Search Results (752)

This study describes a novel approach using fibrous Al₂O₃-Nylon 6 composites to induce inhibition behavior in silica scaling systems. The composite fibers were fabricated with a wet-spinning process using the coagulation of a methanolic Nylon-CaCl₂ solution with Al₂O₃ powder after immersing the thread-like solution in water. The mesoporous nylon fibers composed of Al₂O₃ powders ranging from 10 to 30 wt% loading demonstrated superior adsorption capabilities to silica in water, behaving with the Freundlich model and exhibiting effective multilayer adsorption onto the Al₂O₃ sites embedded in the fiber. Furthermore, the composite fibers inhibited silica scaling, even at high concentrations, due to a substantially efficient reduction in soluble silica when the composite fiber was present in the system. The utilization of 15 g of composite fibers resulted in a rapid drop to approximately 30 mg/L within the initial 10 h, which is a considerable improvement compared to the 300 mg/L observed in the fiber-free control sample. Notably, the presence of an elevated fiber content exceeding 7.5 g demonstrated the complete inhibition of silica precipitation. An analysis of the pore volume using nitrogen adsorption experiments before and after silica adsorption showed that silica adsorption resulted in a significant decrease in mesoporous properties at the alumina sites. This indicated an efficient adsorption of silica onto the alumina site, effectively removing silica from the system. Full article

In this study, comprehensive analyses were used to evaluate the physical and chemical properties of basalt fibers, employing a variety of instruments. Additionally, heat treatment and solvent treatment methods were used to eliminate the sizing present on fiber surfaces. The heat treatment process involved determining the optimal temperature and duration required to remove the sizing from the basalt fibers. The appearance, chemical composition, and crystal structure of the original fibers were examined, including those subjected to heat treatment and those treated with solvents. These treated fibers were then incorporated into concrete to create basalt fiber-reinforced concrete (BFRC) specimens for mechanical tests, which assessed their compressive, flexural, and splitting tensile strengths. The results revealed that heat treatment at 300 °C for 180 min effectively removed the sizing on the basalt fibers, and the heat-treated basalt fibers exhibited uniform dispersion inside the BFRC specimens. In addition, solvent treatment primarily removed the soluble components of the sizing. The mechanical properties of specimens with sizing-removed basalt fibers were better than the specimens with original basalt fibers and the benchmark specimens. Crucially, the mechanical test results demonstrated that BFRC incorporating heat-treated basalt fibers exhibited a superior mechanical performance compared to BFRC incorporating original fibers or fibers subjected to the solvent treatment. Full article

A balance between model complexity, accuracy, and computational cost is a central concern in numerical simulations. In particular, for stochastic fiber networks, the non-affine deformation of fibers, related non-linear geometric features due to large global deformation, and size effects can significantly affect the accuracy of the computer experiment outputs and increase the computational cost. In this work, we systematically investigate methodological aspects of fiber network simulations with a focus on the output accuracy and computational cost in models with cellular (Voronoi) and fibrous (Mikado) network architecture. We study both p and h-refinement of the discretizations in finite element solution procedure, with uniform and length-based adaptive h-refinement strategies. The analysis is conducted for linear elastic and viscoelastic constitutive behavior of the fibers, as well as for networks with initially straight and crimped fibers. With relative error as the determining criterion, we provide recommendations for mesh refinement, comment on the necessity of multiple realizations, and give an overview of associated computational cost that will serve as guidance toward minimizing the computational cost while maintaining a desired level of solution accuracy. Full article

The growing pollution of the environment with slowly decomposing waste, as well as the increasing drug resistance of pathogens, including the antibiotic resistance of bacteria, has led to a search for new solutions based on biodegradable and natural materials, which are known for their potential bacteriostatic properties. This study aimed to produce nanofibers by blowing from a polylactide (PLA) polymer solution containing natural compounds (e.g., beeswax, propolis). As a result of the conducted research, nanofibers were produced from PLA solutions containing various additives. The fibers’ mean diameter ranges from 0.36 to 2.38 µm, depending on the process parameters. To the authors’ knowledge, fibers were produced for the first time by blow spinning from a polymer solution containing propolis and beeswax. Full article

The utilization and incorporation of glass fiber-reinforced plastics (GFRP) in structural applications and architectural constructions are progressively gaining prominence. Therefore, this paper experimentally and numerically investigates the use of GFRP I-beams in conjunction with concrete slabs to form composite beams. The experimental design incorporated 2600 mm long GFRP I-beams which were connected compositely to concrete slabs with a 500 mm width and 80 mm thickness. The concrete slabs are categorized into two groups: concrete slabs cast using normal-strength concrete (NSC), and concrete slabs prepared using high-strength concrete (HSC). Various parameters like the type of concrete (normal and high-strength concrete), type of stiffeners bonded to the composite section (bolt–epoxy or bolt only), and inclusion of corrugated metal sheets were investigated. To obtain the full shear connection between the GFRP I-sections and concrete slabs, two rows of shear connectors in the form of bolts were utilized. These shear connectors were erected to the top flange of the GFRP I-sections to compositely connect between the GFRP I-beams and the concrete slabs as well as the corrugated metal sheets. The strengthening of the shear webs of GFRP I-beams with GFRP T-section stiffeners resulted in an enhancement in the flexural and shear strength. The failure loads in the case of the bolt–epoxy connection for the stiffeners were 8.2% and 10.0% higher than those in the case of bolt only when the concrete compressive strengths were 20.1 MPa and 52.3 MPa, respectively. Moreover, the effect of the concrete compressive strength was vital where the failure loads increased by 79.9% and 77.1% when HSC was used instead of NSC for the cases of bolt–epoxy and bolt only, respectively. The epoxy adhesive used in conjunction with mechanical connectors, specifically bolts, resulted in sufficient composite action and delayed shear failure within the web of the GFRP beam. For the specimens with bolt–epoxy connection, strain levels in the concrete slabs were consistently higher than in the other specimens with bolts alone at the same loading level. The concrete slabs integrated with HSC registered strain levels that were 20.0% and 21.8% greater for bolt–epoxy and bolt-only connections, respectively, when compared to those using normal-strength concrete (NSC). This discrepancy can likely be credited to the enhanced composite interaction between the concrete slabs and the GFRP I-beams. In addition, ABAQUS software (version 6.2) was used to develop FE models to analyze the tested composite beams and provide a parametric study using the verified models. Full article

In this work, the adhesion behavior of chemically treated banana and coir Colombian fibers embedded in polylactic acid (PLA) and unsaturated polyester resin (UPR) matrices was investigated. Both types of fibers were treated with a 5 wt.% sodium hydroxide solution for one hour. The properties of treated and untreated fibers were determined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and tensile tests. To evaluate the adhesion behavior of the fibers in PLA and UPR matrices, pull-out tests were performed, and the percentage of broken fibers was determined. The results showed that alkaline treatment improved the fibers’ physicochemical, mechanical, and thermal properties. In addition, the alkaline treatment was able to improve the adhesion behavior of coir and banana fibers to PLA and UPR matrices. The banana fibers showed a percentage of broken fibers of 100%, while the coir fibers showed a slight increase in IFSS value. This behavior is attributed to the improvement in surface roughness due to the removal of non-cellulosic composites and impurities. Full article

Wood and plants are made of fibers that contain, in addition to cellulose, lignin and hemicelluloses. Xylan and galactoglucomannan are the dominant secondary cell wall hemicelluloses. In modern times, fibers are important materials for the biorefinery industry and for developing biocomposites. For these and other applications, the structural analysis of fibers is important, and Raman spectroscopy is among the many analytical techniques used. However, given the structural similarity between hemicelluloses and cellulose, many of their Raman contributions overlap, and the extent to which the overlapping features of hemicellulose modify the spectrum of cellulose is not yet fully understood. The present investigation focuses on this aspect by examining xylan, one of the hemicelluloses. As a model system, samples with various mass ratios of cotton microcrystalline cellulose (MCC) and xylan (birch wood) were prepared and analyzed using FT-Raman spectroscopy. In most cases, the Raman intensities were sample-composition-dependent, and, when the selected band intensities were plotted against the xylan content, good linear correlations (with an R² between 0.69 and 1.0) were obtained. The results indicated that with increased xylan content, the peak intensities increased at 1460, 898, and 494 cm⁻¹ and declined at 1480, 1121, 1096, and 520 cm⁻¹. Additionally, intensity changes (%) in the MCC bands with respect to MCC’s fractions in various mixture samples showed that, in most cases, the mixture intensities increased and were highly correlated with the xylan amounts in the mixtures (with an R² between 0.75 and 0.97). These findings were applied to interpret Raman spectra of selected xylan-containing delignified plant fibers. It is hoped that the insights gained in this study will allow for better interpretation of the spectra of natural and treated plant materials. Full article

Theoretical modeling calculations and experimental measurements were adopted to investigate the oxygen activation effect of carbon nanofibers (CNFs) interacting with polypyrrole (PPY). The CNF undergoes a hydrothermal oxidation process to form epoxy and hydroxyl groups containing carbon nanofibers (CNF-O). The oxygen activation effect of CNF on the electronic and electrochemical properties was investigated through the interfacial interaction between CNF-O and PPY. Theoretical modeling calculation discloses that CNF-O/PPY exhibits lower electronic bandgaps (0.64 eV), a higher density of states (10.039 states/eV), and a lower HOMO–LUMO molecular orbital energy gap (0.077 eV) than CNF/PPY (1.56 eV, 7.946 states/eV and 0.112 eV), presenting its superior electronic conductivity and electroactivity. The Mulliken population and charge density difference analysis disclose the stronger interface interaction of CNF-O/PPY caused by epoxy and hydroxyl groups. Cyclic voltammogram measurements reveal that CNF-O/PPY exhibits a higher response current and a higher specific capacitance (221.1–112.2 mF g⁻¹) than CNF/PPY (57.6–24.2 mF g⁻¹) at scan rates of 5–200 mV s⁻¹. Electrochemical impendence spectrum measurements disclose that CNF-O/PPY exhibits a lower charge transfer resistance (0.097 Ω), a lower ohmic resistance (0.336 Ω), a lower Warburg impedance (317 Ω), and a higher double-layer capacitance (0.113 mF) than CNF/PPY (1.419 Ω, 9.668 Ω, 7865 Ω, and 0.015 mF). Both theoretical and experimental investigations prove that CNF-O/PPY presents an intensified intermolecular interaction rather than CNF/PPY. The promotive oxygen activation effect of CNF could contribute to improving the electronic and electrochemical properties of CNF-O/PPY. Full article

This paper presents an innovative flexural repair technique for pre-damaged reinforced concrete T-beams using eco-friendly steel-fibre-reinforced geopolymer concrete (SFRGPC). The study considers various parameters such as repair layer depth, location and configuration, and the use of additional reinforcement in one beam. The beams were preloaded to 50% of their ultimate flexural capacity. Extensive measurements were taken, including crack initiation and propagation, crack width, initial stiffness, load deflection, peak loads, ductility index, and strain values. The structural performance of the repaired T-beams under flexural loading was predicted using an analytical model. The repaired beams showed an increase in carrying capacity, stiffness, and ductility, but the failure mode was identical to the control samples. The study shows that SFRGPC shows great promise as a technique for not only repairing pre-damaged reinforced concrete beams but also for their strengthening. The best results were obtained with three-sided jackets with fibrous geopolymer concrete only, resulting in a load-carrying capacity increase of 25.8% compared to reference T-beams. The bonding between SFRGPC and existing concrete was effective, with no slippage or disintegration at the interface. The repaired beams’ structural behaviour and performance under flexural loads were successfully predicted using the analytical model, with a precision of about 98%. Full article

In the pulp and paper industry, pulp testing is typically a labor-intensive process performed on hand-made laboratory sheets. Online quality control by automated image analysis and machine learning (ML) could provide a consistent, fast and cost-efficient alternative. In this study, four different supervised ML techniques—Lasso regression, support vector machine (SVM), feed-forward neural networks (FFNN), and recurrent neural networks (RNN)—were applied to fiber data obtained from fiber suspension micrographs analyzed by two separate image analysis software. With the built-in software of a commercial fiber analyzer optimized for speed, the maximum accuracy of 81% was achieved using the FFNN algorithm with Yeo–Johnson preprocessing. With an in-house algorithm adapted for ML by an extended set of particle attributes, a maximum accuracy of 96% was achieved with Lasso regression. A parameter capturing the average intensity of the particle in the micrograph, only available from the latter software, has a particularly strong predictive capability. The high accuracy and sensitivity of the ML results indicate that such a strategy could be very useful for quality control of fiber dispersions. Full article

The cracking of cementitious materials due to their quasi-brittle behavior is a major concern leading to a loss in strength and durability. To limit crack growth, researchers have incorporated microfibers in concrete mixes. The objective of this study is to determine if nano-reinforcements can arrest cracks and enhance the material performance in comparison to microfibers. A total of 28 specimens were prepared to investigate and compare the effects of incorporating carbon nanotubes (CNTs) as a nano-reinforcement and polyethylene (PE) fibers at a macro-level and their combination. Compressive and flexural strengths were experimentally tested to assess the mechanical performance. The microstructure of the mortar samples was also examined using a scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX). The ductility increased by almost 50% upon the addition of CNTs, while no significant enhancement was witnessed for the compressive strength. The flexural strength increased by 169% and the flexural strain by 389% through the addition of the combination of CNTs and PE fibers. Full article

Increasing amounts of waste resulting from over-consumption carry substantial risks for human and environmental health, and disposing of this waste requires enormous amounts of energy. As a result, waste-to-wealth and circular economy approaches have gained attention in both academia and the commercial sector in recent years. Accordingly, this study aims to develop electromagnetic shielding materials by converting non-conductive waste textiles into conductive value-added product and porous fabrics by carbonizing the structure itself rather than by adding any conductive particles. To this end, the novel contribution of the present study is that waste textiles were converted into activated carbon in a shorter time and without compromising the integrity of the fibrous network via microwave pyrolysis without inert gas. Sulfuric acid was used as a dehydration and activation agent, suppressing the release of volatile organic substances and eliminating greenhouse gas emissions. This approach also increased product yield and reduced energy consumption and sample shrinkage. The structures of the activated carbon textile showed EMI shielding within 20–30 dB (99.9% attenuation) in the 1–6 GHz frequency range. The maximum SSE/t value of 950.71 dB·cm²·g⁻¹ was obtained with the microwave post-treated activated carbon textile. Micropores were dominant characteristics of these materials, and pore diameters increased with increased acid concentration. The maximum surface area of 383.92 m²/g was obtained with 8% acid. Ultrasound treatment reduced water-energy consumption and cost. Only 5 min of microwave post-treatment increased textile conductivity and thermal stability and contributed positively to electromagnetic shielding. Full article

The 3D printing process is different from traditional construction methods of formwork casting due to the use of additive manufacturing. This study develops a suitable 3D-printed carbon fiber-reinforced cement mortar (CFRCM) considering the extrudability, fluidity, setting time, and buildability of the CFRCM. The difference in compressive strength and flexural strength between 3D-printed specimens and conventional cast specimens was investigated by varying the amount of carbon fiber added (carbon fiber to cement ratio, 2.5 vol.‰, 5 vol.‰, 7.5 vol.‰, and 10 vol.‰) and the curing times (7th day and 28th day). The results of the experiments indicate that the addition of 6 wt.% cement accelerators to the cementitious mortar allows for a controlled initial setting time of approximately half an hour. The fluidity of the CFRCM was controlled by adjusting the dosage of the superplasticizer. When the slump was in the range of 150 mm to 190 mm, the carbon fiber to cement ratio 2.5 vol.‰ could be incorporated into the cementitious mortar, enabling the printing of hollow cylinders with a height of up to 750 mm. Comparing the 3D-printed specimens with the traditionally cast specimens, it was found that the addition of a carbon fiber to cement ratio of 7.5 vol.‰, and 10 vol.‰ resulted in the optimal compressive strength and flexural strength, respectively. Full article

The potential for sustainable lignocellulosic agro-waste is immense, owing to the fact that it represents the most abundant organic compound on Earth. It is a valuable and desirable source for material production across numerous industries due to its abundance, renewability, and biodegradability. This paper explores the world of barley fibers, which are extracted from the straw of two different cultivars (old Rex or new Barun) and have tremendous potential for use, primarily for technical textiles. The quantity of the extracted fibers depends both on the type of barley used and on climate conditions that influence the plants’ growth, resulting in fiber yields ranging from 14.82% to 19.59%. The chemical composition of isolated fibers revealed an optimal content of cellulose and lignin in barley fibers isolated from the Rex variety. Those results were confirmed with FTIR analysis, which revealed a lower intensity of peaks associated with hemicellulose and lignin and, therefore, indicated their better removal after the chemical maceration process. In terms of fiber density, the quality of the fibers was comparable to that of cotton fibers, but they differed significantly in moisture regain (10.37–11.01%), which was higher. Furthermore, sufficient fiber tenacity (20.31–23.08 cN/tex) was obtained in a case of old-variety Rex, indicating the possibility of spinning those fibers into yarns, followed by their extended usage for apparel. Additionally, our paper reveals the possibility of fulfilling the requirements of the zero waste principle due to the fact that a high percentage of solid waste left after the fiber extraction (26.3–32.3%) was afterwards successfully used for the production of biofuels, enabling the closing of the loop in a circular economy. Full article

Easy maintenance and high durability are expected in structures made with fiber-reinforced cementitious composite (FRCC) reinforced with fiber-reinforced polymer (FRP) bars. In this study, we focused on the bond and cracking characteristics of polyvinyl alcohol (PVA)-FRCC reinforced with braided AFRP bars (AFRP/PVA-FRCC). Pullout tests on specimens with varying bond lengths were conducted. Beam specimens were also subjected to four-point bending tests. In the pullout tests, experimental parameters included the cross-sectional dimensions and the fiber volume fractions of PVA-FRCC. A trilinear model for the bond constitutive law (bond stress–loaded-end slip relationship) was proposed. In the pullout bond test with specimens of long bond length, bond strength was found to increase with increases in both the fiber volume fraction and the cross-sectional dimension of the specimens. Bond behavior in specimens of long bond length was analyzed numerically using the proposed bond constitutive law. The calculated average bond stress–loaded-end slip relationships favorably fitted the test results. In bending tests with AFRP/PVA-FRCC beam specimens, high ductility was indicated by the bridging effect of fibers. The number of cracks increased with increases in the fiber volume fraction of PVA-FRCC. In specimens with a fiber volume fraction of 2%, the load reached its maximum value due to compression fracture of the FRCC. The crack width in PVA-FRCC calculated by the predicted formula, considering the bond constitutive law and the fiber bridging law, showed good agreement with the reinforcement strain–crack width relationship obtained from the tests. Full article