurements offer notably better understanding of these complex aerodynamic interactions and have the potential to be part of larger scale, industrial testing programmes for future product development and certification.
Open Access
Fundamental concepts of boundary-layer ingestion propulsion
(American Institute of Aeronautics and Astronautics (AIAA), 2025-05-13) Lamprakis, Ioannis; Sanders, Drewan S.; Laskaridis, Panagiotis
This work further develops energy-based far-field methods by introducing Galilean covariance in work–energy relationships of flight. The novelty lies in how decomposition formulations are rederived from integral forms of the governing laws applicable to moving control volumes. It is shown that aerodynamic performance is best evaluated in a reference where the aircraft moves through the atmosphere. The advantages are clearly demonstrated through the formulation of a hypothesis on boundary-layer ingestion (BLI) power savings using a series of simplified flat plate–BLI propulsor configurations. This hypothesis links BLI power savings to the energy content within the boundary layer and the propulsor’s ability to attenuate the ingested boundary layer’s velocity profile. Extensive numerical studies on both laminar and turbulent flows are carried out to test this hypothesis, examining different levels of wake recovery achieved through a body force model propulsor with varying load distributions. Near-perfect wake attenuation is shown to yield maximum power savings, but only for higher-Reynolds-number flows, where the influence of aeropropulsive interference on upstream dissipation is minimal. The flat plate findings are extended to a 2D axisymmetric fuselage representation, where baroclinic losses become significant. A maximum power saving of around 8% is achievable at typical cruise conditions for a single-aisle passenger aircraft.
Open Access
Impact of high-aspect-ratio wing aircraft concepts on conventional tricycle landing gear integration
(SAE International, 2025-05-10) Martin, Raphaël; Stockford, Jack; Smith, Howard
To comply with the Paris Agreement targets set in 2015, significant reductions in aircraft emissions are required. This demands a fundamental shift in aircraft design. Therefore, it is essential to study how future aircraft designs will affect the integration and design of landing systems. This research project examines the landing gear issues that arise from adopting specific future aircraft configurations. The study focuses on two primary configurations: the high-aspect-ratio wing and the ultra-high-aspect-ratio wing, with selected aircraft concepts from Cranfield University as baselines. It investigates the design and integration of conventional landing systems into these new aircraft concepts, highlighting the limitations posed by the modified airframes. The selected concepts include either telescopic or trailing arm arrangements, with attachment points on the wings or fuselage. A methodology for preliminary sizing of landing systems is presented, emphasizing automation and determining key performance indicators to assess the suitability of each solution for different aircraft architectures. The challenges of these novel airframes highlight opportunities to move away from conventional solutions and explore unconventional methods of interfacing between the aircraft and the ground.
Open Access
Integrated power and thermal management system in a parallel hybrid-electric aircraft: an exploration of passive and active cooling and temperature control
(MDPI, 2025-03-13) Ouyang, Zeyu; Nikolaidis, Theoklis; Jafari, Soheil; Pontika, Evangelia
Hybrid-electric aircraft (HEAs) represent a promising solution for reducing fuel consumption and emissions. However, the additional heat loads generated by the electrical propulsion systems in HEAs can diminish these benefits. To address this, an integrated power and thermal management system (IPTMS) is essential to mitigate these challenges by optimizing the interaction between thermal management and power management. This paper presents a preliminary IPTMS design for a parallel HEA operating under International Standard Atmosphere (ISA) conditions. The design includes an evaluation of active cooling, passive cooling, and active temperature control strategies. The IPTMS accounts for heat loads from the engine system, including the generators, shaft bearings, and power gearboxes, as well as from the electrical propulsion system, such as motors, batteries, converters, and the electric bus. This study investigates the impact of battery power (BP) contribution to cooling power on required coolant pump power and induced ram air drag. A comparison of IPTMS performance under 0% and 100% BP conditions revealed that the magnitude of battery power contribution to cooling power does not significantly impact the thermal management system (TMS) performance due to the large disparity between the total battery power (maximum 950 kW) and the required cooling power (maximum 443 W). Additionally, it was determined that the motor-inverter loop accounts for 95% of the pump power and 97% of the ram air drag. These findings suggest that IPTMS optimization should prioritize the thermal domain, particularly the motor-inverter loop. This study provides new insights into IPTMS design for HEAs, paving the way for further exploration of IPTMS performance under various operating conditions and refinement of cooling strategies.
Open Access
Multidisciplinary design optimization of the NASA metallic and composite common research model wingbox: addressing static strength, stiffness, aeroelastic, and manufacturing constraints
(MDPI, 2025-06-01) Dababneh, Odeh; Kipouros, Timoleon; Whidborne, James F.
This study explores the multidisciplinary design optimization (MDO) of the NASA Common Research Model (CRM) wingbox, utilizing both metallic and composite materials while addressing various constraints, including static strength, stiffness, aeroelasticity, and manufacturing considerations. The primary load-bearing wing structure is designed with high structural fidelity, resulting in a higher number of structural elements representing the wingbox model. This increased complexity expands the design space due to a greater number of design variables, thereby enhancing the potential for identifying optimal design alternatives and improving mass estimation accuracy. Finite element analysis (FEA) combined with gradient-based design optimization techniques was employed to assess the mass of the metallic and composite wingbox configurations. The results demonstrate that the incorporation of composite materials into the CRM wingbox design achieves a structural mass reduction of approximately 17.4% compared to the metallic wingbox when flutter constraints are considered and a 23.4% reduction when flutter constraints are excluded. When considering flutter constraints, the composite wingbox exhibits a 5.6% reduction in structural mass and a 5.3% decrease in critical flutter speed. Despite the reduction in flutter speed, the design remains free from flutter instabilities within the operational flight envelope. Flutter analysis, conducted using the p-k method, confirmed that both the optimized metallic and composite wingboxes are free from flutter instabilities, with flutter speeds exceeding the critical threshold of 256 m/s. Additionally, free vibration and aeroelastic stability analyses reveal that the composite wingbox demonstrates higher natural frequencies compared to the metallic version, indicating that composite materials enhance dynamic response and reduce susceptibility to aeroelastic phenomena. Fuel mass was also found to significantly influence both natural frequencies and flutter characteristics, with the presence of fuel leading to a reduction in structural frequencies associated with wing bending.
Open Access
On residual tensile strength after lightning strikes
(Elsevier, 2025-07-01) Xu, Xiaodong; Millen, Scott L. J.; Mitchard, Daniel; Wisnom, Michael R.
The study of post lightning strike residual strength is still relatively underdeveloped in the literature. Different approaches including in-plane compression or flexural testing have been used, but in-plane tensile loading post-strike has not been studied in detail. Although previous attempts have been made to determine the residual strength using Compression-After-Lightning (CAL) tests on composite laminates, these have been limited and not readily applicable under tensile loads. Therefore, this work completes Tension-After-Lightning (TAL) testing at 75 kA on composite laminates, a more realistic peak current than previously reported for TAL tests, to assess the knock-down in strength post-strike. The measured average TAL failure stress was 716 MPa, a reduction of 23 % from the baseline tensile failure stress of 929 MPa in the literature. This confirms a similar knock-down factor reported at lower peak currents (e.g. 50 kA), but the new TAL specimen geometry ensures that the lightning damage is contained within both the lightning and TAL specimen widths. In addition, a new Finite Element (FE) based virtual test was conducted, considering 0° ply splitting, and validated with the TAL tests herein. The TAL simulation predicted the residual tensile failure stress well, within 6 % of the measured value.
Open Access
Performance evaluation approach for design space explorations of propulsive fuselage aircraft concepts
(Springer, 2025-04-01) Moirou, Nicolas G. M.; Sanders, Drewan S.
A promising architecture to enhance the performance of next-generation commercial aircraft involves embedding the propulsion system within the airframe, thereby capturing energy from the fuselage through boundary layer ingestion. However, in cases of strong aerodynamic coupling, traditional accounting methods break down, necessitating alternative approaches. The lack of consensus surrounding the interpretation and quantification of these benefits underscores the need for a unified assessment method. In this work, commonly used near-field momentum-based bookkeeping schemes are discussed and unified with a more holistic energy-based approach to evaluate aero-propulsive performance and facilitate more intuitive physical interpretations of the aerodynamics. The contribution of this work lies in the correction of the power balance, leading to the development of new metrics for assessing the efficiencies of both the aircraft and the boundary layer ingestion propulsion system. Notably, a surrogate for propulsive efficiency and limits to the power saving coefficient are given, which address inconsistencies present in the literature. Despite their application to an axi-symmetric propulsive fuselage, the metrics introduced are applicable to higher levels of representativity of propulsive fuselage concepts. The potential impact of this work is the transformation of established evaluation practices by employing these newly introduced metrics to assess aircraft and system efficiencies.
Open Access
Through-the-thickness z-pinning reinforcements to improve energy absorption capabilities of CFRP crash structures: numerical development
(Springer, 2025-01-01) De Biasio, A; Ghasemnejad, H
This study employs numerical methods to model through-the-thickness reinforcements in CFRP tubular structures under axial impact, investigating the influence of reinforcement configurations on crashworthiness performance. Experimental validation involves testing unpinned tubular structures to establish a baseline model. LS-DYNA finite element models simulate low-velocity axial impacts, incorporating energy-based tiebreak contacts or solid cohesive elements to describe interlaminar bridging. Through-the-thickness are introduced through a homogenous mesh system or locally refined mesh at pin locations. Various reinforced tube designs with different pin diameters and areal densities are examined to identify the optimal pinned design for crashworthiness. The research demonstrates numerically that pinning enhances crashworthiness performances in axial crushing of composite tubes.

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