Search Results (1,714)

The natural frequencies and damping characterisation of a new aerospace grade composite material were investigated using a modified impulse method combined with the half power bandwidth method, which is applicable to the structures with a low damping. The composite material of interest was unidirectional carbon fibre reinforced plastic. The tests were carried out with three identical square 4.6 mm thick plates consisting of 24 plies. The composite plates were clamped along one edge in a SignalForce shaker, which applied a sinusoidal signal generated by the signal conditioner exiting the bending modes of the plates. Laser vibrometer measurements were taken at three points on the free end so that different vibrational modes could be obtained: one measurement was taken on the longitudinal symmetry plane with the other two 35 mm on either side of the symmetry plane. The acceleration of the clamp was also recorded and integrated twice to calculate its displacement, which was then subtracted from the free end displacement. Two material orientations were tested, and the first four natural frequencies were obtained in the test. Damping was determined by the half-power bandwidth method. A linear relationship between the loss factors and frequency was observed for the first two modes but not for the other two modes, which may be related to the coupling of the modes of the plate and the shaker. The experiment was also modelled by using the Finite Element Method (FEM) and implicit solver of LS Dyna, where the simulation results for the first two modes were within 15% of the experimental results. The novelty of this paper lies in the presentation of new experimental data for the natural frequencies and damping coefficients of a newly developed composite material intended for the vibration analysis of rotating components. Full article

This work presents the structural analysis and validation of a sub-250 g FPV drone chassis, emphasizing both theoretical rigor and practical applicability. The novelty of this contribution lies in four complementary aspects. First, the structural philosophy introduces a screwless frame with interchangeable arms, joined through interlocking mechanisms inspired by traditional Japanese joinery. This approach mitigates stress concentrations, reduces weight by eliminating fasteners, and enables rapid arm replacement in the field. Second, validation relies on nonlinear static and transient FEM simulations, explicitly including crash scenarios at 5 m/s, systematically cross-checked with bench tests and instrumented flight trials. Third, unlike most structural studies, the framework integrates firmware (Betaflight), GPS, telemetry, and real flight performance, linking structural reliability with operational robustness. Finally, a practical materials pathway was implemented through a dual-track strategy: PETG for rapid, low-cost prototyping, and carbon fiber composites as the benchmark for production-level performance. Nonlinear transient FEM analyses were carried out using Inventor Nastran under multiple load cases, including maximum motor acceleration, pitch maneuvers, and lateral impact at 40 km/h, and were validated against simplified analytical models. Experimental validation included bench and in-flight trials with integrated telemetry and autonomous features such as Return-to-Home, demonstrating functional robustness. The results show that the prototype flies correctly and that the chassis withstands the loads experienced during flight, including accelerations up to 4.2 G (41.19 m/${\mathrm{s}}^2$), abrupt changes in direction, and high-speed maneuvers reaching approximately 116 km/h. Quantitatively, safety factors of approximately 5.3 under maximum thrust and 1.35 during impact confirm sufficient structural integrity for operational conditions. In comparison with prior works reviewed in this study, the key contribution of this work lies in unifying advanced, crash-resilient FEM simulations with firmware-linked flight validation and a scalable material strategy, establishing a distinctive and comprehensive workflow for the development of sub-250 g UAVs. Full article

To address the challenges of low solar energy utilization efficiency and rapid recombination of photogenerated charge carriers in photocatalytic hydrogen evolution, this study successfully constructed a composite photocatalyst of ZnIn₂S₄ (ZIS) supported on N-doped hollow carbon spheres (N-HCS), denoted as ZIS/N-HCS, via a combination of template etching and in situ growth strategies. Characterization results demonstrate that this hollow structure possesses a high specific surface area (48.41 m²/g) and a narrowed bandgap (2.41 eV), achieve broad-spectrum light absorption, thereby enabling the catalyst to generate a local hot spot temperature of 136 °C under AM1.5G conditions. The optimized ZIS/N-HCS-0.30 sample exhibited a significantly enhanced photocurrent response (8.26 μA cm⁻²) and improved charge separation efficiency. When evaluated at a set solution temperature of 20 °C, the material exhibited a photocatalytic hydrogen evolution rate of 17.03 mmol g⁻¹·h⁻¹, which is 7.06 times higher than that of pure ZIS. Furthermore, it demonstrated excellent cycling stability. This work elucidates the synergistic role of the hollow photothermal structure in enhancing solar energy utilization and catalytic reaction kinetics, providing a new strategy for designing efficient solar-driven hydrogen production systems. Full article

Developing efficient photocatalysts is essential for sustainable wastewater treatment and tackling global water pollution. Graphitic carbon nitride (g-C₃N₄) is a promising material because it is active under visible light and chemically stable. However, its practical application is limited by fast recombination of charge carriers and a low surface area. In this study, we report a simple hydrothermal method to synthesize exfoliated porous g-C₃N₄ (E-PGCN) combined with Ti₃C₂ MXene to form a heterojunction composite that addresses these issues. Various characterization techniques (FTIR, XRD, XPS, SEM, BET) confirmed that adding MXene improves light absorption, increases surface area (53.7 m²/g for the composite versus 21.4 m²/g for bulk g-C₃N₄ (BGCN)), and enhances charge separation at the interface. Under UV-visible light irradiation with Rhodamine B (RhB) as the model pollutant, the E-PGCN/Ti₃C₂ MXene composite containing 3 wt% MXene demonstrated an impressive degradation efficiency of 93.2%. This performance is superior to BGCN (66.6%), E-PGCN (82.5%), and E-PGCN/Ti₃C₂ MXene-5 wt% composites (81%). This is due to the excess Mxene which caused agglomeration and reduced activity. Scavenger studies identified electron radicals as the dominant reactive species, with optimal activity at pH ~4.5. This enhanced performance, 1.4 times greater than BGCN and 1.13 times higher than E-PGCN, is ascribed to the synergistic interplay between the excellent electrical conductivity of MXene and the porous structural features of E-PGCN. This work highlights the importance of morphological engineering and heterojunction design for advancing metal-free photocatalysts, offering a scalable strategy for sustainable water purification. Full article

Aqueous zinc-ion batteries (AZIBs) have attracted considerable attention due to their intrinsic safety, low cost, and environmental friendliness. However, drastic volume expansion, sluggish reaction kinetics, and the insufficient structural stability of electrode materials still remain key challenges. In this work, a cascade structure-guided electron transport strategy was used to construct a vanadium nitride@carbon nanosheet/carbon nanofiber (VN@CNS/CNF) composite as a high-performance cathode for AZIBs. In this rationally engineered architecture, carbon-coated VN nanoparticles are uniformly anchored on a conductive carbon nanofiber network, forming a multidimensional interconnected structure that enables fast electron/ion transport and robust mechanical stability. The carbon shell effectively alleviates volume expansion and prevents VN nanoparticle agglomeration, while the continuous carbon fiber backbone reduces charge transfer resistance and enhances reaction kinetics. Benefiting from this synergistic structural design, the VN@CNS/CNF electrode delivers a high specific capacity of 564 mAh g⁻¹ at 0.1 A g⁻¹, maintains 99% capacity retention after 50 cycles, and retains 280 mAh g⁻¹ even at 8 A g⁻¹ after prolonged cycling. This study provides a new structural engineering strategy for vanadium nitride-based electrodes and provides strategic guidance for the development of fast-charging, durable aqueous zinc-ion batteries. Full article

The potential for structural health monitoring (SHM) in fibre-reinforced polymers (FRPs) using electrical resistance measurements (ERMs) has gained increasing attention, particularly in carbon fibre-reinforced polymers (CFRPs). Most existing studies are limited to single-axis measurements on coupon-scale specimens, whereas industrial applications demand scalable solutions capable of monitoring large areas, with more complex sensing configurations. Structural health monitoring (SHM) of carbon fibre-reinforced polymers (CFRPs) using electrical resistance measurements offers a low-cost, scalable sensing approach. However, predicting surface resistance between arbitrarily placed electrodes on unidirectional (UD) CFRP laminates remains challenging due to anisotropic conductivity and geometric variability. This study introduces a practical analytical model based on two geometry-dependent parameters, effective width and effective distance, to estimate resistance between any two electrodes arbitrarily placed on UD CFRP laminates with 0° or 90° fibre orientations. Validation through finite element (FE) simulations and experimental testing demonstrates good matching, confirming the model’s accuracy across various configurations. Results show that the dominant electrical current path aligns with the fibre direction due to the material’s anisotropic conductivity, allowing simplification to a single-axis resistance model. The proposed model offers a reliable estimation of surface resistance and provides a valuable tool for electrode array configuration design in CFRP-based SHM. This work contributes to enabling low-cost and scalable electrical sensing solutions for the real-time monitoring of composite structures in aerospace, automotive, and other high-performance applications. Full article

With the global energy structure transitioning towards clean and low-carbon alternatives, electrochemical energy storage technologies have emerged as pivotal enablers for achieving efficient renewable energy utilization and carbon neutrality objectives. However, conventional electrode materials remain constrained by inherent limitations, including low specific surface area, sluggish ion diffusion kinetics, and insufficient mechanical stability, which fundamentally hinder the synergistic fulfillment of high energy density, superior power density, and prolonged cycling durability. Three-dimensional printing technology offers a revolutionary paradigm for designing and fabricating carbon-based electrochemical energy storage devices. By enabling precise control over both the microstructural architecture and macro-scale morphology of electrode materials, this additive manufacturing approach significantly enhances energy/power densities, as well as cycling stability. Specifically, 3D printing facilitates biomimetic topological designs (e.g., hierarchical porous networks, vertically aligned ion channels) and functional hybridization strategies (e.g., carbon/metal oxide hybrids, carbon/biomass-derived composites), thereby achieving synergistic optimization of charge transfer kinetics and mechanical endurance. This review systematically summarizes recent advancements in 3D-printed carbon-based electrodes across major energy storage systems, including supercapacitors, lithium-ion batteries, and metal–air batteries. Particular emphasis is placed on the design principles of carbon-based inks, multiscale structural engineering strategies, and process optimization methodologies. Furthermore, we prospect future research directions focusing on smart 4D printing-enabled dynamic regulation, multi-material integrated systems, and artificial intelligence-guided design frameworks to bridge the gap between laboratory prototypes and industrial-scale applications. Through multidisciplinary convergence spanning materials science, advanced manufacturing, and device engineering, 3D-printed carbon electrodes are poised to catalyze the development of next-generation high-performance, customizable energy storage systems. Full article

In this study, fallen leaves of Azadirachta indica and Prunus dulcis were treated as waste materials for the production of energy-intensive bio-coal briquettes. The physical composition revealed that the moisture content ranged from 6.8% to 8.8%, fixed carbon from 10.7% to 14.0%, volatile matter from 71.2% to 77.1%, and ash content from 4.1% to 7.6%. The chemical structure of the biomass fuel, which included carbon, hydrogen, nitrogen, sulfur, and oxygen, was noted to be 44.56–50.69%, 7.12–7.33%, 0.14–0.25%, 0.47–0.79%, and 41.08–47.46%, respectively. The higher heating value ranged from 16.8 to 18.3 MJ/kg. With increasing pressure from 5 to 20 MPa, briquette density increased from 654 to 995 kg/m³, shatter index from 81% to 94%, durability from 67% to 92%, and resistance to water penetration from 57% to 77%. A low-pressure briquette (5 MPa) burned at a higher rate of 8.0 g/min, whereas a high-pressure briquette (20 MPa) burned at a lower rate of 2.5 g/min. All leaf types tested were able to boil 1000 mL of water with 100 g of briquettes in just 7 min. Full article

The rapid expansion of island and reef infrastructure has intensified the demand for sustainable concrete materials, yet the scarcity of conventional aggregates and freshwater severely constrains their supply. More critically, the fundamental bonding mechanism between steel reinforcement and coral aggregate concrete (CAC) remains poorly understood due to the highly porous, ion-rich nature of coral aggregates and the complex interfacial reactions at the steel–cement–coral interface. Moreover, the synergistic effect of polyoxymethylene (POM) fibers in modifying this interfacial behavior has not yet been systematically quantified. To fill this research gap, this study develops a C40-grade POM-fiber-reinforced CAC and investigates the composition–property relationship governing its bond performance with steel bars. A comprehensive series of pull-out tests was conducted to examine the effects of POM fiber dosage (0, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%), protective layer thickness (32, 48, and 67 mm), bar type, and anchorage length (2 d, 3 d, 5 d, and 6 d) on the interfacial bond behavior. Results reveal that a 0.6% POM fiber addition optimally enhanced the peak bond stress and restrained radial cracking, indicating a strong fiber-bridging contribution at the micro-interface. A constitutive bond–slip model incorporating the effects of fiber content and c/d ratio was established and experimentally validated. The findings elucidate the multiscale coupling mechanism among coral aggregate, POM fiber, and steel reinforcement, providing theoretical and practical guidance for the design of durable, low-carbon marine concrete structures. Full article

Football (soccer) is the world’s most widely played sport, but it carries a high incidence of traumatic injuries, particularly to the head, face, and lower limbs. Once regarded as a low-equipment discipline, the role of protective devices has expanded substantially in recent decades, both in injury prevention and in return-to-play strategies. This review provides a comprehensive overview of the historical evolution, typology, and materials of football protective equipment, with additional focus on regulatory frameworks, cultural acceptance, and illustrative cases from elite athletes. Shin guards remain the only mandatory device, yet the use of facial masks, headgear, braces, and orthoses is increasing, particularly following high-profile injuries. Advances in carbon fiber composites, thermoplastics, viscoelastic foams, and additive manufacturing have enabled lightweight, customized devices that balance protection with comfort and adherence. Beyond biomechanics, psychological reassurance, esthetics, durability, and hygiene strongly influence player compliance and perception. Despite this progress, critical challenges remain. Football lacks standardized testing protocols, clear certification pathways, and longitudinal studies on long-term outcomes. Evidence is particularly limited for youth athletes and newer categories of equipment. Looking ahead, the integration of wearable technologies, systematic hygiene and durability testing, and sustainable materials could transform protective gear into multifunctional tools for safety, monitoring, and performance optimization. Protective equipment in football has thus evolved into a multidisciplinary field at the intersection of medicine, engineering, psychology, and regulation. Future advances will depend on stronger collaboration between clinicians, researchers, governing bodies, and manufacturers to ensure safe, effective, and widely accepted protective solutions at all levels of the game. Full article

Carbon-fiber-reinforced silicon carbide (C/SiC) composite materials, as a kind of composite material with the characteristics of ceramics, have the following characteristics: high strength, high stiffness, low density, high temperature resistance, and high corrosion resistance. These characteristics make them widely applicable in aerospace, defense, automotive, and other high-performance industries. However, because of their anisotropy and inherent brittleness, ceramic-based composites are still difficult to process using conventional processing techniques. In this study, a technique of ultrasonic vibration-assisted micro-electrical discharge machining (micro-EDM) for the precise machining of two-dimensional (2D) C/SiC composites was proposed. The research mainly focused on an investigation of the material removal mechanism of C/SiC composites under ultrasonic vibration-assisted micro-EDM conditions. The erosion process was found to involve melting and vaporization of the SiC matrix, whereas the carbon fibers were removed by fragmentation and localized melting. In order to assess the effects of various process parameters on the material removal rate (MRR), single-factor experiments were performed initially. Afterwards, response surface methodology was used to optimize the MRR of C/SiC composites during ultrasonic vibration-assisted micro-EDM. A Plackett–Burman (PB) design was used to determine the parameters that have a significant effect on MRR. Based on these results, the optimum parameter range was obtained using the method of steepest ascent. Finally, a Box–Behnken design was used to determine the best machining parameters for improved performance. Full article

Material extrusion is a widely employed additive manufacturing technique with the functional capability of fabricating solid objects or cellular structures by depositing molten thermoplastic material in successive layers according to the designed path of deposition beads. Carbon fiber sandwich composites are advanced structures, ideal in applications that require high strength and stiffness, and low weight. In the present work, sandwich composites consisting of a carbon fiber-reinforced polyamide core—3D printed with a cubic pattern at 50% infill density—and carbon fiber fabric (CFF) skin, were fabricated using the hand lay-up method and experimentally investigated. The results showed that the tensile, flexural and impact strength of the sandwich composites increased by 64.5%, 24.5% and 69.0%, respectively, compared to unreinforced 3D printed specimens with 50% infill density, and by 24.3%, 18.8% and 56.3%, respectively, compared to unreinforced 3D printed specimens with 100% infill density. In addition, a reduction in the water absorption and the density of the sandwich composites was observed. Similar results were obtained for sandwich composites with one additional internal CFF layer. This work demonstrates that this specific combination of materials and manufacturing processes can be successfully employed for lightweight, water-resistant carbon fiber sandwich structures with improved mechanical strength. Full article

Driven by global economic growth and the rapid advancement of emerging technologies, the escalating demand for fossil fuels and hazardous chemicals has intensified, contributing to severe environmental degradation and widespread pollution. Hence, the demand for sustainable, eco-friendly solutions has become more urgent than ever. Since the industrial revolution, the atmospheric concentration of CO₂ has been on the rise, with reports suggesting a significant increase by 2080. To overcome this, more and more sustainable materials have been proposed as efficient adsorbents for CO₂. Biomass represents a green and sustainable platform for the production of materials with applications in various areas. Considering its non-toxic character, abundance, and low cost, biomass is frequently used as carbon feedstock. This paper focuses on the usage of biomass for the synthesis of efficient CO₂ adsorbents. This study addresses the influence of biomass composition on final uptake performance, offering a better insight into the role of each feedstock component in shaping the properties of the final material. In addition, the advantages and disadvantages of the carbon synthesis routes are presented, accompanied by various examples of materials and their performances. Overall, the current work focuses on multiple cases of biomass-derived carbons for CO₂ adsorption, covering aspects from synthesis to performance evaluation, while highlighting the current findings and existing challenges. Full article

Polyaniline (PANI), as a classical conducting polymer, has attracted significant attention in the field of energy storage due to its low cost, facile synthesis, environmental stability, and unique dual electronic/ionic conductivity. Particularly, one-dimensional (1D) nanostructures of PANI, such as nanowires and nanorods, exhibit superior electrochemical performance and cycling stability, attributed to their high surface area and efficient charge transport pathways. This review provides a comprehensive summary of recent advances in 1D PANI-based anode materials for lithium-ion, sodium-ion, and other types of rechargeable batteries. The specific capacity, rate performance, and long-term cycling behavior of these materials are discussed in detail. Moreover, strategies for performance enhancement through combination with carbon materials, metal oxides, and silicon, as well as chemical doping and structural modification, are systematically reviewed. Key challenges including electrochemical stability, structural durability, and large-scale fabrication are analyzed. Finally, the future directions in structural design, composite engineering, and commercialization of 1D PANI anode materials are outlined. This review aims to provide insight and guidance for the further development and practical application of PANI-based energy storage systems. Full article

To enhance the efficient utilization of industrial solid waste and support the low-carbon transition of cementitious materials, this study used steel slag, coal-fired slag, and desulfurization gypsum as the primary raw materials. A high-performance composite cementitious material system was developed based on the synergistic effects of physical activation (mechanical grinding) and chemical activation (alkali stimulation). This study systematically investigates the raw material characteristics, mix proportion optimization, mechanical behavior, and durability of composite cementitious materials through the integration of response surface optimization design and multi-scale analysis methods. The results indicate that the optimal mix proportions of the composite cementitious material are: 37.2% steel slag, 33.2% coal-fired slag, 9.6% desulfurized gypsum, 20% cement, 4% sodium silicate, and 0.1% superplasticizer. At this mix proportion, the measured 28-day average compressive strength of the composite cementitious material was 40.8 MPa, which closely matched the predicted value of 41.2 MPa from the response surface regression model, thereby confirming the model’s accuracy and applicability. The composite cementitious material demonstrated superior volume stability compared to ordinary cement under both water-curing and drying conditions. However, its freeze–thaw resistance and carbonation resistance were lower than those of cement. Therefore, considering these factors comprehensively, the composite cementitious material is recommended for application in road base and subbase layers. Full article