Search Results (80)

Predicting buckling in large-scale composite structures is hindered by the need for highly detailed Finite Element (FE) models, which are computationally expensive and impractical for early-stage design iterations. This study introduces a macromodelling buckling framework that reduces those models to plate-level size without sacrificing accuracy. An equivalent bending stiffness matrix is derived from strain–energy equivalence, rigorously retaining orthotropic in-plane terms, bending–extensional coupling, and—crucially—the eccentricity of compressive loads about an unsymmetrically stiffened mid-plane, effects overlooked by conventional Parallel-Axis smearing. These stiffness terms contribute to closed-form analytical solutions for homogeneous orthotropic plates, providing millisecond-level evaluations ideal for gradient-based design optimisation. The method is benchmarked against detailed FE simulations of panels with three to ten stringers under longitudinal and transverse compression, showing less than 5% deviation in critical load prediction. Its utility is demonstrated in the sizing optimisation of the upper cover of a scaled Airbus A330 composite wing-box, where the proposed model explores the design space in minutes on a standard workstation, orders of magnitude faster than full FE analyses. By combining analytical plate theory, enhanced smearing, and rapid optimisation capability, the framework provides an accurate, ultra-fast tool for buckling analysis and the preliminary design of large-scale stiffened composite structures. Full article

This research analyzes the discourses and narratives surrounding the platform tourism economy in a highly touristified city, using Madrid as a case study. Rather than focusing on the socio-economic or spatial transformations themselves, the study examines how these processes are discussed, identifying the discursive strategies employed by different actors and ideologies, along with the power relations embedded in these narratives. A corpus of literature was compiled from twelve newspapers with varying ideological orientations and categorized according to political stance, access mode, and ideological radicalism. Using the LancsBox concordancer, a quantitative analysis was conducted to identify key discursive categories and preferred lexical items across ideological positions. These findings informed a subsequent in-depth qualitative analysis aimed at uncovering the rationalities behind each discourse: who speaks, how, and with what intent. The results reveal a dominant left-wing narrative that emphasizes institutional and economic mechanisms underlying platform tourism, highlighting associated social and urban harms. In contrast, conservative and liberal narratives are divided into two strands: a ‘heretic’ discourse that promotes and defends this new economic model, but also its urban results (e.g., gentrification), and a more institutional narrative framing platform tourism as inevitable and benign, thereby concealing the underlying structures of power. Full article

In functionally graded polymer foam, mechanical properties and chemical composition vary in a prescribed direction according to a power law distribution. However, most manufacturing methods lack precise control over pore size, limiting their application. In this case, the graded foam structure can be formed from separate layers, with each layer assigned unique values in terms of mechanical properties or chemical composition based on the power law distribution. The hypothesis of the work is that the application of functionally graded (FG) foam materials inside the rotor blades or wings of an unmanned aerial vehicle can provide the ability to vary their stiffness properties. The aim of this work is to conduct an investigation of the static behaviour of a composite box plate with constant and variable heights that simulate the dimensions and changing profile of a helicopter rotor blade. In the numerical analysis, two models of composite box plate are considered and the material properties of graded polymeric foam core are assumed to vary continuously by the power law along the width of cross-sectional structures. It is not possible to model the continuous flow of graded properties through the foam in construction; therefore, the layers of foam are modelled using discontinuous gradients, where the gradient factor changes step by step. The numerical results are obtained using ANSYS software. The results of the numerical calculation showed that the use of graded foam affects the parameters under study. The stiffness of a structure significantly decreases with an increase in the power law index. Full article

Following the promising performance of the seamless morphing trailing edge (SMTE) flap and its internal actuation system, the elephant trunk mechanism (ETM), investigated through aerodynamic and structural analyses, this study presents an experimental analysis of the SMTE flap equipped with an elephant trunk actuation mechanism. The morphing wing model was prototyped using a 3D printer. Four elephant trunk morphing ribs were embedded inside the flap section, all covered with a flexible skin. The control system for flap actuation was installed in the wing box corresponding to four elephant trunk mechanisms using an appropriate graphical interface to control the SMTE flap deflections. The completed model was further tested in a subsonic wind tunnel to validate the numerical aerodynamic results, as well as the functionality of the elephant trunk mechanism in real conditions. The results confirm the reliability and practicability of the proposed elephant trunk mechanism for actuation, and a very good agreement was obtained between the numerical aerodynamic data and wind tunnel test results. Full article

A novel mechanism for seamless morphing trailing edge flaps is presented in this paper. This bio-inspired morphing concept is derived from an elephant’s trunk and is called the Elephant Trunk Mechanism (ETM). The structural flexibility of an elephant’s trunk and its ability to perform various types of deformations make it a promising choice in morphing technology for increasing the performance of continuous and smooth downward bending deformation at a trailing edge. This mechanism consists of a number of tooth-like elements attached to a solid wing box; the contractions of these tooth-like elements by external actuation forces change the trailing edge shape in the downwards direction. The main actuation forces are applied through wire ropes passing through tooth-like elements to generate the desired contractions on the flexible teeth. A static structural analysis using the Finite Element Method (FEM) is performed to examine this novel morphing concept and ensure its structural feasibility and stability. Topology optimization is also performed to find the optimum configuration with the objective of reducing the structural weight. The optimized mechanism is then attached to the flap section of a UAS-S45 wing. Finally, a skin analysis is performed to find its optimum skin material, which corresponds to the requirements of the morphing flap. The results of structural analysis and topology optimization reveal the reliability and stability of the proposed mechanism for application in the Seamless Morphing Trailing Edge (SMTE) flap. The optimization results led to significant improvements in the structural parameters, in addition to the desired weight reduction. The ETM maximum vertical displacement increased by 8.6%, while the von Mises stress decreased by 10.43%. Furthermore, the factor of safety improved from 1.3 to 1.5, thus indicating a safer design. The mass of the structure was reduced by 35.5%, achieving the primary goal of topology optimization. Full article

The current commitment towards aviation climate neutrality and decarbonisation is boosting research programmes on disruptive aircraft configurations featuring sustainable powertrains and fuel-efficient airframes. This trend is pushing the design towards high-aspect-ratio wings made of lightweight structures housing distributed propulsion systems. Airframe preliminary sizing and mass estimation of non-conventional configurations, if performed using legacy methodologies based on experience, gathered with traditional configurations may result in non-optimised and non-viable designs. Therefore, a physics-based optimisation approach may allow more accurate sizing and airframe mass estimation. The methodology suggested in this paper is based on the automatic generation of a global finite element model to estimate the weight and determine a feasible material distribution for the wing box structure of a strut-braced wing configuration by means of size optimisation. Composite materials with defined stacking sequences were assigned to the wing components and structural weight minimised with the aim of offsetting the weight penalties associated with this non-conventional aircraft configuration. Preliminary results suggest that the composite strut-braced wing could achieve a weight reduction of up to 44% compared to a composite cantilever wing with equal aspect ratio of 20. The actual weight reduction is thought to be lower due to potential overestimation of the cantilever configuration. Full article

This paper deals with the application of a novel fiber optic SHM system for bonding lines monitoring of a composite aircraft wing within Clean Sky 2 program framework. With the aim of controlling the structural state of the reference component, several targets may be addressed, including safety increase through a periodic update of the integrity level, maintenance costs reduction, for instance, by moving to an on-demand from the usual scheduled approach, and even design benefits by envisaging the possibility of modulating the safety coefficients due to an increased knowledge of the intimate structural system behavior. Specifically, an original SHM architecture is herein presented, based on the use of distributed optical fibers, and implementing a proprietary algorithm, to detect bonding lines damage. Ground testing with a full-scale wing box successfully validated the system’s capability to identify damage. To assess maturity, a TRL evaluation has been carried out, whose results are summarized and discussed. Such a process allowed us to highlight specific areas for technological improvement, such as modeling-testing synergy and operational environment definition. The work herein reported is expected to address these aspects while achieving full-scale aircraft integration, paving the way for enhanced structural robustness and operational safety in future aircraft. Full article

In view of the fact that the specification does not specify the calculation model for the temperature gradient of the concrete box-shaped arch rib without wing plates, and there is also a lack of relevant research on the temperature model of this type of arch rib, this paper carries out research on the impact of sunshine temperature on a section of concrete box arch rib without a flange plate based on the 355 m Shuiluohe Bridge. Firstly, a temperature experiment of the arch rib without flange plates was conducted. According to the experimental data, the temperature distribution and changing rules of the arch rib cross-section were analyzed. Then, according to the measured temperature data, a calculation mode of the vertical temperature gradient of the arch rib was proposed and compared with the specification. Finally, in view of the most disadvantageous phases of the arch rib in the construction process, the influence of different gradient modes on the structural mechanical behavior was analyzed by means of a simulation model. The results show that along the span from the springing to L/2, the maximal temperatures of the top plate, web plate and bottom plate gradually increase. The temperature gradient of the box’s top plate is the largest, that of the web plate is the second largest, and that of the bottom plate is the smallest. The vertical temperature difference of the key section of the arch rib gradually increases from the springing to L/2, and the maximal temperature difference of the section at L/2 is 16.3 °C, which is 4.2 °C higher than that of the springing section. The vertical temperature gradient proposed in this paper is a four-fold nonlinear model. Compared with the temperature gradient distribution range specified in the specification, the vertical temperature gradient in this article has a wider distribution range in the cross-section height, and the temperature varies more quickly along the cross-section height. The temperature gradient model proposed has more adverse effects on the mechanical behavior of the structure. The temperature gradient model proposed in this paper not only fills the gap in the specification but also provides suggestions for the design and construction of bridges. Meanwhile, the temperature distribution model of this type of arch rib also lays a theoretical foundation for the further development of corresponding thermal insulation materials for concrete surfaces or new concrete materials. Full article

In this paper, the status quo of manufacturing technology of the wing structures of large and small general aircraft at home and abroad is reported. The existing problems in the manufacturing technology of double-beam, multi-rib composite wing structures are analyzed. The application of adhesive co-curing technology to manufacture eVTOL double-beam, multi-rib integral composite wing box segment structures is proposed. Composite-material wing box segment adhesive co-curing manufacturing technology realizes the high-quality manufacturing of double-beam, multi-rib integral wing box segment structures and the optimal lightweight design of such structures. It can be applied to the manufacture of this type of integral wing box segment structure or the manufacture of other complex integral composite components. Full article

As the largest non-gravitational force, solar radiation pressure (SRP) causes significant errors in precise orbit determination (POD) of the BeiDou global navigation satellite system (BDS-3) medium Earth orbit (MEO) satellite. This is mainly due to the imperfect modeling of the satellite’s cuboid body. Since the BDS-3’s inter-satellite link (ISL) can enhance the orbit estimation of BDS-3 satellites, the aim of this study is to establish an a priori SRP model for the satellite body using 281-day ISL observations to reduce the systematic errors in the final orbits. The adjustable box wind (ABW) model is employed to refine the optical parameters for the satellite buses. The self-shadow effect caused by the search and rescue (SAR) antenna is considered. Satellite laser ranging (SLR), day-boundary discontinuity (DBD), and overlapping Allan deviation (OADEV) are utilized as indicators to assess the performance of the a priori model. With the a priori model developed by both ISL and ground observation, the slopes of SLR residual for the China Academy of Space Technology (CAST) and Shanghai Engineering Center for Microsatellites (SECM) satellites decrease from −0.097 cm/deg and 0.067 cm/deg to −0.004 cm/deg and −0.009 cm/deg, respectively. The standard deviation decreased by 21.8% and 26.6%, respectively. There are slight enhancements in the average values of DBD and OADEV, and a reduced β-dependent variation is observed in the OADEV of the corresponding clock offset. We also found that considering the SAR antenna only slightly improves the orbit accuracy. These results demonstrate that an a priori model established for the BDS-3 MEO satellite body can reduce the systematic errors in orbits, and the parameters estimated using both ISL and ground observation are superior to those estimated using only ground observation. Full article

The foldable tail of the box-type launch vehicle poses a risk of mechanical jamming during the launch process, which is not conducive to the smooth completion of the flight mission. The integrated nonfolding ducted tail proposed in this article can solve the problem of storing the tail in the launch box. Moreover, traditional mechanical control surfaces have been eliminated, and active jet control has been adopted to control the pitch direction of the flight attitude, which can improve the structural reliability of the tail wing. By studying the effects of parameters such as momentum coefficient, jet hole position, jet hole height, and jet angle on improving the aerodynamic performance of ducted tail wing, relatively good jet parameters are selected. Research has found that compared with jet hole height and jet angle, momentum coefficient and jet hole position are more effective in improving the aerodynamic performance of ducted tail wings. Under a trailing edge jet, a relatively good jet condition occurs when the jet hole height is equal to0.25% of the aerodynamic chord length, and the jet angle is equal to 0°. At this time, with the increase of the jet momentum coefficient, the effect of increasing the lift of the ducted tail wing is the best. Finally, a comparative analysis is conducted on the lift and drag characteristics between the ducted tail wing and traditional tail wing, and it is found that the ducted tail wing can generate lift at a 0° attack angle and will not stall in the high attack angle range of 12°~22°, with broad application prospects. Full article

Operational loads of an aircraft are the prerequisite for assessing its safety or fatigue life. Traditionally, numerous strain gauge sensors are installed to monitor the operational loads, which inevitably increase the weight and system complexity of the aircraft. Therefore, in order to decrease the maintenance costs and data redundancy, the number and location of strain sensors should be optimized for accurate and reliable operational load monitoring. In this paper, a novel two-stage strain gauge location optimization method is proposed to reduce the number of strain gauges while maintaining the operational load monitoring accuracy, which is validated by a numerical case study of an aircraft wing. In the first stage, the traditional Pearson correlation measure is harnessed to initially eliminate numerous correlated strain gauge monitoring points, reducing 996 original strain gauge measurement points to 13 for the aircraft wing box. In the second stage, an improved correlation measure method is proposed to further reduce the 13 strain gauge points to 2, which can evaluate the correlation degree of several variables and simultaneously determine the optimal strain monitoring locations for the two load actuators in this study. The relative errors between the predicted loads and the actual loads for both load actuators are less than 4% when only two optimized monitoring points are adopted. In addition, a comparison study with LASSO regression and principal component regression methods is conducted. The results demonstrate that the proposed method has the characteristics of less monitoring points and higher load prediction precision. Full article

Probability of detection (POD) is an acknowledged mean of evaluation for many investigations aiming at detecting some specific property of a subject of interest. For instance, it has had many applications for Non-Destructive Evaluation (NDE), aimed at identifying defects within structural architectures, and can easily be used for structural health monitoring (SHM) systems, meant as a compact and more integrated evolution of the former technology. In this paper, a probability of detection analysis is performed to estimate the reliability of an SHM system, applied to a wing box composite spar for bonding line quality assessment. Such a system is based on distributed fiber optics deployed on the reference component at specific locations for detecting strains; the attained data are then processed by a proprietary algorithm whose capability was already tested and reported in previous works, even at full-scale level. A finite element (FE) model, previously validated by experimental results, is used to simulate the presence of damage areas, whose effect is to modify strain transfer between adjacent parts. Numerical data are used to verify the capability of the SHM system in revealing the presence of the modeled physical discontinuities with respect to a specific set of loads, running along the beam up to cover its complete extension. The POD is then estimated through the analysis of the collected data sets, wide enough to assess the global SHM system performance. The results of this study eventually aim at improving the current strategies adopted for SHM for bonding analysis by identifying the intimate behavior of the system assessed at the date. The activities herein reported have been carried out within the RESUME project. Full article

The tail wing of box-launched aircraft needs to be folded in the launch box, which can easily cause malfunctions during flight deployment. This article presents a ducted tail wing aircraft that does not require folding of the tail wing. To address the nonlinear problem of lift coefficient in the ducted tail, an aerodynamic optimization method for ducted tails based on the sparrow search algorithm with back-propagation (SSA-BP) neural network approximate model and multi-objective genetic algorithm fusion is proposed, with the goal of improving the lift-to-drag ratio and linearization degree of the lift curve. The linearization degree of the optimized tail lift coefficient curve is significantly improved, and the lift-to-drag ratio is significantly improved under cruising conditions. Based on this optimization result, the shape of the tail wing and fuselage combination was optimized, and the optimal configuration of the ducted tail wing aircraft was selected, providing a reference for the design of ducted tail wing aircraft. Full article

The objective of this paper is to outline a method for the systematic analysis and calculation of the constrained torsional shear stress in corrugated steel web composite box girders. Initially, leveraging Umansky’s secondary theory, the calculation formula for the constrained torsional shear stress within the composite girder is derived from the conditions of cross-sectional torque equilibrium and continuity in warping displacement. Subsequently, a torsion test is conducted using a scaled model of an actual girder. Finally, the constrained torsional shear stress of the corrugated steel web composite girder is examined based on theoretical analyses and the results of torsion testing. The influence of wing plate length and web thickness on the torsional shear stress of the composite girder is also investigated. The findings reveal a strong agreement between the experimental results obtained from model testing and the theoretical calculations. Notably, under torsional constraint, it is observed that the shear stress in the web is maximal and evenly distributed, followed by the bottom plate and then the top plate, with no discernible shear stress observed at the free end of the cantilever plate. Numerical analysis indicates that an increase in the relative width of the cantilever plate initially leads to an increase in shear stress for both the cantilever plate and roof plate, followed by a decrease until reaching a relative width value around 0.6, where the changes tend to stabilize. Moreover, an increase in web thickness results in a monotonic decrease in web shear stress. Additionally, the shear stress of the roof and bottom plate decreases initially before subsequently increasing. Full article