Composite Structures Research Articles

RCS-reduced patch antenna with wide frequency tuning range based on absorbing metasurface

A frequency-tunable patch antenna with reduced radar cross section (RCS) based on absorbing metamaterial is proposed. By controlling the external voltage of the varactor diodes, the working frequency of the patch can be adjusted. Through an investigation of the composite structure of the patch and absorbing metamaterial, RCS reduction is achieved over the entire wide tunable frequency range of the antenna. Measured results illustrate that the proposed patch antenna can dynamically operate in the range from 2.28 to 3.6 GHz with a gain variation of 7.1–8.7 dBi. Meanwhile, the RCS can be reduced by at least 7 dB and up to 20 dB in a fractional bandwidth of 44.9% of the antenna under a normal incidence. In comparison to conventional RCS-reduced antennas, the proposed one features a broader frequency tuning range and has potential value in wideband radar systems under complex electromagnetic interference environments.

Studies of Protein Binding to Biomimetic Membranes Using a Group of Uniform Materials Based on Organic Salts Derived From 8-Anilino-1-naphthalenesulfonic Acid.

Tuning the 8-anilino-1-naphthalenesulfonic acid (ANS) structure usually requires harsh conditions and long reaction times, which can result in low yields. Herein, ANS was modified to form an ANS group of uniform materials based on organic salts (GUMBOS), prepared with simple metathesis reactions and distinct cations, namely tetrabutylammonium (N4444), tetrahexylammonium (N6666), and tetrabutylphosphonium (P4444). These ANS-based GUMBOS were investigated as fluorescent probes for membrane binding studies with four proteins having distinct physicochemical properties. Liposomes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine were employed as membrane models as a result of their ability to mimic the structure and chemical composition of cell membranes. Changes in fluorescence intensity were used to monitor protein binding to liposomes, and adsorption data were fitted to a Freundlich-like isotherm. It was determined that [N4444][ANS] and [P4444][ANS] GUMBOS have enhanced optical properties and lipophilicity as compared to parent ANS. As a result, these two GUMBOS were selected for subsequent protein-membrane binding studies. Both [N4444][ANS] and [P4444][ANS] GUMBOS and parent ANS independently reached membrane saturation within the same concentration range. Furthermore, distinct fluorescence responses were observed upon the addition of proteins to each probe, which demonstrates the impact of properties such as lipophilicity on the binding process. The relative maintenance of binding cooperativity and maximum fluorescence intensity suggests that proteins compete with ANS-based probes for the same membrane binding sites. Finally, this GUMBOS-based approach is simple, rapid, and involves relatively small amounts of reagents, making it attractive for high-throughput purposes. These results presented herein can also provide relevant information for designing GUMBOS with ameliorated properties.

Mechanical characteristics of auxetic composite honeycomb sandwich structure under bending

Auxetic honeycomb sandwich structures (AHS) composed of a single material generally exhibit comparatively lower energy absorption (EA) and platform stress, as compared to traditional non-auxetic sandwich structures (TNS). To address this limitation, the present study examines the use of aluminum foam (AF) as a filling material in the re-entrant honeycomb sandwich structure (RS). Filling the AHS with AF greatly enhances both the EA and platform stress in comparison to filling the TNS with AF, while the auxetic composite honeycomb sandwich structure effectively addresses interface delamination observed in traditional non-auxetic composite sandwich structures. Subsequently, the positive–negative Poisson’s ratio coupling designs are proposed to strengthen the mechanical features of a single honeycomb sandwich structure. The analysis results show that the coupling structure optimizes the mechanical properties by leveraging the high bearing capacity of the hexagonal honeycomb and the great interaction between the re-entrant honeycomb and the filling material. In contrast with traditional non-auxetic sandwich structures, the proposed auxetic composite honeycomb sandwich structures demonstrate superior EA and platform stress performance, suggesting their immense potential for utilization in protective engineering.

Recent Advancements in Ascribing Several Platinum Free Electrocatalysts Pertinent to Hydrogen Evolution from Water Reduction.

The advancement of a sustainable and scalable catalyst for hydrogen production is crucial for the future of the hydrogen economy. Electrochemical water splitting stands out as a promising pathway for sustainable hydrogen production. However, the development of Pt-free electrocatalysts that match the energy efficiency of Pt while remaining economical poses a significant challenge. This review addresses this challenge by highlighting latest breakthroughs in Pt-free catalysts for the hydrogen evolution reaction (HER). Specifically, we delve into the catalytic performance of various transition metal phosphides, metal carbides, metal sulphides, and metal nitrides toward HER. Our discussion emphasizes strategies for enhancing catalytic performance and explores the relationship between structural composition and the performance of different electrocatalysts. Through this comprehensive review, we aim to provide insights into the ongoing efforts to overcome barriers to scalable hydrogen production and pave the way for a sustainable hydrogen economy.

Ni migration on porous yttria-stabilized zirconia and yttria-micropatterned fuel electrodes in solid oxide fuel cells

This study investigates the mechanism of Ni migration and methods for preventing Ni migration by utilizing ceramic obstacles that can block or slow Ni movement during solid oxide fuel cell (SOFC) operation. A patterned thin-Ni model anode on mirror-polished yttria-stabilized zirconia (YSZ) substrate exhibited dynamic movement during operation, as reported previously. In this study, we attempt to elucidate the mechanism of Ni migration that occurs only on the surface of solid-state Ni by blocking or slowing this movement using porous patterns of different materials. Porous micropatterns of 100 % YSZ and 80 wt% yttria (Y2O3) + YSZ composites were fabricated on a YSZ electrolyte, and velocity changes and blocking of Ni were observed. The porous YSZ structure changed the velocity of the Ni. In contrast, no Ni migration occurred in the Y2O3/YSZ composite porous structure, despite migration occurring in the neighboring smooth YSZ area in the same cell. The Ni-migrated areas were separated by the Y2O3/YSZ porous area, indicating that Ni migration was not caused by microscale differences in temperature or supplied gas diffusion, and Ni moved only on the cell surface, not via Ni-containing gases because temperatures and gases cannot form micropatterns.

Mechanical and thermal characterization of elastomer modified polypropylene hybrid composites reinforced with hazelnut shell and wollastonite fillers

AbstractThe demand for sustainable and recyclable materials in industrial applications has led to a surge in interest in green composites, particularly those incorporating natural fillers derived from agro‐food industry waste. This study investigates the mechanical and thermal properties of polypropylene (PP) hybrid composites filled with hazelnut shell and wollastonite, along with the effect of styrene‐ethylene/butylene‐styrene (SEBS) and SEBS‐g‐maleic anhydride (SEBS‐g‐MA) compatibilizers. Various characterization techniques, including tensile, flexural, and impact tests, as well as differential scanning calorimetry (DSC), thermogravimetry (TGA), and scanning electron microscopy (SEM) analyses, were employed to evaluate the composites. Results demonstrate that the addition of wollastonite significantly improves mechanical properties, while hazelnut shell filler affects thermal behavior and stability. SEBS and SEBS‐g‐MA compatibilizers enhance impact resistance; however, they lead to a decrease in other mechanical properties. DSC and TGA analyses demonstrate changes in crystallization behavior and thermal stability due to filler and compatibilizer incorporation. SEM microstructure images show the distribution of SEBS and SEBS‐g‐MA within the composite structure, affecting mechanical and thermal properties. Overall, this study highlights the importance of filler selection, compatibilizer addition, and their distribution in attaining desired properties for industrial applications. Future research should focus on optimizing formulations for specific uses and assessing long‐term performance under real‐world conditions.

Composite cores of monopoles and Alice rings in spin-2 Bose-Einstein condensates

We show that energy relaxation causes a point defect in the uniaxial-nematic phase of a spin-2 Bose-Einstein condensate to deform into a spin-Alice ring that exhibits a composite core structure with distinct topology at short and long distances from the singular line. An outer biaxial-nematic core exhibits a spin half-quantum vortex structure with a uniaxial-nematic inner core. By numerical simulation, we demonstrate a dynamical oscillation between the spin-Alice ring and a split-core hedgehog configuration via the appearance of ferromagnetic rings with associated vorticity inside an extended core region. We further show that a similar dynamics is exhibited by a spin-Alice ring surrounding a spin-vortex line resulting from the relaxation of a monopole situated on a spin-vortex line in the biaxial-nematic phase. In the cyclic phase, similar states are shown instead to form extended phase-mixing cores containing rings with fractional mass circulation or cores whose spatial shape reflects the order-parameter symmetry of a cyclic inner core, depending on the initial configuration. Published by the American Physical Society 2024

Comparative study on tensile and morphological properties of resin and rice husk reinforced polymer composite gyroid lattice structures

Abstract This study aims to compare the tensile behaviour of 3d printed resin and rice husk-reinforced resin-based gyroid lattice structures. The work was completed in two phases, firstly a resin gyroid lattice structure with two design configurations of unit cell sizes (3, 4, 5, and 6) and solidity percentages (30, 40, and 50) was developed according to the ASTM638 (4) standard. The 12 designs were manufactured using VAT polymerization additive manufacturing and investigated for tensile strength. In the second phase, the poorest tensile testing results were chosen to develop the rice husk-reinforced resin samples with a mixing proportion of 10-20-30%. The experiment results revealed that the fracture is localized inside the gauge length according to the standard. Remarkably, the rice husk composite-based gyroid lattice samples exhibit 4.29, 6.55, and 9.35 times higher tensile strength than the selected resin sample (U3-30). Additionally, a homogeneous distribution of rice husk particles has been observed in the micrograph analysis (SEM).

Anthropogenic Eutrophication Drives Major Food Web Changes in Mwanza Gulf, Lake Victoria

AbstractDiscerning ecosystem change and food web dynamics underlying anthropogenic eutrophication and the introduction of non-native species is necessary for ensuring the long-term sustainability of fisheries and lake biodiversity. Previous studies of eutrophication in Lake Victoria, eastern Africa, have focused on the loss of endemic fish biodiversity over the past several decades, but changes in the plankton communities over this same time remain unclear. To fill this gap, we examined sediment cores from a eutrophic embayment, Mwanza Gulf, to determine the timing and magnitude of changes in the phytoplankton and zooplankton assemblages over the past century. Biogeochemical proxies indicate nutrient enrichment began around ~ 1920 CE and led to rapid increases in primary production, and our analysis of photosynthetic pigments revealed three zones: pre-eutrophication (prior to 1920 CE), onset of eutrophication with increases in all pigments (1920–1990 CE), and sustained eutrophication with cyanobacterial dominance (1990 CE–present). Cladoceran remains indicate an abrupt decline in biomass in ~ 1960 CE, in response to the cumulative effects of eutrophication and lake-level rise, preceding the collapse of haplochromine cichlids in the 1980s. Alona and Chydorus, typically benthic littoral taxa, have remained at relatively low abundances since the 1960s, whereas the abundance of Bosmina, typically a planktonic taxon, increased in the 1990s concurrently with the biomass recovery of haplochromine cichlid fishes. Overall, our results demonstrate substantial changes over the past century in the biomass structure and taxonomic composition of Mwanza Gulf phytoplankton and zooplankton communities, providing a historical food web perspective that can help understand the recent changes and inform future resource management decisions in the Lake Victoria ecosystem.

Assessing the Sound and Heat Insulation Characteristics of Layered Nonwoven Composite Structures Composed of Meltblown and Recycled Thermo-Bonded Layers

Assessing the Sound and Heat Insulation Characteristics of Layered Nonwoven Composite Structures Composed of Meltblown and Recycled Thermo-Bonded Layers

Tunable optical devices with multiple plasmon-induced transparency based on graphene-black phosphorus hybrid metasurface

In this research, we propose a simple and novel graphene-black phosphorus composite structure. Through the coupling mechanism of bright–bright mode, four layers of graphene and one layer of black phosphorus produce a quadruple plasmon-induced transparency (PIT) effect. The response of the proposed structure to the angle of polarized light is investigated, and it is found that the sensitivities of graphene and black phosphorus to the polarization angle of light are different. In addition, the dynamic regulation of PIT by the Fermi level of graphene and the carrier concentration of black phosphorus are discussed. The modulation depths of the fivefold optical switching are 96%, 99%, 87%, 93%, and 80%, respectively. The quadruple PIT can also be converted into triple PIT, in which single, dual, or triple optical switching are realized, respectively. Finally, with the change in the refractive index of the environment medium, the sensitivity response of the proposed structure is as high as 4.790 THz⋅RIU−1. We believe that this research will contribute to the development of optical switches, modulators, and sensors.

New Accomplishments on the Equivalence of the First-Order Displacement-Based Zigzag Theories through a Unified Formulation

The paper presents a critical review and new accomplishments on the equivalence of the first-order displacement-based zigzag theories for laminated composite and sandwich structures. Zigzag theories (ZZTs) have widely spread among researchers over the last few decades thanks to their accuracy in predicting the response of multilayered composite and sandwich structures while retaining the simplicity of their underlying equivalent single-layer (ESL) theory. The displacement field consists of two main contributions: the global one, able to describe the overall structural behaviour, and the local layer-wise one that considers the transverse shear continuity at the layer interfaces that describe the “zigzag” displacement pattern typical of multilayered structures. In the framework of displacement-based linear ZZTs, various assumptions have been made on the local contribution, and different theories have been deduced. This paper aims to provide a unified formulation for first-order ZZTs, highlighting some common aspects and underlying equivalencies with existing formulations. The mathematical demonstrations and the numerical examples prove the equivalence of the approaches to characterising local zigzag enrichment. Finally, it is demonstrated that the kinematic assumptions are the discriminants of the ZZTs’ accuracy.

Slate–Cork Laminate Enhanced with Silicone for Habitat Industry Application

This study investigates the feasibility of using a composite material comprising slate reinforced with cork sheets for architectural purposes like facades and wall coverings. The research involves the comprehensive characterisation of both slate and cork materials along with the evaluation of the silicone adhesive used in their bonding process, specifically Sikasil® HT from SIKA®. It was found that both slate and cork exhibited low wettability, which was enhanced through cold plasma treatment. Subsequently, a composite sandwich structure was fabricated and subjected to impact testing in a drop tower, along with fire resistance evaluations. The fire tests revealed that when subjected to a flame of 900 °C for 15 min, the slate alone heated rapidly, reaching 500 °C within 3 min on the side opposite to the flame. However, the sandwich structure reached 260 °C on the cork side (opposite to the flame) at 7.5 min, maintaining this temperature until the deterioration or detachment of the cork between 11 and 12 min. This provided insulation and delayed ignition. The sandwich structure maintained its fire resistance due to the insulating properties of cork and the superior thermal resistance of silicone compared to other adhesives up to 260 °C. Overall, the results suggest the potential suitability of this sandwich structure for architectural applications. Its favourable adhesion properties and acceptable fire resistance indicate that it could serve as a viable alternative for construction materials in architectural contexts.

A Human-Scale Clinically-Ready Electromagnetic Navigation System for Magnetically-Responsive Biomaterials and Medical Devices.

Magnetic navigation systems are used to precisely manipulate magnetically responsive materials enabling the realization of new minimally invasive procedures using magnetic medical devices. Their widespread applicability has been constrained by high infrastructure demands and costs. we report on a portable electromagnetic navigation system, the Navion, which is capable of generating a large magnetic field over a large workspace. The system is easy to install in hospital operating rooms and transportable through healthcare facilities, aiding in the widespread adoption of magnetically responsive medical devices. First, we introduce our design and implementation approach for the system and characterize its performance. Next, we demonstrate in vitro navigation of different microrobot structures using magnetic field gradients and rotating magnetic fields. Spherical permanent magnets, electroplated cylindrical microrobots, microparticle swarms, and magnetic composite bacteria-inspired helical structures are investigated. we also demonstrate the navigation of magnetic catheters in two challenging endovascular tasks: (1) an angiography procedure and (2) deep navigation within the circle of Willis. Catheter navigation is demonstrated in a porcine model in vivo to perform an angiography under magnetic guidance. This article is protected by copyright. All rights reserved.

Multilayer boron doped Si@SiOx/C from Si-Ca alloy for lithium-ion battery anodes

SiOx has been considered as a promising anode for next-generation lithium-ion batteries. However, the poor rate performance caused by the low electrical conductivity is a bottleneck of its application. Approaches involving carbon composites, boron doping and two-dimensional structure have been pursued to improve the electrical conductivity. In this work, through the combination of these strategies, a multilayer boron doped Si@SiOx/C composites are fabricated by a chemical exfoliation of CaSi2 with B2O3 and CaCO3. The production exhibits favorable properties for lithium-ion battery anodes, such as proper specific surface area, complete multilayer structure, boron doped and carbon composite structure. The as-obtained B-Si@SiOx/C-700 delivers a capacity of 659.3 mAh g−1 after 500 cycles at 1 A g−1. Especially, at 4 A g−1, the capacity retention of the B-Si@SiOx/C-700 anode is still 40.9 % of its average discharge capacity at 0.2 A g−1. The capacitive contribution to the total Li+ storage capacity for the B-Si@SiOx/C-700 electrode is 83.6 % at 1.0 mV s−1. This work presents a simple and efficient strategy to construct a multilayer doped structure to improve electrochemical properties.

Comparison of MAF-32 and a One-Pot Synthesized Superparamagnetic Iron Oxide/MAF-32 Composite for the Adsorption of Diclofenac

The global presence of pharmaceutical pollutants in water sources represents a burgeoning public health concern. Recent studies underscore the urgency of addressing this class of emerging contaminants. In this context, our work focuses on synthesizing a composite material, FexOy/MAF-32, through a streamlined one-pot reaction process, as an adsorbent for diclofenac, an emerging environmental contaminant frequently found in freshwater environments and linked to potential toxicity towards several organisms such as fish and mussels. A thorough characterization was performed to elucidate the structural composition of the composite. The material presents magnetic properties attributed to its superparamagnetic behavior, which facilitates the recovery efficiency of the composite post-diclofenac adsorption. Our study further involves a comparative analysis between the FexOy/MAF-32 and a non-magnetic counterpart, comprised solely of 2-ethylimidazolate zinc polymer. This comparison aims to discern the relative advantages and disadvantages of incorporating magnetic iron oxide nanoparticles in the contaminant removal process facilitated by a coordination polymer. Our findings reveal that even a minimal incorporation of iron oxide nanoparticles substantially enhanced the composite’s overall performance in pollutant adsorption.

Natural Fibre and Hybrid Composite Thin-Walled Structures for Automotive Crashworthiness: A Review

Natural fibres, valued for their low density, cost-effectiveness, high strength-to-weight ratio, and efficient energy absorption, are increasingly emerging as alternatives to synthetic materials in green composites. Although they cannot fully replace synthetic counterparts, like carbon, in structural applications due to their inferior mechanical performance, combining them through hybridization presents a potential solution. This approach promotes a balance between environmental benefits and mechanical efficiency. Recently, the transportation sector has shifted its focus towards delivering lightweight and crashworthy composite structures to improve vehicle performance, address safety concerns, and minimise environmental impact through the use of eco-friendly materials. The crashworthiness of energy absorbers, typically thin-walled structures, is influenced by several factors, including their material and geometric design. This paper presents a comprehensive overview of recent studies focused on the crashworthiness of fibre-reinforced, thin-walled composites under axial crushing. It explores different aspects, such as their materials, cross-sections, stacking sequences, triggering or filling mechanisms, and the effect of loading rate speed. Emphasis is placed on natural-fibre-based materials, including a comparative analysis of synthetic ones and their hybridization. The primary objective is to review the progress of solutions using green composites as energy absorbers in the automotive industry, considering their lightweight design, crashworthiness, and environmental sustainability.

Liability for Violation of the Obligation of Care in the Criminal Code of the Republic of Poland

The problem of non-fulfilment or improper fulfillment by parents (persons who replace them) of childcare responsibilities exists in all countries, regardless of the form of government, state system, and income level of the population. Ukraine has been in the process of integration with the European Union for a long time, so it is useful to study the foreign legislative approach to the regulation of responsibility for the violation of these obligations. The purpose of the article is to study the Polish experience of establishing criminal liability for non-fulfilment of child care obligations. In the research dogmatic, systemic-structural, statistical, historical-legal, formal-legal methods were used. Attention is paid to the legislation of the Republic of Poland, which provides for the right and duty of parents to care for and raise children. The genesis of the criminal law regarding responsibility for violation of these duties in the Criminal Code of 1932, 1969, and 1997 is given. Statistical data on the number of criminal proceedings and persons convicted of this criminal offense (2009–2020) are summarized. The peculiarities of the structure of the crime composition provided for in Art. 210 of the Criminal Code of the Republic of Poland were studied; objective and subjective signs. The analysis was carried out on the basis of the doctrine of Polish criminal law and the practice of courts of general jurisdiction, in particular the Supreme Court of the Republic of Poland. The practice of the Constitutional Tribunal of the Republic of Poland was used. Based on the results of the research, conclusions were formulated regarding objects of criminal law protection; objective and subjective side and subject composition. The differentiation of criminal liability in case of causing death to the victim was noted. The legislator also provided in cases of this crime the possibility of notifying the competent family court about the expediency of deprivation or limitation of parental or guardian rights in case of committing a crime to the detriment of a minor or in complicity with him. The separation of an independent structural section (subsection) in the Criminal Code of Ukraine, which includes criminal offenses against the family, as well as the improvement of criminal legal measures against persons who have committed such crimes, is supported.

Novel binary regulated silicon-carbon materials as high-performance anodes for lithium-ion batteries.

The massive volume dilation, unsteady solid electrolyte interphase, and weak conductivity about Si have failed to bring it to practical applications, although its potential capacity is up to 4200 mAh g-1. For solving these problems, novel binary regulated silicon-carbon materials (Si/BPC) were done by a sol-gel procedure combined with single carbonization. Analytical techniques were systematically utilized to examine the effects of element doping at several gradients on morphology, structure and electrochemical properties of composites, thus the optimal content was identified. Si/BPC preserves a discharge specific capacity of 1021.6 mAh g-1with a coulomb efficiency of 99.27% after 180 cycles at 1000 mA g-1, within the upgrade than single-doped and undoped. In rate test, it has a specific capacity of 1003.2 mAh g-1at a high current density of 5000 mA g-1, quickly back towards 2838.6 mAh g-1at 200 mA g-1. The inclusion of B and P elements is linked to the electrochemical characteristics. In the co-doped carbon layers, the synergistic impact of doping B and P accelerates the diffusion kinetics of lithium ions, boosts diffusion rate of Li+, offers low electrochemical impedance (45.75 Ω). This brings more defects to provide transport carriers and induces a substantial amount of electrochemically active sites, which fosters the storage of Li+, thus making silicon material electrochemically more active and potential.

Three-Dimensional Finite Element Modeling of Ultrasonic Vibration-Assisted Milling of the Nomex Honeycomb Structure

Machining of Nomex honeycomb composite (NHC) structures is of critical importance in manufacturing parts to the specifications required in the aerospace industry. However, the special characteristics of the Nomex honeycomb structure, including its composite nature and complex geometry, require a specific machining approach to avoid cutting defects and ensure optimal surface quality. To overcome this problem, this research suggests the adoption of RUM technology, which involves the application of ultrasonic vibrations following the axis of revolution of the UCK cutting tool. To achieve this objective, a three-dimensional finite element numerical model of Nomex honeycomb structure machining is developed with the Abaqus/Explicit software, 2017 version. Based on this model, this research examines the impact of vibration amplitude on the machinability of this kind of structure, including cutting force components, stress and strain distribution, and surface quality as well as the size of the chips. In conclusion, the results highlight that the use of ultrasonic vibrations results in an important reduction in the components of the cutting force by up to 42%, improves the quality of the surface, and decreases the size of the chips.