Composite Structures Research Articles

Investigating of epoxy nanocomposites structure and properties that contain both pristine and aminosilane-treated silicon carbide (SiC) particles

This article presents a methodology for functionalization of silicon carbide (SiC) through chemical modification using γ-aminopropyltriethoxysilane (APTES) and its subsequent dispersion in an epoxy composition. The research revealed that functionalizing SiC particles with γ-aminopropyltriethoxysilane (SiC(APTES)) enhanced their chemical compatibility with the epoxy composition, facilitating the dispersion of SiC particles. Furthermore, it was observed that the functionalization of the filler had a profound impact on the structure, curing kinetics, and physical and mechanical properties of epoxy nanocomposites. The addition of SiC(APTES) into the epoxy composition resulted in a significant reinforcement of the material. Specifically, the flexural stress and flexural modulus of elasticity increased by 179% and 74%, respectively, while the impact strength experienced a remarkable improvement of 462%. Additionally, the tensile strength and tensile modulus of elasticity increased by 83% and 70%, respectively, compared to the epoxy composite without SiC. The application of SiC(APTES) also played a crucial role in initiating the polymerization process through the involvement of reactive amino groups, leading to a reduction in the initial curing temperature and an amplification of the thermal effects of the polymerization reaction. Moreover, the presence of functionalized SiC significantly influenced the structure of the epoxy composite, thereby contributing to its enhanced strength. In summary, the inclusion of SiC in the epoxy composition not only bolstered the material but also improved its thermal stability.

Manufacturing Shape-Controllable Flexible PEDOT/rGO Composite Electrodes for Planar Micro-Supercapacitors.

Flexible electronic products, with their characteristics of flexibility and wearability, have attracted significant attention and have become an important direction in the research and development of the electronics industry. Planar micro-supercapacitors (MSCs) with flexible composite electrodes can provide reliable energy support for these products, propelling their further development. The research employed a quick, effective, and environmentally friendly method of laser scribing to create shape-controllable flexible composite electrodes on composite films of Poly(3,4-ethylenedioxythiophene) and graphene oxide (PEDOT/GO), which were subsequently assembled into MSCs. An analysis of the composite electrode morphology, structure, and elemental distribution was conducted through the utilization of SEM, TEM, and XPS techniques. Following this, a comprehensive evaluation of the electrochemical performance of the flexible MSCs was carried out, which included cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and assessment of cyclic stability. The analysis of the CV results indicated that the MSCs achieved the areal capacitance of 5.78 mF/cm2 at 5 mV/s. After 5000 cycles at a current density of 0.05 mA/cm2, the capacitance retention rate was 85.4%. The high areal capacitance and strong cycle stability of MSCs highlight the potential of PEDOT/reduced graphene oxide (PEDOT/rGO) electrodes in electrode applications.

Composite attention mechanism network for deep contrastive multi-view clustering

Contrastive learning-based deep multi-view clustering methods have become a mainstream solution for unlabeled multi-view data. These methods usually utilize a basic structure that combines autoencoder, contrastive learning, or/and MLP projectors to generate more representative latent representations for the final clustering stage. However, existing deep contrastive multi-view clustering ignores two key points: (i) the latent representations projecting from one or more layers of MLP or new representations directly obtained from autoencoder fail to mine inherent relationship inner-view or cross-views; (ii) more existing frameworks only employ a one or dual-contrastive learning module, i.e., view- or/and category-oriented, which may result in the lack of communication between latent representations and clustering assignments. This paper proposes a new composite attention framework for contrastive multi-view clustering to address the above two challenges. Our method learns latent representations utilizing composite attention structure, i.e., Hierarchical Transformer for each view and Shared Attention for all views, rather than simple MLP. As a result, the learned representations can simultaneously preserve important features inside the view and balance the contributions across views. In addition, we add a new communication loss in our new dual contrastive framework. The common semantics will be brought into clustering assignments by pushing clustering assignments closer to the fused latent representations. Therefore, our method will provide a higher quality of clustering assignments for the segmentation problem of unlabeled multi-view data. The extensive experiments on several real data demonstrate that the proposed method can achieve superior performance over many state-of-the-art clustering algorithms, especially the significant improvement of an average of 10% on datasets Caltech and its subsets according to accuracy.

Elucidation of trap energies of Gamma-irradiated BaMgAl10O17: Ce3+ phosphors for dosimetry applications

AbstractThis paper presents a comprehensive examination of the thermoluminescence properties of BaMgAl10O17: Ce (BAM: Ce) phosphors, which were synthesized via the combustion method. The study employs five distinct approaches to determine the kinetic parameters for individual traps. To investigate the structural, morphological, and elemental composition of the samples, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were utilized. The photoluminescence spectra revealed a broad emission centered around 420 nm upon 330 nm excitation. By subjecting the phosphors to γ doses ranging from 5 to 5 kGy and conducting TL glow curve analysis, the kinetic characteristics of the BAM: Ce phosphors were determined. The linear dose–response was observed for 5–50 Gy, indicating a high sensitivity value. Additionally, there is a consistent estimation of trap energy across various methods. It is also worth noting that the phosphor exhibits a very low minimum detectable dose, estimated to be in the microgray range, making BAM: Ce a strong candidate for low gamma dosimetry applications.

Enhanced hyaline cartilage formation and continuous osteochondral regeneration via 3D-Printed heterogeneous hydrogel with multi-crosslinking inks

The unique gradient structure and complex composition of osteochondral tissue pose significant challenges in defect regeneration. Restoration of tissue heterogeneity while maintaining hyaline cartilage components has been a difficulty of an osteochondral tissue graft. A novel class of multi-crosslinked polysaccharide-based three-dimensional (3D) printing inks, including decellularized natural cartilage (dNC) and nano-hydroxyapatite, was designed to create a gradient scaffold with a robust interface-binding force. Herein, we report combining a dual-nozzle cross-printing technology and a gradient crosslinking method to create the scaffolds, demonstrating stable mechanical properties and heterogeneous bilayer structures. Biofunctional assessments revealed the remarkable regenerative effects of the scaffold, manifesting three orders of magnitude of mRNA upregulation during chondrogenesis and the formation of pure hyaline cartilage. Transcriptomics of the regeneration site in vivo and scaffold cell interaction tests in vitro showed that printed porous multilayer scaffolds could form the correct tissue structure for cell migration. More importantly, polysaccharides with dNC provided a hydrophilic microenvironment. The microenvironment is crucial in osteochondral regeneration because it could guide the regenerated cartilage to ensure the hyaline phenotype.

In-situ synthesis of coral reef-like synergistic zinc cobalt oxide and zinc manganese oxide composite as a battery-type electrode material for supercapacitors

Recently, in-situ preparation of metal oxide composite structures has gained much importance in fabricating electrode materials for energy storage and conversion devices because of its advantageous properties of beneficial interfacial contact, high conductivity, good synergism, short ion diffusion distance, better electrochemical performance, etc. Binary transition metal oxides (BTMOs) are given great attention for their significant electrochemical performances over primary MOs because of the two metal ions with different valent states for the redox reactions. In this study, we synthesize zinc cobalt oxide (ZnCo2O4) and zinc manganese oxide (ZnMn2O4) composite via a solvothermal synthetic method. The existence of both phases is identified using an X-ray diffraction analysis (XRD). The unique coral reef-like structures of the composite electrode are analysed via field emission scanning electron microscopy, and the nanostructure was identified using transmission electron microscopy. The X-ray photoelectron spectroscopy confirms the surface oxidation states of the composite and supports the XRD analysis. The synergetic composite electrode provides a large surface area of 50.86 m2 g−1 with many pores. The composite electrode has a specific capacity of 250 C g−1 at 1 A g−1. The ZCO/ZMO composite demonstrated impressive stability, retaining a specific capacity of 180 C g−1 at 6 A g−1 over 5000 cycles.

Mechanical property characterizations of woven natural fiber-reinforced polymers 3D printed through a laminated object manufacturing process

ABSTRACT The mechanical properties of woven natural fiber reinforced polymers additively manufactured through Laminated Object Manufacturing (LOM) technology are investigated in this paper. The benefits of both the material and manufacturing process were combined into a sustainable practice, as a potential alternative to traditional synthetic composite materials made from nonrenewable crude oil with limited end-of-life alternatives. Woven jute fiber reinforcements are used to strengthen both synthetic and bio- thermoplastic polymers in creating highly biodegradable composite structures. Such materials, as one of the prospective alternatives for synthetic composites, can be used in many engineering fields such as automobile panels, construction materials, and commodity and recreational products including sports and musical instruments. A LOM 3D printer prototype was designed and built by the authors. All woven jute/polymer biocomposite test specimens made using the built prototype in this study had their mechanical (both tensile and flexural) properties assessed using ASTM test standards and then compared to similar values measured from pure polymer specimens. Improved mechanical characteristics were identified and analyzed. Finally, SEM imaging was performed to identify the polymer infusion and fiber-matrix bonding conditions.

Characterization and radiation shielding efficiency of MWCNT/shape memory ternary blend composite films

In this study, the structural, X-ray and gamma-ray, and neutron shielding properties of shape memory ternary blend/multi-walled carbon nanotube (MWCNT) composite films were investigated. The composition of the composite films was defined as (100-x) poly (ε-caprolactone) (PCL):polyethylene glycol (PEG):polyvinyl chloride (PVC) + xMWCNT, where x = 0, 1, 3, 5% (mole percentage). The ternary blend/MWCNT composite films were characterized using Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). Thermal results showed that the degradation temperatures of composite materials with two degradation curves increased with increasing MWCNT percentage. The appearance of the MWCNT signal along with the characteristic polymer signals in the XRD pattern may be evidence that MWCNT is homogeneously distributed in the polymer blend. The mass attenuation coefficients (MAC), half-value layer (HVL), mean free path (MFP), and effective atomic numbers (Z_eff) of the composite films were experimentally measured over an energy range of 8.04–383.85 keV. Additionally, the equivalent dose rates for fast neutrons were measured, and the exposure buildup factor (EBF) and fast neutron removal cross-section (Σ_R) were theoretically calculated. The proton and alpha shielding parameters of the ternary blend/MWCNT composite films were determined, revealing that the inclusion of higher amounts of MWCNTs in the composite structure significantly improved capability of the films in shielding against radiation and neutrons.

Aging of deep venous thrombosis in-vivo using polarization sensitive optical coherence tomography

Deep venous thrombosis (DVT) is a medical condition with significant post-event morbidity and mortality coupled with limited treatment options. Treatment strategy and efficacy are highly dependent on the structural composition of the thrombus, which evolves over time from initial formation and is currently unevaluable with standard clinical testing. Here, we investigate the use of intravascular polarization-sensitive optical coherence tomography (PS-OCT) to assess thrombus morphology and composition in a rat DVT model in-vivo, including changes that occur over the thrombus aging process. PS-OCT measures tissue birefringence, which provides contrast for collagen and smooth muscle cells that are present in older, chronic clots. Thrombi in the inferior vena cava of two cohorts of rats were imaged in-vivo with intravascular PS-OCT at 24 hours (acute, nrats = 3, 73 cross-sections) or 28 days (chronic, nrats = 4, 41 cross-sections) after thrombus formation. Co-registered histology was labelled by an independent pathologist to establish ground-truth clot composition. Automated analysis of OCT cross-sectional images differentiated acute and chronic thrombi with 97.6% sensitivity and 98.6% specificity using a linear discriminant model comprised of both polarization and conventional OCT metrics. These results support PS-OCT as a highly sensitive imaging modality for the assessment of DVT composition to differentiate acute and chronic thrombi. Intravascular PS-OCT imaging could be integrated with advanced catheter-based treatment strategies and serve to guide therapeutic decision-making and deployment, by offering an accurate assessment of DVT patients in real time.

Damping and Wear Behavior of 3D Woven Reinforced Structural Composites for Automotive Leaf Spring Applications

Damping and Wear Behavior of 3D Woven Reinforced Structural Composites for Automotive Leaf Spring Applications

Mass Spectrometry-Based Analyses of Carbon Nanodots: Structural Elucidation.

Carbon nanodots (CNDs) are nanomaterials with ubiquitous applications in health for diagnosis and treatments. The key to enhancing the applications of carbon nanodots in various fields lies on how deep its structure is understood. Here, we review the mass spectroscopy (MS) techniques employed for carbon nanodot analysis. We aimed to revive the use of MS to support the structural elucidation of carbon nanodots. General techniques used in nanomaterials characterization include laser desorption/ionization (LDI), matrix-assisted LDI (MALDI), inductively coupled plasma (ICP), and electrospray ionization (ESI) MS. For CNDs characterization, LDI-MS, MALDI-MS, and ESI-MS were employed. The techniques required further instrumentations of time-of-flight (TOF), for MALDI, and TOF, quadrupole (Q), and tandem (MS/MS) for ESI. LDI-MS could be applied to prove the surface and core structural composition of carbon nanodots. Meanwhile, MALDI-MS was used to elucidate the surface structures of CNDs. Finally, ESI-MS could provide significant insight into the carbon nanodots' structural composition and bonding patterns. In summary, MS could be combined with other techniques to unambiguously elucidate the structure of carbon nanodots.

Transport infrastructure and the spatial distribution of CO[formula omitted] emissions

This study presents an analysis of transport infrastructure projects and their effect on greenhouse gas emissions. Causal inter-regional spillover effects are estimated for the launch of the China Europe Railway Express using a spatial difference in differences estimator. The preferred Spatial Durbin Model reveals a small negative direct effect of approximately -3.5 percent and a more substantial positive indirect effect of around 12.7 percent. These results suggest a crowding out of pollutant heavy industries from the nodal regions into the periphery. We provide further evidence for this hypothesis by testing the impact on the respective regions’ structural composition. A number of robustness checks support causality of benchmark findings.

Response of rhizosphere microbial community structure and production performance of corn and soybean to belt planting mode

Soybean and corn strip cropping takes full advantage of the root characteristics and plant height differences between soybean and corn, which can improve crop photosynthesis and nutrient uptake as well as capitalize on the marginal effect of corn. However, there is not enough in-depth research on the effects of soybean and corn strip cropping modes on inter-root microbial communities and crop yield traits and their correlations, and the functional genes of inter-root microbes. In this study, the structural composition and functional genes of soil inter-root microbial communities under different strip cropping patterns of soybean and maize, Mode 1, Mode 2, and Mode 3, were studied using macro-genome high-throughput sequencing, and the yield traits of soybean and maize were determined and the correlation was understood, taking Zhonglian Soybean 1505 and Tiyu 108 maize as test materials at the experimental base of the Research Institute of Agricultural and Livestock Sciences, Xing'anmeng, Inner Mongolia. correlation between the two. The following results were found. Redundancy analysis found that rhizosphere microorganisms are mainly bacteria, followed by viruses, followed by archaea, and fungi are the least. Relatively speaking, viruses and bacteria are more susceptible to the influence of planting patterns than fungi. Alpha diversity analysis shows that the diversity index changes significantly during the peak flowering period. There is no difference between the other two stages. The diversity of maize rhizosphere microorganisms under Mode 1 or Mode 2 modes is higher than that under Mode 3 modes, while the diversity of soybean rhizosphere microorganisms under Mode 3 modes is higher than the other two modes. Profiling analysis found that different growth periods and planting patterns lead to varying degrees of changes in community structure. The dominant bacterial phyla include Pseudomonas, Actinobacteria, Bacteroidetes, and Streptococcus. The dominant genera of bacteria are rhizobia, pseudomonas, erythrobacteria, and pseudomonas. The relative abundance of slow root rhizobia in the three growth stages of maize rhizosphere is relatively low. The results of yield traits showed that corn yield under Mode 1 and Mode 2 planting was significantly higher than that under pattern III; soybean yield under pattern III planting was significantly higher than that under the other two patterns, indicating that pattern I or II planting is suitable for corn production, while Mode 3 planting mode is more suitable for soybean production. Correlation analysis showed that S_Massilis_putida was significantly and positively correlated with maize yield, and S_lysobacter_capsici was highly significantly and significantly positively correlated with the number of soybean plants per square meter, and the number of plants in 2 square meters. This study contributes to our further understanding of the classification of inter-root microorganisms and their functional relationships in maize and soybean under different conditions.

Curved Polymeric Sandwich Composites Subjected to Air Shock: An Experimental Investigation

Abstract Background The vulnerability of polymeric composite sandwich structures in marine applications to air explosions highlights a significant gap in our understanding of the dynamic behavior of the curved sandwich structures, which is essential for design improvements. Objective This study aims to explore the dynamic response and failure mechanisms of curved sandwich composite panels subjected to air-blast loading, providing insights into their structural integrity under such conditions. Methods Experiments were performed using laboratory-simulated air shocks generated by a shock tube, employing high-speed photography and digital image correlation to measure deflections on the back surface of the panels. The panels, made with PVC closed-cell foam cores of two densities (H45 and H130), were tested across three curved geometries (radii of 112 mm, 305 mm, and infinity) under various boundary conditions. Results Findings indicate an increase in deformation with a decreased radius of curvature under simple support conditions, a trend that reverses under arrested displacement conditions. Moreover, a reduced radius significantly enhances panel strength and resistance to interfacial damage, with the primary failure mode transitioning from core shear cracking to interfacial debonding as core density increases. Conclusions The study reveals that the radius of curvature, boundary conditions, and core density significantly affect curved sandwich panels’ dynamic response and performance. Panels with smaller radii and higher core densities exhibit increased strength, though boundary conditions introduce variable effects on deformation behavior.

Enhancement of Damping Characteristics through Hybridization: Investigating the Synergistic Effects of Triply Periodic Minimal Surface Additive Metals and Silicone Polymers

Using triply periodic minimal surface (TPMS) metal parts with added silicone polymer can lead to the development of hybrid materials with enhanced damping characteristics. This study aims to develop composite structures by hybridizing additively manufactured TPMS metal parts with added silicone polymers for vibration applications. Central to this investigation is the quest to ascertain the most efficacious damping mechanism. In this context, the finite element method (FEM)‐based model of the primitive TPMS structure, consisting of cobalt–chrome (CoCr) and the concomitant hybrid structure integrated with silicone polymer, is meticulously developed. The damping characteristics of the FEM‐based models are obtained by modal analysis. The models are also validated using experimental modal tests. The findings show a significant improvement in damping characteristics thanks to the hybrid TPMS structure. Specifically, the damping ratios derived from the hybrid TPMS structure exhibit a sixfold increase in time‐domain damping and up to a 30‐fold increase in frequency‐based analysis across two distinct damping calculation methodologies. Overall, this study highlights the potential of additively fabricated primitive TPMS metal parts with added silicone polymer as a promising structure for improving damping properties in various engineering applications.

EXPERIMENTAL AND NUMERICAL STUDY OF INCREASED CORE SURFACE AREA ON THE PERFORMANCE OF ADDITIVELY MANUFACTURED HONEYCOMB SANDWICH STRUCTURES

Abstract Sandwich composite structures have an efficient structural design that provides high bending stiffness and strength at low weight. However, these structures are plagued with weak core-to-facesheet bond strength. In this work, the effect of increasing the contact area between the composite facesheet and honeycomb core was studied. Sandwich panels were manufactured using two different honeycomb structures, a regular and a modified honeycomb, and their respective bond strengths were evaluated using the flatwise tension test (ASTM C297). The honeycombs were additively manufactured using selective laser melting (SLM) process. The modified honeycomb was designed to have a larger surface area while retaining the same relative density as the regular honeycomb. The facesheets were made out of carbon-fiber, while the core was additively manufactured using 304L stainless steel powder. Impact specimens were manufactured and tested for impact resistance. A finite element model was created to study the integrity of the sandwich structures subjected to localized impact damage. The finite element model of the damage resistance due to impact showed a good agreement with the experimental results. Samples with increased contact area showed higher impact resistance. The average impact strength of the modified samples was 41.3% higher than the average impact strength of the regular samples. Flatwise tension results showed that by increasing the contact area between the core and the facesheet the core-to-facesheet bond strength increased.

Mechanical, wear, thermal conductivity and hydrophobicity behavior of Kevlar fiber-epoxy structural composites reinforced with onion peel carbon quantum dot and commercial carbon nanotubes: a comparative study

Mechanical, wear, thermal conductivity and hydrophobicity behavior of Kevlar fiber-epoxy structural composites reinforced with onion peel carbon quantum dot and commercial carbon nanotubes: a comparative study

Frequency-Selective Radar-Absorbing Composites Using Hybrid Core-Shell Spheres.

Radar-absorbing materials (RAMs) covering the exterior surfaces of installed parts and assembled devices are crucial in absorbing most incident electromagnetic (EM) waves. This absorption minimizes reflected energy, thereby enhancing pilot safety and the stability of operating electronic devices without interference. Particularly, active stealth aircraft require effective protection from near- and far-field EM radiation across a wide spectrum of frequencies from both highly integrated electronic components and advanced enemy radars. Studies of RAMs often prioritize absorption over crucial tunability in frequency selectivity, revealing a research gap. In this study, we propose smart RAMs with frequency-selective absorption capabilities. Our approach involves incorporating two types of core-shell spheres in a polymer matrix, which feature shells of either wave-diffuse reflecting metal or wave-absorbing graphene. The key innovation lies in the ability to tailor absorption frequencies in the X-band range (8.2-12.4 GHz) by adjusting the interstitial spaces between the metallic spheres while the scattered waves are efficiently attenuated by graphene networks in the composites. On a metal substrate, a 2 mm-thick composite with an optimized structural composition and ratio of the two types of spheres exhibits a maximum absorption efficiency of 99.3%, effectively trapping and extinguishing incident waves. Combined with the structural tunability and frequency-selective properties of spherical fillers, our approach provides a scalable and effective method for creating functional isotropic coverings on various metallic surfaces.

Reliability and sensitivity analysis of delamination growth of composite laminate structures using two efficient sampling methods

In recent years, composite structures have been used in a large number of applications in aerospace, machinery, marine, and civil engineering. However, there are inevitably many uncertainties in the whole life cycle of composite structures, which can easily lead to structural damage and failure. Therefore, it is important to analyze the reliability and sensitivity of composite structures. At present, most of the contributions use the first-order reliability method (FORM) and the second-order reliability method (SORM) to study the reliability of composite structures and compare them with the results of the Monte Carlo simulation. However, both methods have their limitations. FORM cannot guarantee the calculation accuracy for the highly nonlinear limit state equation, and the calculation efficiency of SORM is too low. Therefore, this paper proposes to use importance sampling (IS) and backpropagation neural network-based Monte Carlo (MC-BPNN) to study the reliability, sensitivity, and dispersion of delamination growth of composite laminates. The results show that compared with FORM and SORM, IS and MC-BPNN have higher calculation accuracy and efficiency and can more accurately evaluate the failure degree of composite structures and ensure their safe operation in the field of aerospace equipment. The universality of this method can make it being widely used in the reliability and sensitivity analysis of different composite materials as well as dispersion analysis.

The dynamic response of composite auxetic re-entrant honeycomb structure subjected to underwater impulsive loading

The researches on dynamic responses of underwater impulsive loading have been conducted. However, the previous study mainly concentrated on metal sandwich structure and fixed supported boundary. The relative research on composite auxetic re-entrant honeycomb structure and simply supported boundary are rarely. In this paper, the effect of the gradient form and relative density on impact resistance performance of composite auxetic re-entrant honeycomb structure was experimentally and numerically investigated. The one-stage light gas gun was applied to provide initial kinetic energy of the fly plate, and the diffuser-type shock tube was utilized to generate and propagate exponential decaying shock wave. The pressure–time curve was respectively amplified and recorded by the charge amplifier and oscilloscope. The response speed, final deflection of rear panel and failure mode of cores and panels were used to evaluate impact resistance of composite auxetic re-entrant honeycomb structures. Moreover, acoustic-structure interaction algorithm was applied to simulate impact course of specimens in Abaqus/Explicit. The results between experiment and numerical simulation exhibited good consistency. The results indicated that the positive gradient form could excessively slow down response speed of rear panel by dissipating energy of shock wave, and the average gradient demonstrated smaller final displacement of rear panel and less failure compared with graded structures.