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Highlights The increasing reliance of the aerospace industry on lightweight yet robust materials, notably carbon fiber‐reinforced polymers (CFRPs), has emphasized the need for efficient joining methods for composite structures. This study investigates the influence of various bonding techniques on the strength of two distinct joint configurations: CFRP/CFRP and CFRP/301 steel interfaces. The CFRP/CFRP joints were configured as single lap joints, where two CFRP laminates and/or prepregs were overlapped and bonded using co‐curing, secondary bonding, or co‐bonding. The configuration ensured adhesion between the cured or uncured CFRP layers, depending on the bonding technique applied. For CFRP/301 steel, CFRP laminates and/or prepregs were similarly bonded to 301 steel substrates in an overlapping region. Both configurations were subjected to single lap shear tests following ASTM D3165 standards to assess the mechanical performance of each bonding method. The post‐test interface damage and fracture mechanisms were analyzed using optical microscopy, providing insights into the failure modes for each joint type. This study offers comprehensive experimental data on various joining techniques that can be useful during the initial design phase of aerospace systems, ultimately resulting in cost savings. The findings of this study, when analyzed from an industrial standpoint, indicate that co‐curing offers a promising solution due to its affordability and simplicity, making it especially advantageous for CFRP/301 steel overlap joining when combined with adhesive films. Co‐curing, co‐bonding, and secondary bonding techniques were applied to CFRP/steel joints in real aircraft components. The CFRP/CFRP joints obtained via co‐curing exhibited improved thermal stability and strength. Peel ply surface preparation enhanced adhesion the strength of the CFRP/CFRP bonded samples. Cohesion failure was observed in adhesive joints, with no failure at the bond lines. [ABSTRACT FROM AUTHOR]

CSAM deposition of Ti6Al4V is a challenging task, and high-quality deposits conforming to the AM application standards have not been developed so far. In our study, two distinct feedstock Ti6Al4V powders with different morphology and microstructure were used, and their influence on the key CSAM deposition parameters was investigated. The deposits were analyzed in terms of microstructure (including porosity), electrical conductivity, as well as tensile properties before and after heat treatment. The process gas temperature was found as the most influencing parameter, and the spherical plasma atomized powder resulted in a higher deposit density and electrical conductivity than the crystalline powder at 1100 °C and 50 bars. Using the optimal deposition parameters and heat treatment, unprecedented tensile properties for CSAM Ti6Al6V deposits were achieved, exhibiting 887 MPa yield strength and 929 MPa ultimate tensile strength, values that satisfy the ASTM B381 requirements for Ti6Al4V forgings, and a substantial 4.74% elongation. [ABSTRACT FROM AUTHOR]

This study presents a novel hybrid‐sandwich composite structure, customized for nose radomes applications, incorporating a foam core and distinct opposite face sheets composed of Kevlar and S‐Glass materials. Addressing in‐phase electromagnetic properties, UV protection and low velocity impact responses in our previously published work, this paper empirically and numerically investigates the damage tolerance response of the proposed structures through compression after impact (CAI) testing. The low velocity impacts (LVIs) on S‐Glass face sheets exhibited unique energy dispersion and absorption mechanisms, resulting in variations in indent damage depths and widths across all impact energy levels as compared with LVIs on Kevlar face sheets. After experimentally assessing the CAI behavior, a FE model is developed to predict CAI behavior, which closely aligned with experimental findings. This study, unprecedented in existing literature, proposes hybrid sandwich structures for nose radome aerospace applications, with superior specific impact and residual strength compared to various composite sandwich structures documented in the published literature expanding its utility beyond radomes. Highlights: Innovative composites with superior low velocity impact response, tested for compression after impact performance.Designed for nose radomes found suitable for other impact prone applications.Experimental and numerical modeling showed comparable results.Major differences observed in damage mechanics, resistance, and tolerances. [ABSTRACT FROM AUTHOR]

Real service requirements of the assembly performance and joining properties of design components are critical for composite usage in the aerospace industry. This experimental study offers a novel and comprehensive analysis of dry drilling optimization for glass-reinforced, high-performance epoxy matrix composites used in aerospace structures, focusing on thrust force and delamination. The study presents a first-time investigation into the combined effects of spindle speed (1000, 2250, 4000 and 5750 rpm), feed rate (0.2, 0.4, 0.6 and 0.8 mm/rev) and tool diameter (3 and 5 mm) using a custom-designed drill tool specifically developed for this application, filling a gap in the current literature. By employing the Taguchi design of experiments, the study identified that medium spindle speeds (2250–4000 rpm), lower feed rates (0.2 mm/rev) and smaller tool diameters (3 mm) provided optimal conditions for minimizing thrust force and delamination. These results present actionable insights into improving the structural integrity and performance of drilled aerospace-grade composite components, offering innovative advancements in both the aerospace and defense industries. [ABSTRACT FROM AUTHOR]

In the present research article, the acoustic shock wave-resistant efficiency of silica microparticles (SiO 2 -α-cristobalite)) has been experimentally evaluated in terms of structural, optical and morphological stability against the impact of shock waves. The required SiO 2 particles were synthesized by a hydrothermal method which was subjected to a different number of shock pulses such as 200,400 and 600 with Mach number 2.2. Shocked samples' structural, morphological and optical stabilities have been evaluated by utilizing a powder X-ray diffractometer (PXRD), Ultraviolet–Diffuse reflectance spectrometer (DRS) while the surface morphological analysis has been scrutinized by the field emission scanning electron microscopic technique (FESEM) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy techniques are utilized to evaluate oxidation states and crystallographic structural stability. The above-mentioned analytical techniques provide convincing proofs whereby the synthesized SiO 2 particles are authentically proven to possess outstanding structural, optical and morphological stability against the impact of shock waves. The implicated experimental results and the arguments strongly suggest that the SiO 2 particles are suitable candidates for aerospace and defense industry applications due to their outstanding shock wave-resistant properties. [ABSTRACT FROM AUTHOR]

Usage of thermoplastic composites with low densities is increasing, with lightness coming to the fore especially in the aerospace industry while various sectors like automotive, electronics, sport etc. are also following the trend. Important factors for the preference of thermoplastics are the increase in the amount of waste of conventional materials in addition with increasing product requirements. Composite wastes are accumulated in certain composite collection centers in the world and disposed by incineration. Until at least 2025, studies on recycling are carried out in the European Union. Within this regard, the most important feature of thermoplastics is that they can be melted and shaped again at high temperatures. In this way, recycling of fibers and matrices is possible. Mainly thermal and chemical methods are preferred for obtaining fibers while mechanical methods are preferred for obtaining the matrix. Hence, it is aimed to use both open and closed loop recycling in order to reduce wastes, energy consumption, fossil fuel consumption, and the carbon footprint. Note that these recycling approaches are also of significance for the circular economy concept. Correspondingly, this review thematizes current recycling methods for thermoplastic composites. [ABSTRACT FROM AUTHOR]

A series of experimental and numerical studies were carried out on the mechanical and geometric performance of an aerostructural part produced by a material out-of-autoclave stamp forming process using unidirectional (UD) carbon fiber (CF) reinforced polyetherketoneketone (PEKK), which provides advantages like reshaping, recycling, welding, and low serial manufacturing costs. As a novelty, initial part geometry, different types of springs, and their attachment type were examined experimentally and compared with simulations. Compression tests were performed to determine mechanical strengths which reach levels up to 550 MPa. In addition, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were conducted to determine the crystallinity which occurs depending on the cooling regimes of the material. The crystallinity has been observed to vary regionally ranging from 16 to 21%. However, the crystallinity of the part towards the cold mold region decreased from 20 to 17%. In addition, simulations were performed to observe and control the occurrence of wrinkles and other defects. [ABSTRACT FROM AUTHOR]

Numerical techniques are developed to generate innovative lightweight designs, difficult to obtain with traditional product manufacturing technologies. The use of advanced engineering design software makes it possible to generate un‐conventional geometries, combining a standard density‐based topology optimization approach with lattice structure‐based methods. Deep knowledge of modeling aspects is required to improve the topology optimization processes currently performed in aerospace applications, as well as to achieve design solutions suitably prepared for additive manufacturing technologies. In the present work, algorithms based on solid isotropic material with penalization (SIMP) method are used to reduce the weight of parts by removing unnecessary material from the initial part design. Moreover, the integration of lattice structures in the topology optimization procedures allows for a further part weight reduction offering the possibility of exploiting the potentials of 3D printing in the fabrication of complex geometries. [ABSTRACT FROM AUTHOR]

The aerospace industry has progressively grown its use of composites. Electrically conductive nanocomposites are among important modern materials for this sector. We report on a bulk composite containing silver nanowires (AgNW) and an aerospace grade epoxy for use in carbon fiber reinforced polymers (CFRPs). AgNWs' surfaces were also modified to enhance their ability to be dispersed in epoxy. Composites were obtained by use of three-roll milling which is of major interest for industrial applications, especially for the aerospace sector, since the process is scalable and works for aerospace grade resins with high curing temperatures. Our main objective is to improve the electromagnetic interference (EMI) shielding performance of CFRPs via improving the properties of the resin material. The addition of AgNWs did not considerably alter the flexural strength of the epoxy, however the composite with surface-modified AgNWs has a 46 % higher flexural strength. Adding AgNWs over a low threshold concentration of 0.05 wt% significantly enhanced the electrical conductivity. Conductivities above the percolation threshold lie around 102 S/m. At a concentration of 5 wt% AgNW, the EMI shielding efficiency (SE) of epoxy increased from 3.49 to 12.31 dB. Moreover, the thermal stability of the epoxy was unaffected by AgNWs. As a result, it was discovered that (surface modified) AgNWs improved the (multifunctional) capabilities of the aerospace grade epoxy resin which might be used in CFRPs to further enhance properties of composites parts, demonstrating suitability of AgNWs' as a reinforcement material in aerospace applications. [ABSTRACT FROM AUTHOR]

The thermal conductivity coefficient of epoxy composites for aircraft, which are reinforced with glass fiber and filled with aerosil, γ-aminopropylaerosil, aluminum oxide, chromium oxide, respectively, was simulated. To this end, various machine learning methods were used, in particular, neural networks and boosted trees. The results obtained were found to be in good agreement with the experimental data. In particular, the correlation coefficient in the test sample was 0.99%. The prediction error of neural networks in the test samples was 0.5; 0.3; 0.2%, while that of boosted trees was 1.5; 0.9%. [ABSTRACT FROM AUTHOR]

Delamination due to an inferior adhesion between reinforcement material and matrix in carbon fiber-reinforced thermoplastic (CFRTP) composites is a crucial problem to be solved. To this end, this study aims to overcome poor wettability between reinforcing phase, i.e., carbon fiber (CF), and thermoplastic matrix, i.e., polyetherether ketone (PEEK). Herein, CF's surface was tailored by application of different polymeric sizing agents which have different chemical structures. Morphology and topology analyses were performed by Scanning Electron Microscope and 3D laser scanning, respectively. Later, a variety of wettability results were obtained by the sessile drop method used in Contact Angle (CA) measurements for CFs throughout application of each sizing agent applied by dip coating. Sizing materials were designed such that the chemical structure of CF's surface could exhibit compatibility with the matrix itself. Consequently, complete wettability (CA: 0°) was achieved for CFs sized by HPEEK (CF/hydroxylated PEEK (HPEEK)) and the surface free energy (SFE) of CF was enhanced from 5.43 to 72.8 mJ/m2 while the SFE of the PEEK matrix is 40.1 mJ/m2. Moreover, sizing by HPEEK improved the average surface roughness of CF by 32% which enables optimized adhesion. Afterward, repetitive tensile tests were carried out to observe effects of improved interfacial interlocking on the mechanical properties of the final CFRTP composite. Stress–strain curves revealed that the tensile strength of CFRTP improved from 473 to 508 MPa through the sizing of CF by HPEEK whereas pristine PEEK has a much smaller tensile strength (98 MPa) than the aforementioned CF-reinforced composites. The sizing of carbon fiber's surface by HPEEK resulted in an enhanced adhesion with the PEEK matrix. Since the chemical structure and physical properties of sizing agent and matrix are compatible, potential debonding between them was eliminated. Thus, the improved wettability led to a substantial increase in the mechanical strength of the final TP composite. [ABSTRACT FROM AUTHOR]

Glare (Glass Reinforced Aluminium) which consists of fibre metal laminate composite consisting of aluminium and glass is used aerospace structures are supposed to buckling and impact loads. Lateral buckling analyses were made to determine critical buckling loads, and results were compared to Al 2024-T3 in this paper. Weight and load carrying capacity of Glare grades were taken into consideration and the importance of weight to critical load was stated. Numerical works were carried out by starting with Glass and Aluminum then continued for Glare Grades of Glare 2A, Glare 2B, Glare 3A, Glare 3B, Glare 4A, Glare 4B, Glare 5A, Glare 5B, Glare 6A and Glare 6B to estimate buckling load values. Several comparisons were presented for Glare grades based on Al 2024-T3 through paper. Glare 2A, 2B, 3A, 3B, 6A and 6B Grades have lower weight and buckling load values compared to Al 2024-T3. Lower weight is essential for aerospace applications. But optimum weight and load carrying capacity can be selected for intended applications by taking weight and load into consideration at same time. Although Glare grades of 4A 2-1, 4B 2-1, 5A 2-1 and 5B 2-1 having closer weight (17.60g, 17.60g, 19.13g and 19.13g respectively) to Al 2024-T3 (17.31g), higher buckling loads were determined for Glare grades numerically. The best choice for Glare as an alternative to Al 2024- T3 under lateral buckling loading can be decided for point of views of less weight to critical load ratio. [ABSTRACT FROM AUTHOR]

This review critically examines recent advancements in carbon nanotube (CNT) polymer composites, focusing on innovative synthesis, functionalization, and fabrication strategies that enhance their mechanical, thermal, and electrical properties. Special emphasis is placed on their applications in aerospace and automotive industries, where these composites have demonstrated the potential to achieve weight reductions of up to 40% and fuel efficiency improvements of 20–25%. This work identifies key challenges, such as achieving uniform CNT dispersion and robust interfacial bonding, while addressing scalability issues in large-scale production. Comparative evaluations with traditional materials underscore the environmental and performance benefits of CNT composites. A comprehensive analysis of advanced fabrication techniques, along with a detailed summary table, provides technical insights and outlines pathways for future research and industrial implementation. This review aims to guide the development of next-generation lightweight, high-performance materials for critical engineering applications. • Ultra-high strength CNT composites for aerospace and automotive industries. • Weight reductions of up to 40% with a 20–25% increase in fuel efficiency. • Advanced CNT functionalization and dispersion techniques explored. • Real-world case studies demonstrate improvements in performance and sustainability. [ABSTRACT FROM AUTHOR]

Thermoplastic composites outperform in aerospace applications compared to thermoset composites due to their weldability, a key advantage. This feature streamlines manufacturing, allowing for precise assembly of complex shapes, reducing costs, and accelerating production. Additionally, it simplifies maintenance, enabling easy repair or replacement of damaged parts, thereby extending vehicle lifespan and minimizing downtime. With exceptional strength-to-weight ratio and resistance to corrosion and fatigue, weldable thermoplastic composites ensure reliable performance in the demanding aerospace environment. Overall, their weldability enhances efficiency, versatility, and safety in aerospace applications. This paper first presents an overview of various welding processes and discusses the special challenges of assembly processes in the aviation industry. This work then focuses from the authors' perspective with regard to industrializability on the two most promising processes, resistance and ultrasonic welding. [ABSTRACT FROM AUTHOR]

Aerospace composite materials’ performance and application level are vital symbols for measuring the advancement and dependability of aerospace models, and they are the key materials enabling the development of aerospace models, which define the performance and success of models. This review summarizes recent significant research advances in the fields of thermal structure, heat protection, thermal wave transmission, heat insulation, and structural composite materials, and proposes new materials for extreme environments, reusable anti-thermal insulation materials, third-generation structural composite materials, and new materials for extreme environments. Low-cost and quick composite component manufacturing is an essential avenue for the future development of aerospace composite materials. [ABSTRACT FROM AUTHOR]

DC-Excited vernier reluctance machine (DC-VRM) using a 12-slot/10-pole-pair design, exhibits the advantages of small torque ripple and low cogging torque due to the inherent commentary characteristic. However, the inherent saliency is canceled out by a 12/10 pole combination of machine design driven by a traditional three-phase inverter. As a result, the sensorless operation in zero/low-speed regions becomes difficult because the position estimation methods using self-inductance detection cannot be applied. To tackle this problem, we first analyzed the saliency annihilation phenomenon through Fourier analysis that the odd-order harmonics in self-inductance are canceled. Moreover, reconstructing saliency method is proposed by splitting a phase winding into two sub-phase coils and using parallel H-bridge converters to supply sub-phase coils and achieve sensorless drive. Through this method, the saliency effect is recovered in self-inductance, thereby pulse injection sensorless drive can be applied. The constructed 12/10 DC-VRM sensorless drive shows good fault-tolerant ability and can be applied in safety-critical industry applications such as aerospace propulsion. Analysis and experiments are performed in the initial position detection, start-up and free-running stages to verify the feasibility of the proposed solution. A sector estimation accurate to 6° can be achieved. [ABSTRACT FROM AUTHOR]

Active camber morphing technology can be used to improve aircraft performance in takeoff and landing flight conditions, while preserving a smooth wing shape. This study begins with the design of a morphing droop nose to be installed on a regional aircraft, and focuses on the manufacturing and testing of a full-scale and fully representative experimental prototype. All work is driven by the morphing shape change, which was optimized to provide the required aerodynamic performance. The adoption of a composite structure that combines a flexible skin with a compliant structure makes this device capable of achieving such a shape change, and sufficiently insensitive to external load variations. These capabilities are successfully demonstrated through experimental testing. A validation phase was conducted based on strain gauge measurements, and a motion capture system was used to identify three-dimensional shape changes due to the morphing. Finally, a validated numerical model is used to assess the aerodynamic performance of the experimental prototype. [ABSTRACT FROM AUTHOR]

The paper provides a description of the design, finite-element analysis, and testing of two optimized composite profiles intended primarily for joining aircraft structures. Profiles with T and Y shapes were manufactured using the thermoforming technology by a one-shot process from a C/PPS (carbon fibers and a polyphenylene sulfide matrix fabric). Such profiles are usually loaded in the pull direction. A finite-element analysis was performed to provide that these profiles are able to withstand the prescribed ultimate load without causing their damage. Static and fatigue tests were conducted on both profiles to determine their strength and construction limits, and results similar to those from FE simulations were found, i.e., both the profiles could withstand the prescribed load without degradation. [ABSTRACT FROM AUTHOR]

In this study, the kinetic parameters belonging to the cross-linking process of a modified epoxy resin, Aerotuf 275-34™, were investigated. Resin curing kinetics are crucial to understanding the structure–property–processing relationship for manufacturing high-performance carbon-fiber-reinforced polymer composites (CFRPCs). The parameters were obtained using differential scanning calorimetry (DSC) measurements and the Flynn–Wall–Ozawa, Kissinger, Borchardt–Daniels, and Friedman approaches. The DSC thermograms show two exothermic peaks that were deconvoluted as two separate reactions that follow autocatalytic models. Furthermore, the mechanical properties of produced carbon fiber/Aerotuf 275-34™ laminates using thermosetting polymers such as epoxies, phenolics, and cyanate esters were evaluated as a function of the conversion degree, and a close correlation was found between the degree of curing and the ultimate tensile strength (UTS). We found that when the composite material is cured at 160 °C for 15 min, it reaches a conversion degree of 0.97 and a UTS value that accounts for 95% of the maximum value obtained at 200 °C (180 MPa). Thus, the application of such processing conditions could be enough to achieve good mechanical properties of the composite laminates. These results suggest the possibility for the development of strategies towards manufacturing high-performance materials based on the modified epoxy resin (Aerotuf 275-34™) through the curing process. [ABSTRACT FROM AUTHOR]

The use of lighter materials is one of the efficient means to mitigate the increasing demands on fuel resources, reduce CO2 emissions. Mg is one of the lightest material available and possesses exciting range of properties such as low density and high strength to weight ratio. Despite such exciting properties, the applications of Mg and its alloys were very limited in aerospace, automotive, and biomedical industries but recently the application is picking-up. The restricted application is attributed to anisotropy, poor corrosive resistance, and inflammability of Mg. The current review addresses the barriers limiting the widespread application of Mg based materials. Furthermore, the mitigation of the problems of anisotropy, poor corrosion resistance, ductility, and inflammability of Mg are critically reviewed. The findings of this research provide insights of the processing techniques, properties and how to address the potential barriers of limited applications. The review paper will assist and motivate the researchers to ponder and overcome numerous problems related to Mg and its alloys by understanding the importance of each problem discussed in this review. An attempt has also been made to arrange research status on issues and the mitigation thereof with respect to Mg and its alloys as single reference point. [ABSTRACT FROM AUTHOR]

In the present research article, authors have experimentally evaluated the shock wave resistant properties of technologically potential materials of the anatase and the rutile phase TiO2 nanoparticles at the dynamic shock wave loaded conditions. The shock wave resistant behavior has been quantitatively drawn utilizing the crystallographic phase stability of the test samples for which the required crystallographic information has been extracted from the powder XRD patterns. Based on our observed experimental results as well as the respective interpretations, it is strongly authenticated that Rutile TiO2 NPs are suitable candidates for aerospace and defense industrial applications of materials fabrications because of the outstanding shock resistant properties than that of Anatase TiO2 NPs which undergo the crystallographic phase transition of rutile-TiO2 at shocked conditions. [ABSTRACT FROM AUTHOR]

Lattice structures, produced by repeated unit cells in the particular pattern, offer a high strength-to-weight ratio. The current advancement in Additive manufacturing (AM) technology, creating complex geometries like lattice structures has revolutionized production across various industries. While several reviews have focused on different specific aspects of lattice structures, a comprehensive overview of recent advancements of lattice in aerospace structural applications is lacking. Therefore, a comprehensive review of lattice structures used in aerospace lightweight applications manufactured through AM is presented here. Basic classification of lattice structure is presented followed by detailed study of several factors influencing mechanical properties of lattice structures, crucial for aerospace lightweight application. Current trends in manufacturing technologies of lattice structures are analyzed in detail with identification of capabilities and limitations. Furthermore, detailed literature on the lattice structure optimization techniques is presented with current limitations. Furthermore, the engineering applications of lattice structures in aerospace lightweight, along with the fabrication processes involved, challenges in applications of lattice in aerospace applications and future research directions are reported. By providing insights into current research trends and future directions, this review serves as a valuable resource for researchers and engineers involved in the design and development of lightweight aerospace lattice structures. It lays the groundwork for the exploration of new and innovative lattice structures tailored to meet the evolving needs of the aerospace industry. [ABSTRACT FROM AUTHOR]

• The GWP of PSC module with carbon electrode is calculated to be 3.0 g/m2 and 12 g/kWh. • Gold dominates cost and environmental impacts of PSC devices fabricated from both screen coating and R2R slot-die. • The cost is reduced more than 50% by replacing gold electrode with carbon electrode. • Sprio-OMeTAD as hole transport layer has highest cost of PSC with carbon electrode. In the past few years, we have witnessed a rapid evolution of perovskite solar cells. In this study, we employ life cycle assessment (LCA) to identify the potential environmental impacts of perovskite solar cells (PSC) optimised for aerospace applications but could be used in conventional terrestrial applications too. One PSC module is manufactured by spin coating equipped with ITO glass and gold cathode. The other PSC module is manufactured by slot-die coating with a PET layer and carbon cathode and gold cathode respectively. Life cycle assessment is employed to compare potential environmental impact of two manufacture methods by impact method of Recipe(H), as well as the fabrication cost of PSC module. The primary data of material and energy used for fabricating PSCs are collected from spin coating with lab scale and slot-die coating with pilot scale. The life cycle impact assessment of the PSC module in the pilot scale shows much lower in all the assessed 18 impact categories than in the lab scale thanks to the material use efficiency and reducing energy consumption. Gold as a conduct electrode has the highest impacts in both spin coating and slot-die coating modules. Calculating with a two-year lifetime (typical of aerospace applications), the impact of global warming potential from the PSC module with carbon electrode with pilot scale used in a terrestrial application is calculated to be 12 g/kWh. [ABSTRACT FROM AUTHOR]

As a result of the widespread use of composite materials in primary structures of aerospace platforms, composite joining became more crucial. This study addresses the effect of joining methods on the strength of composite joints experimentally, numerically and analytically. Single lap joint shear strengths of carbon fiber reinforced epoxy composite parts joined by mechanical fastening with a pop and solid rivet, secondary bonding with a paste adhesive, co-curing and co-bonding techniques were compared. In addition, the effect of adhesive thicknesses (0.2, 0.4, 0.6, 0.76 mm) on the single lap shear strength was investigated. Carbon fiber reinforced composite (CFRP) samples were produced according to the ASTM 5868 standard. After the production of samples with varying joining methods, single lap shear tests were implemented. Moreover, the interface damage in the composites was examined by use of a scanning electron microscope (SEM) for the purpose of studying the damage mechanism. Fracture mechanisms corresponding with bonding methods were also assessed by examining the fracture surface of the composite samples. Furthermore, results were analyzed by Hypermesh, ABAQUS and ESAComp. For instance, the co-bonded sample with an adhesive film exhibits an experimental shear strength of 24.03 MPa which deviates only 3 % from the numerical expectation. [ABSTRACT FROM AUTHOR]

For safety‐critical applications, electrical machines need to satisfy several constraints, in order to be considered fault tolerant. In fact, if specific design choices and appropriate control strategies are embraced, fault‐tolerant machines can operate safely even in faulty conditions. However, particular care should be taken for avoiding uncontrolled thermal overload, which can either cause severe failures or simply shorten the machine lifetime. This study describes the thermal modelling of two permanent magnet synchronous machines for aerospace applications. In terms of the winding's layout, both machines employ concentrated windings at alternated teeth, with the purpose of accomplishing fault‐tolerance features. The first machine (i.e. Machine A) adopts a three‐phase winding configuration, while a double three‐phase configuration is used by the second one (i.e. Machine B). For both machines, the winding temperatures are evaluated via simplified thermal models, which were experimentally validated. Copper and iron losses, necessary for the thermal simulations, are calculated analytically and through electromagnetic finite‐element analysis, respectively. Finally, two aerospace study cases are presented, and the machines' thermal behaviour is analysed during both healthy and faulty conditions. Single‐phase open‐circuit and three‐phase short‐circuit are accounted for Machines A and B, respectively. [ABSTRACT FROM AUTHOR]

Bistable laminates have attracted considerable interest among researchers as prospective candidates for delivering exceptional performance within the domain of morphing structures. These laminates exhibit a distinctive characteristic of featuring two stable states, sustaining their configuration until the application of a critical force that triggers a transition to their second stable position. Before discussing the practical applications involving bistable composite laminates, this paper presents analytical modeling for predicting the room-temperature shape and simulating the snap-through phenomena. The main aspects of the room-temperature shape simulation are discussed, and various snap-through triggering methods are shown. At this point, the paper focuses on a comparative analysis of numerical predictions in contrast to experimental data aimed at discerning the reliability of existing models. Furthermore, this paper not only elucidates existing challenges but also delineates potential avenues for future research. As the investigation into bistable composites progresses from comprehending intrinsic phenomena to practical, real-world applications, this study outlines both the present and potential future research concerning bistable composite laminates. [ABSTRACT FROM AUTHOR]

Polyimide (PI)-silica aerogel composite aerogels with low shrinkage (3.7%), low density (0.061 g/cm3), low thermal conductivity (0.0216 W m−1 K−1), high hydrophobicity (146°) and good fire resistance were prepared by incorporating silica aerogel powders into PI matrix. The properties of the aerogels are affected by the type and content of silica aerogel powders. The samples show high compressibility, and the stress at 80% strain increases with the increase of silica aerogel powder content. The addition of inorganic silica aerogel powders (ISAp) can improve the thermal stability of the aerogel and the fire resistance and structural integrity of the sample under flame, but has adverse effect on moisture resistance. While the addition of polyvinylpolymethylsiloxane aerogel powders (PAp) improves the moisture resistance of the aerogel but weakens the thermal stability and fire resistance. The introduction of both ISAp and PAp can reduce the thermal conductivity of the aerogel, and the samples exhibit good thermal insulation performance. Furthermore, ground equivalent simulation tests were carried out to verify the adaptability of these aerogels in the space environment. The sample meets the standard requirements and shows stable structure and performance during the tests, which proves its potential application in the aerospace field. [Display omitted] • Reduced shrinkage and increased hydrophobicity of PI aerogel were achieved by using two diamines simultaneously. • Physically mixing of silica aerogel powders into PI matrix reduces the shrinkage and thermal conductivity of PI aerogel. • The adaptability of PI aerogel in space environment was verified by ground equivalent simulation tests. [ABSTRACT FROM AUTHOR]

Abstract Cylindrical lattice structures are types of lightweight structures and can utilize the orthotropy of fiber-reinforced composite materials. Maximization of the buckling loads is important because they dominate the strength of the structures. On the basis of the fact that a hyperboloidal shape deviation increases the buckling loads of cylindrical homogeneous shells, the changes in the buckling loads of cylindrical lattice structures with a hyperboloidal shape deviation are discussed. Further, the buckling loads of both conventional cylindrical lattice structures and shape-deviated hyperboloidal lattice structures with respect to the compressive, bending, and torsional loads are calculated using a finite element method. The results show that the shape deviation decreases the buckling loads, while the change in mass is negligible. The effects of the shape deviation on the buckling loads differ between homogeneous shell structures and lattice structures. [ABSTRACT FROM AUTHOR]

This study presents an optimisation method for slotless permanent magnet synchronous machines to maximise torque density. The slotless structure with outer rotor and Halbach array has been selected to limit iron losses, torque ripple, cogging torque, and high‐order harmonics. High‐speed operation compounds both ac copper loss and mechanical stress. The former causes a temperature rise in the machine, while the latter is induced by strong centrifugal forces. A finite‐element analysis‐based optimisation method that utilises a parallel multistart, mesh adaptive direct search strategy is proposed to consider ac copper loss and mechanical stress as constraint variables. Finally, the torque densities of titanium and aermet shell designs were compared to show how material selection provides a trade‐off in terms of torque production, mechanical stress, and weight. [ABSTRACT FROM AUTHOR]

IR pulsed laser radiation in air was applied to Si 3 N 4 and Invar to obtain reliable Si 3 N 4 /Si 3 N 4 and Si 3 N 4 /Invar adhesive bonded components. The laser pre-treatment produced a homogeneous nanostructured oxide layer on the surfaces, which effectively increased the adhesion at the adhesive/adherends interface and led to cohesive failure in the joining material. The mechanical strength of Si 3 N 4 / Si 3 N 4 and Si 3 N 4 /Invar joined components was measured, with and without laser nanostructuring, before and after thermal cycling from room temperature to 50 K, and it resulted that the exposure to extremely low temperatures did not affect the mechanical integrity of the joints. It was also demonstrated that this laser pre-treatment did not alter the mechanical properties of the ceramic substrate. [ABSTRACT FROM AUTHOR]

In this paper a new “active output filter” (AOF) for variable speed constant frequency (VSCF) power system in aerospace applications is proposed. The proposed AOF is envisioned as a power semiconductor filter block. In the proposed system the passive L-C output filter components are replaced by an H-bridge. The H-bridge is operated at high frequency to inject voltage harmonics to achieve a sinusoidal output voltage to the load. Advanced wide band gap devices can be employed in the design of AOF block to obtain high performance with simultaneous reduction in size. The proposed AOF concept offers a significant reduction in size/weight compared to passive L-C. Further, in the presence of AOF the main VSCF inverter can be operated in a six-step and/or at a reduced PWM frequency. An example 250 kVA, 3-phase 400-Hz system with the proposed AOF concept is evaluated via simulation with a corresponding passive L-C filter configuration. Experimental results on reduced kVA laboratory prototype are discussed. [ABSTRACT FROM AUTHOR]

A novel recognition of ellipses and relative pose estimation algorithm is presented based on surface of revolution (SOR) in this paper for images of multiple ellipses. Firstly, the contours following method is performed on image to detect ellipses. Secondly, candidate ellipses projected by circular cross section of a SOR are obtained based on parallel constraint and vertical constraint in the image. Finally, relative pose between target and camera is calculated by these candidate ellipses. Experimental results indicate that the method perform well in recognition and estimation. The precision of recognition is higher than 97% for synthetic images corrupted by 0 ∼ 16% salt-and-pepper noise. The absolute error of pose angle is 1°,and the absolute error in axis z and other axis are less than 80 mm and 15 mm, respectively, when measure distance is less than 10 m. [ABSTRACT FROM AUTHOR]

The paper treats a class of optimal control problems for deterministic nonlinear discrete-time systems with the objective of maximizing the time or total yield until prescribed constraints are violated. Such problems are referred to as drift counteraction optimal control (DCOC) problems as the corresponding control policy may be viewed as optimally counteracting drift imposed by disturbances or system dynamics. We derive conditions for the existence of an optimal solution. The optimal control policy is characterized by the value function and a new algorithm based on proportional feedback is presented that obtains the value function faster than conventional dynamic programming algorithms. In addition, an approximate dynamic programming (ADP) approach using Gaussian process regression is formulated based on the new algorithm. Two numerical examples are reported, a time maximization problem for a van der Pol oscillator and a satellite life extension problem. [ABSTRACT FROM AUTHOR]

One of the earliest approaches in gain-scheduling control is the gridding based approach, in which a set of local linear time-invariant models are obtained at various gridded points corresponding to the varying parameters within the flight envelop. In order to ensure smooth and effective Linear Parameter-Varying control, aligning all the flexible modes within each local model and maintaining small number of representative local models over the gridded parameter space are crucial. In addition, since the flexible structural models tend to have large dimensions, a tractable model reduction process is necessary. In this paper, the notion of σ -shifted H 2 - and H ∞ -norm are introduced and used as a metric to measure the model mismatch. A new modal alignment algorithm is developed which utilizes the defined metric for aligning all the local models over the entire gridded parameter space. Furthermore, an Adaptive Grid Step Size Determination algorithm is developed to minimize the number of local models required to represent the gridded parameter space. For model reduction, we propose to utilize the concept of Composite Modal Cost Analysis, through which the collective contribution of each flexible mode is computed and ranked. Therefore, a reduced-order model is constructed by retaining only those modes with significant contribution. The NASA Generic Transport Model operating at various flight speeds is studied for verification purpose, and the analysis and simulation results demonstrate the effectiveness of the proposed modeling approach. [ABSTRACT FROM AUTHOR]

Dispersion and distribution of graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) in polymer matrices without the use of any functionalization and application of conventional procedures such as mixing or sonication does not display the full potential of the fillers due to agglomeration which limits the use of the corresponding nanomaterials. Contrarily, varying GNP and CNT based fillers were integrated to an aerospace grade epoxy resin, which has a high curing temperature of 180 °C and is commonly used as matrix to manufacture structural parts, by use of three-roll milling in this study. This procedure is of major interest for industrial applications, especially for the aerospace sector, since the process is scalable and works for resins with high curing temperatures. Microstructure and thermal properties of the nanocomposites were investigated. Moreover, mechanical and electrical performances were studied. Results show that certain fillers yield multifunctional properties, i.e. enhanced flexural strength up to 64 ± 41 % in combination with low electrical resistivity with orders of magnitude of ∼ 10 − 1 − 10 − 2 Ω m in comparison to the electrical resistivity of the epoxy being 10 9 Ω m. [Display omitted] • Aerospace grade epoxy was reinforced with various carbonaceous fillers. • Electrical conductivity was increased 10 10 fold. • Flexural strength was increased by 64 %. • Industrial methodology compatible with standard manufacturing methods. • Aerostructure which carries static loads was manufactured by this approach. [ABSTRACT FROM AUTHOR]

Adaptive controllers with closed loop reference models have guaranteed transient performance due to the additional design freedom available in them. However, robustness in the presence of both matched perturbations and time delay is not guaranteed, which is a necessary requirement for most of the safety‐critical systems, such as, aerospace applications. This study attempts to achieve guaranteed transient and steady state performance with improved robustness in the presence of both matched perturbations and input delay by incorporating a proportional–integral (PI) compensator in the feedback loop of the closed loop reference model reference adaptive control (MRAC) architecture. The proposed system also reduces high frequency oscillations in control channel without disturbing the relative order of plant. The parameters of PI compensator have been tuned using genetic algorithm. Effectiveness of the proposed work has been validated on standard numerical examples using simulation results and the performance has been compared with similar and recent works. [ABSTRACT FROM AUTHOR]

With increased need for high power density, high efficiency and high temperature capabilities in aerospace and automotive applications, integrated motor drives (IMD) offers a potential solution. However, close physical integration of the converter and the machine may also lead to an increase in components temperature. This requires careful mechanical, structural and thermal analysis; and design of the IMD system. This study reviews existing IMD technologies and their thermal effects on the IMD system. The effects of the power electronics position on the IMD system and its respective thermal management concepts are also investigated. The challenges faced in designing and manufacturing of an IMD along with the mechanical and structural impacts of close physical integration is also discussed and potential solutions are provided. Potential converter topologies for an IMD like the matrix converter, two‐level bridge, three‐level neutral point clamped and multiphase full bridge converters are also reviewed. Wide band gap devices like silicon carbide and gallium nitride and their packaging in power modules for IMDs are also discussed. Power modules components and packaging technologies are also presented. [ABSTRACT FROM AUTHOR]

ARM processors are leaders in embedded systems, delivering high-performance computing, power efficiency, and reduced cost. For this reason, there is a relevant interest for its use in the aerospace industry. However, the use of sub-micron technologies has increased the sensitivity to radiation-induced transient faults. Thus, the mitigation of soft errors has become a major concern. Software-Implemented Hardware Fault Tolerance (SIHFT) techniques are a low-cost way to protect processors against soft errors. On the other hand, they cause high overheads in the execution time and memory, which consequently increase the energy consumption. In this work, we implement a set of software techniques based on different redundancy and checking rules. Furthermore, a low-overhead technique to protect the program execution flow is included. Tests are performed using the ARM Cortex-A9 processor. Simulated fault injection campaigns and radiation test with heavy ions have been performed. Results evaluate the trade-offs among fault detection, execution time, and memory footprint. They show significant improvements of the overheads when compared to previously reported techniques. [ABSTRACT FROM PUBLISHER]

An effective model of single- and multilayered thin panels, including those formed using carbon fiber composite (CFC) materials, is incorporated into the transmission line modeling (TLM) method. The thin-panel model is a one-dimensional (1-D) one based on analytical expansions of cotangent and cosecant functions that are used to describe the admittance matrix in the frequency domain; these are then converted into the time domain by using digital filter theory and an inverse Z transform. The model, which is extended to allow for material anisotropy, is executed within 1-D TLM codes. And, for the first time, the two-dimensional (2-D) thin-surface model is embedded in unstructured three-dimensional (3-D) TLM codes. The approach is validated by using it to study some canonical structures with analytic solutions, and against results taken from the literature. It is then used to investigate shielding effectiveness of CFC materials in a practical curved aerospace-related structure. [ABSTRACT FROM AUTHOR]

• High-quality Inconel 718-Aluminium parts with no defects, such as pores or cracks. • Good metallurgical bonding with no significant diffusion of elements (5 µm thickness) • Inconel 718-Aluminium specimens display a lower density than the Inc718 bulk (<13 %) • Thermal conductivity Inconel 718-Aluminium was 1.87 times higher than Inconel 718 bulk. In this study, the combination of Inconel 718 (IN718) alloy, widely used in aerospace applications, and a highly conductive low-density Aluminium (Al) was hypothesized to achieve a disruptive solution with improved thermal conductivity and significantly lower weight, key aspects of aerospace industry. A multi-material IN718 – Al solution was designed and later fabricated by combining laser surface texturing and hot-pressing techniques. The multi-material IN718 – Al specimens were produced without significant defects and exhibited a significantly lower density than the IN718 bulk (<13 %), contributing to a weight decrease which can be considered strongly beneficial for improving energy efficiency of aerospace components. The Vickers' microhardness measurements were coherent results with literature and the interface between the two dissimilar materials exhibited a good metallurgical bonding with no significant diffusion of elements. The thermal conductivity of the multi-material IN718 – Al solution was 1.87 times higher than that of IN718 bulk. Multi-material IN718 – Al specimens have shown a high potential to decrease weight and enhance the thermal efficiency of an aerospace component. [ABSTRACT FROM AUTHOR]

This paper deals with a shaft-line-embedded multiphase electrical machine to be connected to the high-pressure shaft of an open-rotor jet engine. An asymmetrical six-phase induction machine (IM) is proposed for this application. The main focus of this paper is on the control of the six-phase IM, to verify its overload capabilities and postfault operations. The implemented control uses a direct-flux vector control scheme based on a double-stator approach, where each three-phase winding set is independently controlled. This way, the fault-tolerant behavior of the drive system is enhanced. Complete details of the adopted flux observer are included; torque and speed control loops are implemented in a dedicated multiple three-phase drive, and a scaled prototype (10 kW, 6000 r/min) has been tested. The overload capability has been verified both in generation and motoring mode, for different speeds and torque up to 150% of the rated one. Finally, the transitions between healthy and faulty modes are reported for open phases and encoder faults. The obtained results demonstrate the feasibility of the proposed drive solutions. [ABSTRACT FROM AUTHOR]

In this paper, we address the problem of designing a control law based on sensor measurements that provides global asymptotic stabilization to a reference trajectory defined on the SE.3/ R6. The proposed control law is a function of the angular velocity, of vector measurements characterizing the position of some given landmarks, and of their rate of change. We provide sufficient conditions for the existence of synergistic potential functions on SO.3/ which are pivotal in the generation of a suitable hybrid control law. We also provide sufficient conditions on the geometry of the landmarks to solve the given problem. Finally, the proposed solution is simulated and compared with a continuous feedback control law. [ABSTRACT FROM AUTHOR]

Software-based techniques offer several advantages to increase the reliability of processor-based systems at very low cost, but they cause performance degradation and an increase of the code size. To meet constraints in performance and memory, we propose SETA, a new control-flow software-only technique that uses assertions to detect errors affecting the program flow. SETA is an independent technique, but it was conceived to work together with previously proposed data-flow techniques that aim at reducing performance and memory overheads. Thus, SETA is combined with such data-flow techniques and submitted to a fault injection campaign. Simulation and neutron induced SEE tests show high fault coverage at performance and memory overheads inferior to the state-of-the-art. [ABSTRACT FROM PUBLISHER]

This paper presents a new X-ray backscatter technique (XBT) for non-destructive imaging of aerospace materials with only a single-sided access. It uses a special twisted slit collimator to inspect the whole object by changing the viewing direction of the X-ray backscatter camera. For the first time, the X-ray backscatter measurements were conducted using high-energy (>500 keV) X-ray sources. Experiments were performed on thick complex structured aluminium components, stringers and honeycomb structures to validate the applicability of the present technique to image small changes in the material properties and also to detect low-density material inclusions. In order to reduce the inspection time from hours to several seconds and to improve the image quality of the X-ray backscatter image, the backscattered signals were measured using a digital detector array with high spatial resolution (200 µm). The influence of the energy of the X-ray source and the slit width of the camera on the X-ray backscatter image were also investigated. In the proposed technique, the whole object is irradiated by an un-collimated X-ray beam resulting in a low image acquisition time of 3 min that facilitates the use of XBT for the real time NDT&E of aerospace materials. [ABSTRACT FROM AUTHOR]