Search Results (573)

Lightweight polymer composites with effective electromagnetic interference (EMI) shielding are of increasing interest for advanced electronic and aerospace applications; however, conventional glass fiber-reinforced polymers (GFRPs) exhibit inherently low electrical conductivity, limiting their shielding performance. In this study, a hierarchical hybrid conductive architecture was developed by integrating graphene-coated multiaxial glass fiber fabrics with carbon black (CB)-reinforced epoxy matrices to enhance EMI shielding behavior in the X-band (8–12 GHz). Graphene coatings were deposited onto glass fibers via a surfactant-assisted ultrasonic dispersion method, while carbon black (0–1 wt.%) was incorporated into the epoxy matrix using ultrasonication-assisted mixing. Multilayer composites were fabricated using a vacuum bagging process. X-ray diffraction analysis revealed that the composites retained a predominantly amorphous epoxy/glass fiber matrix while exhibiting broad carbon-related diffraction features associated with disordered graphitic domains. Electrical conductivity measurements indicated that all composites remained in the insulating regime (~10⁻⁹ S/m), suggesting that a fully interconnected conductive network was not established within the investigated filler range. Despite the absence of a continuous conductive network, measurable EMI shielding performance was achieved. The composite containing 0.25 wt.% CB exhibited the highest shielding effectiveness, reaching approximately 12 dB at ~11.2 GHz. Analysis of the shielding contributions showed that absorption contributions (SEA) were consistently higher than reflection contributions (SER) across the studied frequency range. Morphological observations revealed that well-dispersed CB at low loading facilitated the formation of localized conductive domains that may contribute to tunneling-assisted polarization and interfacial charge accumulation. At higher CB contents, particle agglomeration reduced dispersion quality and limited effective pathway formation, while dynamic mechanical analysis indicated enhanced stiffness at low CB loading. FTIR results confirmed the absence of new chemical bonding, indicating that CB acts as a physically dispersed conductive filler. Overall, the results show that effective EMI shielding can be achieved in electrically insulating composites through the combined effect of hierarchical structural design and localized conductive features. This approach provides a practical pathway for developing lightweight EMI shielding materials with controlled filler loading and preserved structural integrity for aerospace and electronic applications. Full article

(1) Background: Provisional restorations play a crucial role in maintaining oral function and must exhibit adequate mechanical properties, particularly fracture resistance, to ensure structural integrity throughout the provisional phase. The aim of this study was to compare the flexural strength and modulus of materials used for provisional dental prostheses, with and without fiber or metal reinforcement. (2) Methods: Standardized specimens (2 × 2 × 25 mm) were fabricated from an acrylic resin (Unifast LC), a 3D-printed resin (NextDent C&B), and a bis-acryl resin (Luxatemp Fluorescence). For each material, four experimental subgroups were established: no reinforcement, two types of glass fiber reinforcement (EverStick C&B and EverStick Post NET), and metal reinforcement. Specimens were subjected to a three-point bending test. Flexural strength and flexural modulus were analyzed using a two-way, non-parametric ANOVA with the aligned rank transform. The significance level was set at 0.05. (3) Results: Material type and reinforcement strategy significantly affected flexural strength and flexural modulus. Fiber reinforcement with EverStick C&B yielded the highest values across all materials, particularly in the acrylic resin. Metal reinforcement showed moderate improvements, whereas EverStick NET had limited or no effect and reduced strength in the bis-acryl resin. Reinforced specimens exhibited altered fracture behavior, preventing complete separation after failure. (4) Conclusions: Fiber reinforcement, particularly with EverStick C&B, significantly enhances the flexural strength and modulus of provisional materials. The reinforcement performance is dependent on its type and material interaction, modifying fracture behavior by preventing complete separation. Full article

The spatial organization of microscale fillers is critical for macroscopic performance, yet precise control over their distribution and orientation remains a major challenge in direct ink writing. Here, we present an acoustofluidic capillary nozzle that integrates acoustic manipulation into direct ink writing, enabling programmable in situ assembly of functional fillers during extrusion. By coupling a piezoelectric transducer with a commercial glass capillary, stable acoustic standing waves are established within the flow channel, driving suspended filler particles toward pressure nodes via acoustic radiation forces. Simulations and experiments systematically investigate how capillary geometry and material properties influence acoustic energy distribution and particle assembly behavior. In particular, rectangular capillaries generate stable multi-node standing waves, inducing periodic alignment of nickel-coated carbon fibers into ordered conductive bundles. This acoustically programmed microstructure reduces the percolation threshold from 8 wt% to 2 wt% and enhances electrical conductivity by up to 32.1-fold at identical filler contents. Meanwhile, the composites exhibit pronounced anisotropic conductivity and maintain excellent mechanical flexibility, with stable electromechanical performance under 16% bending strain and cyclic loading. This work demonstrates a simple and scalable acoustofluidic nozzle platform for programmable microstructure engineering in direct ink writing, offering new opportunities for fabricating high-performance multifunctional composites. Full article

The reprocessing of wood–plastic composites (WPCs) significantly affects their structural integrity and thermal behavior. Despite this, the effect of reprocessing on PVC-based WPCs has not been extensively investigated, and the mechanism is not well understood. This study evaluated the effect of reprocessing on the properties of a PVC-based WPC. Small pieces of extruded WPC boards (2–4 mesh) were first milled to a granulation of 50 mesh, and then the material was reprocessed by compression molding, with part of the samples reinforced with glass- and carbon-fiber fabric. The physical and mechanical properties of the reprocessed material were analyzed, and the chemical and thermal characteristics of the reprocessed WPC were compared with the virgin WPC. The results of the mechanical and physical property tests showed that the reprocessed WPC had satisfactory properties compared with the virgin WPC. Samples reinforced with carbon-fiber fabric showed a statistically significant increase in tensile and flexural strength in comparison with unreinforced reprocessed WPC samples. Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) showed that partial dehydrochlorination, thermal degradation and a decrease in thermal stability occurred. Overall, the results of this study show that although chemical degradation and a decrease in thermal stability were present in the reprocessed WPC, it retained satisfactory mechanical and physical properties that could be improved by reinforcing it with carbon-fiber fabric. Full article

To date, lithium–ion batteries (LIBs) are considered one of the most promising and market-leading energy storage systems due to their high theoretical capacity and energy density. However, poor thermal and cyclic stability, low electrolyte uptake, and the possibility for frequent short circuits of typical separators and evolution of several gases during long cycle operation pose several problems for LIBs. Metal-organic frameworks (MOFs) have attracted widespread interest as a promising material for improving the cycle stability and safety of rechargeable batteries due to their inherent surface and structural properties such as high specific surface area, high porosity, and ionic conductivity. In this work, the aim is to provide detailed descriptions of the synthesis routes and parameters for obtaining various MOFs such as Zr-MOF-808 and Ni-MOF-74 nanoparticles and the fabrication of those MOF-integrated separators. To optimize the crystallinity, morphological and compositional characteristics, and several material characterizations such as XRD, SEM, and EDX have been applied. Afterwards, the synthesized MOF-integrated glass fiber (GF) separators have been developed for lithium–ion battery (LIB) applications. To investigate the electrochemical performance and the effect of MOF integration into the separators, electrochemical studies in the form of galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopy (EIS) have been evaluated by preparing CR2032-type half-coin cells. This MOFs-integrated GF-separators and synthesized LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) cathode materials-based coin cell LIB exhibited higher cycle stability than bare GF-separator based LIB. This novel approach and extensive research suggest that development of MOF-integrated separators could significantly improve cycle stability by reducing the internal cell degradation for next generation energy storage devices. Full article

There is a lack of knowledge concerning the interlaminar fracture toughness of 3D-printed composite materials using both commercial filament composites and fused deposition modeling (FDM) technology from Markforged^®. In this investigation, additive manufacturing (AM) continuous fiber-reinforced thermoplastic (cFRT) specimens have been tested to characterize the initiation and propagation of interlaminar fracture toughness in mode I (G_I). Unidirectional glass fiber (GF)-reinforced polyamide 6 (PA) laminates were characterized by means of the double cantilever beam (DCB) test. These specimens were manufactured using a MarkTwo^® printer and tested without doublers, following a laminate configuration selected according to appropriate experimental findings reported in the state of the art, ensuring reliable fracture characterization. The experimental results exhibited repeatability and strong agreement between the modified compliance calibration (MCC) and modified beam theory (MBT) reduction methods. The resistance curve (R-curve) indicated a progressive increase in fracture resistance during crack propagation. To analyze the experienced failure mechanism during testing, the fracture surfaces of representative post-mortem DCB specimens were observed using a scanning electron microscope (SEM), revealing characteristic morphological features at two magnification levels. Moreover, representative cross-sections of the tested DCB specimens were electronically observed to analyze the interlaminar morphologies, showing an irregular and random distribution of the matrix, fiber, and voids between consecutive plies and adjacent deposited rasters. Compared with previously reported Markforged^® continuous fiber-reinforced systems, the GF/PA composite material exhibited intermediate initiation fracture toughness but lower propagation toughness. This study contributes to filling the existing gap in fracture toughness data for glass fiber-reinforced additively manufactured composites. Full article

Pultrusion is an efficient continuous manufacturing process for fiber-reinforced polymer (FRP) composites, but conventional open-bath impregnation has limitations such as resin exposure, quality variation, and resin loss. To overcome these limitations, closed-injection pultrusion (CIP) and short-pot-life resin systems have recently been introduced. However, the effects of processing variables on the quality and properties of composites manufactured using such resin systems have not been fully clarified. In this study, the effects of resin viscosity and pulling speed on the quality and mechanical properties of carbon FRP (CFRP) and glass FRP (GFRP) composites manufactured by CIP were investigated. CFRP and GFRP composites were fabricated at resin temperatures of 30 and 40 °C and pulling speeds of 300, 400, and 500 mm/min. The manufactured composites were evaluated in terms of void content, microstructure, hardness, and tensile properties. The results showed that increasing pulling speed increased void content and promoted macrovoids and locally poor impregnation, whereas the influence of resin temperature was relatively limited. Hardness, tensile strength, and elastic modulus decreased as pulling speed increased. These results demonstrate that CFRP and GFRP composites can be successfully manufactured by CIP using short-pot-life resin systems, and that precise control of resin viscosity and pulling speed is essential for achieving high quality and mechanical performance. Full article

This study experimentally investigates the structural behavior of hexagonal- and square-shaped composite specimens subjected to vertical compression, vertical tension, and diagonal tension loading. The specimens were fabricated using four- and six-layer alkali-resistant (AR) glass textile reinforcements embedded in a modified cementitious mortar via pull, pour, and roll manufacturing techniques. The mechanical performance of polyvinyl alcohol (PVA) fiber-reinforced composite connectors and steel clamp-type elements was also evaluated at the joints of hexagonal specimens under vertical tension and lateral shear loading. The results show that increasing the number of textile layers significantly enhances structural performance. A 50% increase in textile layers improved load-carrying capacity by up to 56% in compression, 104% in tension, and 216% in diagonal tension. Corresponding increases of approximately 20–42% in ductility and up to 266% in energy dissipation capacity were observed. No failure occurred in the connecting elements, confirming their adequate stiffness, strength, and ductility. In addition, validated three-dimensional finite element models were developed to simulate the response of the hexagonal specimens. Overall, the proposed system demonstrates strong potential for applications such as infill walls, cladding, and sandwich panels due to its favorable strength, ductility, and energy absorption capacity. Full article

We present a vacuum-assisted Polymethyl methacrylate (PMMA) impregnation process for cotton textiles, coupled with a physics-aware bidirectional artificial neural network (ANN) framework, to both predict and tune the natural fiber composite response from a compliant and flexible to a stiff and strong behavior. Cotton fabric samples were impregnated with acetone-borne PMMA baths, ranging from 0 to 5 wt.% polymer concentration. After drying, the PMMA formed conformal fiber coatings and inter-fiber bridges, with optimal load transfer observed at approximately 0.5–1.0 wt.%. Mechanical properties, including the elastic modulus, tensile strength, ductility, and toughness, were measured alongside Differential Scanning Calorimetry (DSC), Glass Transition Temperature (T_g), Change in heat capacity at constant pressure (ΔCp), gravimetry, and morphology tests. Rule-of-mixtures, porosity, and thermal constraints were embedded as regularization within the ANN loss functions to improve the physical consistency of the training. The forward and inverse models achieved sub-percent prediction errors with narrow bootstrap confidence intervals. It was found that removing physics regularization notably increases forward model error (by fivefold), as well as the inverse model error by one order of magnitude. Full article

The purpose of this study was to use the finite element analysis method to determine the influence of framework material on stresses in different parts of a model of an All-on-4 prosthesis supported by bendable monoblock implants. A three-dimensional solid model of an edentulous mandible was reconstructed from computed tomography data and segmented using 3DSlicer. Four bendable monoblock implants were positioned in accordance with the All-on-4 configuration. Screw-retained prostheses were modeled with the framework considered fabricated using one of five materials. These were cobalt–chromium (Co-Cr) alloy, titanium (Ti) alloy, polyetheretherketone (PEEK), polyetherketoneketone (PEKK), and a glass fiber-reinforced polymer composite (FRC) material. Four types of clinically relevant loads (300 N) were applied statically, namely, unilateral oblique, unilateral vertical, bilateral oblique, and bilateral vertical. Maximum and minimum principal stresses were determined in the cortical bone, and maximum von Mises stress was determined in each of the other parts of the model. Across most loading conditions, PEEK and PEKK showed higher stress values in the cortical bone and in the implants. In the screws, PEEK and PEKK also showed higher stress values, except in the anterior implant screws under bilateral loading conditions. In the framework, the highest stresses were obtained when a metal was the material of fabrication. Across all loading conditions, with FRC, the stress transfer was balanced. Thus, the prevent results suggest that FRC may be a suitable alternative to metallic materials for fabricating the framework of an All-on-4 prosthesis supported by bendable monoblock implants. Full article

The demand for lower-impact materials in mobility has increased interest in the lightweight composite structures for electric vehicles (EVs). This study presents an extended and revised dataset for biaxial non-crimp fabric (NCF) composite laminates intended for two-wheeled EV chassis applications, building on earlier published results by repeating all mechanical tests and recalculations and by adding a full stress–strain analysis, a repeatability assessment across multiple specimens, and a digital image correlation (DIC)-based strain evaluation. Three material families, represented by four laminate conditions, were investigated: carbon/epoxy composites post-cured for 4 h and 10 h, glass-fiber composites, and linen (flax) composites. The tensile and flexural behaviors were characterized according to ISO 527-4 and ISO 14125, respectively, while a GOM ARAMIS optical system was used to obtain the axial strain, transverse strain, and Poisson’s ratio. Carbon laminates showed the highest performance, with the 10 h post-cure condition reaching 1126 MPa tensile strength, up to 60 GPa Young’s modulus, 696 MPa flexural strength, and 43 GPa flexural modulus. Glass laminates provided intermediate properties, whereas flax laminates showed lower strength but higher compliance and deformation capacity. The obtained results show that the biaxial NCF composites studied in this work offer weight-saving potential for micro-mobility chassis and provide a standard-based benchmark for future durability and life-cycle studies. Full article

Facing the increasingly severe energy challenges and environmental problems, the development of thermally stable, lightweight, and thermal insulating materials is critical. Herein, we report an organic-inorganic composite strategy combined with a high-temperature carbonization step to fabricate aerogel-containing composites synergistically reinforced with chopped glass fibers and hollow glass microspheres. By systematically varying the ratio of acrylic emulsion to potassium silicate solution, we investigated the effects on the forming behavior, microstructure, hydrophobicity, thermal stability, and thermal insulation performance. Increasing the acrylic emulsion fraction substantially enhanced hydrophobicity, yielding a maximum water contact angle of 129.3°. Concurrently, the apparent density decreased from 0.18 g/cm³ to 0.09 g/cm³ and the thermal conductivity dropped from 57.9 mW/(m·K) to 29.0 mW/(m·K). Mechanical testing revealed that the compressive Young’s modulus decreased with increasing acrylic content, from 3.6 MPa for the purely inorganic sample to 0.55 MPa at 70% acrylic content, reflecting a trade-off between stiffness and organic-derived porosity. Microstructural characterization revealed a hierarchical porous network in which uniformly dispersed hollow glass microspheres and the aerogel-derived silica network form an efficient thermal barrier system. Thermogravimetric analysis demonstrated excellent thermal stability, with total weight loss below 5% up to 800 °C. Infrared thermography analysis showed that, after unilateral heating at 300 °C and 400 °C for 10 min, the backside surface temperature of the composites decreased as the acrylic emulsion content increased. At 300 °C, the temperature decreased from 176.1 °C for AP-1 to 151.0 °C for AP-4, while at 400 °C, it decreased from 228.5 °C to 199.3 °C. These results indicate that the composites exhibit effective thermal insulation and maintain structural stability under high-temperature exposure. Taken together, this facile and scalable approach yields these aerogel-containing composites that combine low density, low thermal conductivity, robust structural integrity, and good environmental resistance, as evidenced by a water contact angle of 129.3°, making them promising candidates for aerospace, building, and industrial high-temperature insulation applications. Full article

Textile-reinforced concrete (TRC) beams have attracted widespread interest in recent years as an alternative to fiber-reinforced polymer (FRP) techniques. However, despite their effectiveness, they are often associated with high material cost, sensitivity to elevated temperatures, and limitations in bonding performance under certain environmental and surface conditions. This research examines incorporating textile reinforcement internally (INT) by supplementing steel bars with glass fiber grids, as well as externally (EXT) by retrofitting existing members. The experimental work evaluates five RC beams: a control (CTR), two INT beams strengthened with alkali-resistant glass fabric textile (AR-GFT), one using one layer (INT1L) and the other three layers (INT3L), and two EXT beams where AR-GFT is bonded with mortar, again with one layer (EXT1L) and three layers (EXT3L). Altogether, 10 beams were tested, with duplicate specimens for every configuration. Observing load-deflection responses, cracking behavior, and the strengthening system’s performance revealed that AR-GFT contributes to enhanced load-bearing resistance in the RC beams. The INT1L beams exhibited negligible improvement compared with the CTR specimen, suggesting that internal strengthening alone does not meaningfully increase strength. Conversely, the INT3L beams demonstrated a 45% rise in strength for one sample, although the second performed similarly to the CTR specimen owing to slippage between the textile and adjacent matrix. EXT3L beams achieved up to a 90% increase in load-bearing capacity in one specimen. Nevertheless, the second specimen exhibited textile layer debonding and performed similarly to the CTR beam, underlining the necessity for correct textile positioning and sufficient mortar impregnation during application. Moreover, a three-dimensional (3D) nonlinear finite-element analysis (FEA) was performed to replicate beam responses, showing strong correlation with experimental observations. Overall, the results indicate that textile-based strengthening systems can successfully retrofit and upgrade RC structures, provided meticulous attention is paid to the quality and execution of the installation process. The study provides new insights into the flexural behavior of textile-strengthened RC beams, particularly in terms of the interaction between internal and external textile reinforcement with conventional steel. Full article

This study investigates the catalytic activity and surface behaviors of V₂O₅ catalysts modified with promoter components to improve low-temperature activity and suppress SO₂-to-SO₃ oxidation. Moreover, we fabricated corrugated-type catalysts using glass fiber sheets as substrates, because powdered catalysts revealed limitations for practical applications. The modified catalysts were prepared via a slurry mixing method using vanadium precursor with different promoters such as W, Nb, Zr, Mo, Ce, Fe supported on TiO₂. The catalysts were fabricated into slurry coating type catalysts using glass fiber sheets and the catalytic activity, specific surface area, and acid sites were investigated. The performance of corrugated-type catalyst and oxidation of SO₂ to SO₃ over a wide temperature range were evaluated using a Micro-Reactor. Our results showed that adding a promoter improves the catalytic performance of VW/Ti catalysts by enhancing surface acidity. The results varied depending on the catalyst loading and promoter components over a wide temperature range. Among them, VWNb/Ti catalysts exhibited the highest NOx conversion of 80.9% at 350 °C despite the high gaseous velocity (AV of 51 m·h⁻¹) and the large flow rate of 20 L·min⁻¹, with the lowest Ea of 13.7 kJ·mol⁻¹. Among the evaluated promoters, Nb exhibited the most favorable balance of activity and SO₂-to-SO₃ oxidation. These results suggest that the Nb modification strategy can be extended to commercial SCR catalysts, providing a practical approach for improving catalytic performance. Full article

Air pollution has drawn increasing attention. The channel-type structure, as an ideal energy-saving and resistance-reducing strategy for air filters, can effectively lower filtration resistance. However, current commercial channel-type filters generally exhibit only medium or low filtration efficiency, and the use of plant fibers as raw material limits their application in high-efficiency filters. In this study, high-efficiency glass fiber filter paper was combined with a channel-type structure, and the formulation and processing techniques suitable for the channel-type design were systematically investigated, leading to the fabrication of channel-type high-efficiency filters. The optimal formulation was determined to be a blend of glass wool fibers and 6 mm Tencel fibers in a 6:4 ratio, coated with a thermosetting resin, which yielded filter paper suitable for wave-pleating. The resulting filter paper demonstrated a filtration efficiency of 99.9624%, a pressure drop of 265.6 Pa, and a pleat aspect ratio of 0.209. Using this formulation, pilot-scale filter paper was produced and wave-pleated under processing conditions including a roller speed of 5 m/min, a roller gap of 0.4 mm, and a roller temperature of 160 °C, which was then used to fabricate channel-type high-efficiency filters. The finished channel-type filters achieved a filtration efficiency of 99.9940% with a pressure drop of 164.0 Pa. Compared to traditional pleated filters of the same volume and efficiency rating, the channel-type filter exhibited a 49.53% larger filtration area, a 33.13% lower face velocity, and a 31.67% reduction in pressure drop. This work offers a novel approach to reducing resistance and enhancing efficiency in air filtration systems. Full article