Fibers

Shielding of instruments and humans from electromagnetic interference (EMI) has become increasingly important during the last decades due to more and more machines and devices radiating electromagnetic waves. While several applications can use rigid shields, more flexibility is enabled by developing bendable, drapable, ideally even stretchable EMI shielding. Textile fabrics can have these properties, combined with potentially good mechanical properties, depending on the textile structure and the chosen material. On the other hand, the necessary physical properties, especially conductivity and magnetic properties, cannot be taken for granted in normal textile fabrics. These properties have to be added by conductive yarn or layer coatings, integration of conductive or magnetic fibers, producing intrinsically conductive or magnetic fibers, etc. The article gives a critical comparison of the properties of materials typically used for this purpose, such as intrinsically conductive polymers, metal-coated fabrics and metal wires, MXene coatings, MXene fibers, carbon coatings, and fibers. The review concentrates on thematically suitable papers found in the Web of Science and Google Scholar from the last five years and shows that especially MXenes are highly investigated recently due to their high conductivity and EMI shielding effectiveness, while other conductive and magnetic coatings and fibers are nevertheless still interesting for the preparation of EMI shielding textile fabrics. Full article

This work presents a fabricated silica few-mode microstructured optical fiber (MOF) with a special six GeO₂-doped core geometry, an outer diameter of 125 µm (that corresponds to conventional commercially available telecommunication optical fibers), and improved induced twisting up to 500 revolutions per 1 m (under a rotation speed of 1000 revolutions per meter with a drawing speed of ~2 m per minute). The article discusses some technological aspects and issues of manufacturing the above-described twisted MOFs with complicated structures and geometry as GeO₂-doped silica supporting elements for them. We present results of some measurements performed for fabricated samples of chiral silica six-GeO₂-doped-core few-mode MOFs with various orders of twisting and both step and graded refractive indexes of “cores”. These tests contain research on MOF geometrical parameters, attenuation, and measurements of the far-field laser beam profile. Full article

Climate change, biomass utilization, and bioenergy recovery are among the biggest current global concerns. Wood is considered an environmentally benign material. Nevertheless, it must be processed for desired applications. Upon thermal treatment ranging from 180 °C to 280 °C, under low oxygen concentrations, wood becomes a material with improved dimensional stability, resistance to fungal attacks, grindability, hydrophobicity, and storage stability. Several strategies for wood treatment have been investigated over the course of the past decades, including the use of steam, nitrogen, smoke, vacuum, water, and hot oil. The goal of this work is to investigate the influence of pressure and atmosphere on the torrefaction of poplar. Through a systematic analysis of poplar wood samples treated under reduced pressures and different atmospheres, while keeping the same heating profile, it was possible to establish that changes observed for mass loss, color change, wood composition (via TGA/DTG analysis), functional groups (via FTIR), elemental analysis, and X-ray diffractograms relate directly to known reaction pathways occurring during torrefaction. Changes observed under reduced pressures have been associated with the relative concentration of oxygen in the reaction atmosphere and to the reduced diffusion times experienced by reactive by-products during the treatment. Conversely, extended diffusion times resulted in more significant changes for reactions carried out under N₂, water vapor, and air. Full article

Environmental sustainability and environmental protection are key to shaping the built environment. The use of environmentally sustainable materials in architecture is essential to transform urban centers into modern, sustainable cities, reducing the pollution of air and natural ecosystems, lowering gas emissions, and improving the energy efficiency of structures. In this study, corn processing waste was used as a reinforcing material to create a plaster matrix composite material for use as a sound absorption material. Specimens of two thicknesses were created, and the sound absorption coefficient (SAC) was measured by applying the normal incidence technique. Subsequently, a simulation model for predicting SAC using Artificial Neural Network (ANN) algorithms was utilized to compare the absorption performance of the specimens. The fibers extracted from the corn stem significantly improved the sound absorption performance of the gypsum matrix specimens. This is due to the increase in the porosity of the material caused by the adhesion between the fiber and the plaster which creates air pockets due to the roughness of the fiber. The simulation model appears to be effective in predicting the absorption properties of the material, as indicated by the results. Full article

This work addresses the feasibility of using waste badminton string fiber in cement and polymer matrices. A badminton racquet, once used, is torn and needs replacement with new strings. These torn strings, once cut from the badminton racquet system, become waste, and these fibers cannot be recycled and remain debris. Hence, this study examines the microstructural and mechanical properties of new fibers and old torn fibers comparatively. Scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy are used to study the microstructural properties of the fiber. Direct tensile stress is applied to new and old fibers in the universal testing machine varying by one, three, and five strands of the fibers and varying the gauge length to 60, 80, and 100 mm, and the respective energy absorption is calculated. From investigation with a varying number of strands, similar results were observed in both old and new fibers from energy absorption and residual force ratio. From investigation with varying gauge length, the tensile stress of new fibers varies between 648.53 and 749.03 MPa, and that of old fibers is 537.40–625.55 MPa. Young’s modulus for new and old fibers is 4870.00 and 4843.50 MPa, respectively. The Weibull statistical approach is used to test the variability of test results. The Weibull modulus varies between 5.27 and 9.17, which shows lower variability. Thus, the tensile stress results obtained for the discarded badminton fibers pave way for incorporating these fibers in cement and polymer matrices to improve the matrix properties. Full article

Due to the high cost of laboratory testing, many researchers are considering developing methods to predict the behavior of unreinforced and reinforced wood beams. This work aims to create either numerical or analytical models useful for extrapolating already conducted tests to other schemes/materials used as reinforcement. In the case of timber structures, due to the complexity of timber, this task is difficult. The first part of the article presents an analysis of the suitability of using a simplified mathematical model based on the equivalent cross-section method to describe the behavior of unreinforced and reinforced with carbon-fibre-reinforced polymer (CFRP) composite full-size laminated veneer lumber (LVL) beams. The theoretical results were compared with the results of conducted experimental tests. The scope of the analysis includes the estimation of modulus of rupture, bending stiffness, and determination of the neutral axis position. The equivalent cross-section method showed good agreement in determining the bending stiffness and neutral axis position of the strengthened sections. However, the suitability of using the equivalent cross-section method to estimate the load-carrying capacity of a cross-section reinforced with fiber composites still needs to be confirmed, which, according to the authors, is due to the differences between the assumed (linear) and actual (nonlinear) strain distribution in the compression zone. The second part uses the equivalent cross-section method to estimate the predicted bending stiffness of LVL beams strengthened with aramid-fibre-reinforced polymer (AFRP), glass-fibre-reinforced polymer (GFRP), and ultra-high modulus carbon-fibre-reinforced polymer (CFRP UHM) sheets. The proposed method can be used for preliminary evaluation of strengthening effectiveness of LVL beams. Full article

The poor flexural and damping properties of building materials damages concrete structures and affects their service life when concrete structures are subjected to dynamic loads. Three different dosages (i.e., 0%, 0.3%, and 0.6%) of organic phosphonates (HEDP.4Na) and different pouring methods (i.e., conventional pouring method, 90°-induced pouring method, and 150°-induced pouring method) were designed to improve the flexural and damping performance of fiber-reinforced alkali-activated slag composites (FR-AASC). The enhanced mechanism of HEDP.4Na was revealed by phase analysis (X-ray diffraction, XRD), pore structure analysis (Mercury Intrusion Porosimetry, MIP), the heat of hydration, and scanning electron microscopy (SEM) analysis. The results showed that 0.3% HEDP.4Na combined with the 150°-induced pouring angle can significantly improve the mechanical properties of the FR-AASC sample compared with the reference group. The sample with 0.3% HEDP.4Na cast by the 150°-induced pouring angle increased compressive and flexural strength, damping energy consumption and storage modulus by 20%, 60%, 78%, and 30%, respectively, compared with the reference sample cast by the conventional pouring methodology. HEDP.4Na reduced the early hydration heat and total porosity of the FR-AASC matrix, modified the fiber–matrix interface transition zone, and increased the frictional energy consumption of steel fibers. Overall, the synergistic effect of HEDP.4Na and the induced pouring methodology significantly improved the flexural and damping properties of FR-AASC. This study can provide a guidance for improving the flexural and damping capacity of FR-AASC and promote the application of FR-AASC in construction engineering. Full article

Gas-filled hollow-core fibers are a convenient tool for laser pulse compression down to a few-cycle duration. The development of compact, efficient and high quality compression schemes for laser pulses of relatively low μJ-level energies is of particular interest. In this work, temporal pulse compression based on nonlinear spectral broadening in a xenon-filled revolver fiber followed by a chirped mirror system is investigated. A 250 fs pulse at a central wavelength of 1.03 μm is compressed to 13.3 fs when the xenon pressure was tuned to provide zero group velocity dispersion near 1.03 μm. The energies of input and compressed pulses are 3.8 and 2.7 μJ, respectively. The compression quality factor of 1.8 is achieved. Full article

Over the years, scientists have been continually striving to develop innovative solutions to design and fabricate medicines with improved therapeutic potential. Conventional dosage forms, such as tablets, capsules, and injections, are limited when exploited for advanced therapeutics, such as drug targeting. To cater to these limitations, nanofibres have emerged as novel nanomaterials to provide enhanced bioavailability, targeted drug release, extended drug release profile, minimum toxicity, and reduced dosage frequency, which has indisputably improved patient adherence and compliance. This review will concern understanding the potential of drug-loaded nanofibres in drug delivery while comprehending a detailed description of their different production methods. The literature has been thoroughly reviewed to appreciate their potential in developing nanofibrous-based pharmaceutical formulations. Overall, this review has highlighted the importance, versatility, and adaptability of nanofibres in developing medicines with varied drug release kinetics. Several problems must be resolved for their full commercial realisation, such as the drug loading, the initial burst effect, the residual organic solvent, the stability of active agents, and the combined usage of new or existing biocompatible polymers. Full article

Fibre-reinforced shotcrete (sprayed concrete) is one of the major components in the support system for tunnels in hard rock. Several empirical design methodologies have been developed over the years due to the complexity and many uncertainties involved in rock support design. Therefore, this paper aims to highlight how the choice of design methodology and fibre type impacts the structural capacity of the lining and the emission of greenhouse gases (GHG). The paper starts with a review of different design methods. Then, an experimental campaign is presented in which the structural performance of shotcrete reinforced with various dosages of fibres made of steel, synthetic and basalt was compared. A case study is presented in which the permanent rock support is designed based on the presented design methods. Here, only the structural requirements were considered, and suitable dosages of fibres were selected based on the experimental results. The emission of GHG was calculated for all design options based on environmental product declarations for each fibre type. The result in this paper indicates that synthetic fibres have the greatest potential to lower the emissions of GHG in the design phase. Moreover, the choice of design method has a significant impact on the required dosage of fibres. Full article

In this study, structural thin-layer sandwich walls (SWs) made of steel-fibre-reinforced concrete (SFRC) without conventional reinforcements were investigated. Other researchers have shown that SWs with thin wythes can be used as load bearing structures in low-rise buildings, thereby reducing the amount of concrete by 2–5 times if compared to conventional reinforced-concrete SWs. In most studies, relatively warm climatic regions are the focus, and thin-layer SWs with shear connectors to obtain a certain level of composite action are investigated. In almost no studies has sound insulation been evaluated. In this study, a numerical investigation of structural, thermal and sound insulation performances was carried out. The load-bearing capacities of composite and non-composite SWs are compared. Regions with the lowest five-day mean air temperature of −20 ${}^{\circ }$C were considered. The characteristics of the SW are compared to the requirements given in relevant European and Latvian standards. The minimum thermal insulation for family houses varies from 120 mm to 200 mm, depending on the material. To ensure sufficient sound insulation, the average thickness of the concrete wythes should be around 60 mm, preferably with a 15 mm difference between them. Structural analysis of the proposed wall panel was performed using non-linear finite element analysis software ATENA Science. The obtained load-bearing capacity exceeded the design loads of a single-story family house by around 100 times, regardless of the degree of composite action. Full article

Environmental sustainability and environmental protection represent essential challenges for the well-being of the community. The use of eco-sustainable materials in architecture is necessary for the transformation of urban centers into modern sustainable cities, to reduce air pollution and protect natural ecosystems, decrease greenhouse gas emissions and improve the energy efficiency of buildings. In this study, sugar cane processing waste was used as an alternative and ecological acoustic material, combining it with natural binders used in construction, such as plaster and clay. To make the composite, the fibers were separated from the bark, then the fibers were assembled with the binder in the frames, and finally the frame with the composite was subjected to a drying process. Specimens of various thicknesses were prepared and the sound absorption coefficient (SAC) at normal incidence was calculated. Subsequently, to compare the acoustic performances of the samples, a simulation model for the prediction of the SAC based on the artificial neural network (ANN) was created. The results suggest the adoption of the simulation model to review the acoustic properties of the material. Full article

The article summarizes the state of the art in carbon-reinforced geopolymers. It takes into consideration various types of matrices and types of carbon fibers (CFs). The article shows the growing importance of this composite in the investigation conducted in recent years. Today, it is one of the most promising modern research areas, taking into account the decrease in the prices of CFs and their appearance on the market waste-based CFs, as well as research on new methods of producing CFs from sustainable precursors. The research methods applied in the article are critical analyses of the literature. The results of the literature analysis are discussed in a comparative context, including production methods and the influence of CFs on geopolymer properties. The potential applications for carbon fiber-reinforced geopolymer composites are shown. Additionally, the current research challenges for geopolymer composites reinforced by CFs are presented. Full article

This work reports the use of cross-linkers in bio-based blends from hydroxypropyl-modified lignin (TcC) and a bio-based polyamide (PA1010) for possible use as carbon fibre precursors, which, while minimising their effects on melt processing into filaments, assist in cross-linking components during the subsequent thermal stabilisation stage. Cross-linkers included a highly sterically hindered aliphatic hydrocarbon (Perkadox 30, PdX), a mono-functional organic peroxide (Triganox 311, TnX), and two different hydroxyalkylamides (Primid^® XL-552 (PmD 552) and Primid^® QM-1260 (PmD 1260)). The characterisation of melt-compounded samples of TcC/PA1010 containing PdX and TnX indicated considerable cross-linking via FTIR, DSC, DMA and rheology measurements. While both Primids showed some evidence of cross-linking, it was less than with PdX and TnX. This was corroborated via melt spinning of the melt-compounded chips or pellet-coated TcC/PA1010, each with cross-linker via a continuous, sub-pilot scale, melt-spinning process, where both Primids showed better processability. With the latter technique, while filaments could be produced, they were very brittle. To overcome this, melt-spun TcC/PA1010 filaments were immersed in aqueous solutions of PmD 552 and PmD 1260 at 80 °C. The resultant filaments could be easily thermally stabilised and showed evidence of cross-linking, producing higher char residues than the control filaments in the TGA experiments. Full article

Production and use of plastic products have drastically increased during the past decades and their environmental impacts are increasingly spotlighted. At the same time, coarse wool, a by-product of meat and dairy production, goes largely unexploited in the EU. This paper asks why more coarse wool is not used in consumer goods, such as acoustic and sound-absorbing products, garden products, and sanitary products. This is answered through a SWOT analysis of results from a desktop study and interviews with producers of these products made from wool, as well as policy documents relating to wool, waste, textiles, and plastic. Findings show that on a product level, the many inherent properties of wool create opportunities for product development and sustainability improvements and that using the coarser wool represents an opportunity for replacing plastics in many applications as well as for innovation. This is, however, dependent on local infrastructure and small-scale enterprises, but as such, it creates opportunities for local value chains, value creation, and safeguarding of local heritage. The shift to small-scale and local resource utilization requires systemic change on several levels: Here the findings show that policy can incentivize material usage transitions, but that these tools are little employed currently. Full article

For several decades, carbon fibers have been used for lightweight engineering in aircraft automotive and sports industries, mostly based on high-quality polyacrylonitrile (PAN). We investigated a novel PAN-based precursor fiber (PF) modified with a polycyclic aromatic hydrocarbon, namely hexabenzocoronene (HBC), which is expected to improve the thermal conversion process and to create a carbon fiber (CF) with enhanced mechanical properties. For this purpose, the novel PF and a spun-like homopolymeric PAN-based PF were thermally stabilized and carbonized in continuous lab-scale plants. The effect of the additive HBC on the conversion processes, fiber diameter and shape, density, and mechanical properties were investigated. The results showed that HBC seems to support stabilization reactions, and HBC/PAN-based PF show potentially higher stretchability of PF and stabilized fiber. The modified CF showed an improvement in Young’s modulus of about 25% at the same tensile strength compared to the unmodified PAN-based CF, resulting from enhanced crystalline orientation. The results showed a high potential of the HBC/PAN for energy-efficient production. In particular, the influence on tensile strength and modulus under optimized process conditions, as well as the possibility to use low quality PAN, need to be further investigated. Full article

The specific interest for the use of bark in materials, instead than for energy recovery, is owed to circular economy considerations, since bark fibers are normally byproducts or even waste from other sectors, and therefore their use would globally reduce the amount of refuse by replacing other materials in the production of composites. For the purpose of promoting their application in polymer composites, mainly under a geometry of short random fibers, bark fibers are extracted and treated, normally chemically by alkali. Following this, investigations are increasingly carried out on their chemical composition. More specifically, this includes measuring cellulose, hemicellulose, and lignin content and their modification with treatment on their thermal properties and degradation profile, and on the mechanical performance of the fibers and of the tentatively obtained composites. This work aims at reviewing the current state of studies, trying to elicit which bark fibers might be most promising among the potentially enormous number of these, clarifying which of these have received some attention in literature and trying to elicit the reason for this specific interest. These can be more thoroughly characterized for the purpose of further use, also in competition with other fibers not from bark, but from bast, leaves, etc., and pertaining to developed production systems (cotton, hemp, flax, jute, etc.). The latter are already widely employed in the production of composites, a possibility scantly explored so far for bark fibers. However, some initial works on bark fiber composites and both thermoplastic and thermosetting are indicated and the importance of some parameters (aspect ratio, chemical treatment) is discussed. Full article

Textile fibers have become a major issue in the debate on sustainable fashion and clothing consumption. While consumers are encouraged to choose more sustainable and circular textile materials, studies have indicated that a reduction in production and consumption has the greatest potential to reduce the total environmental impact. This can be considered an ecocentric perspective with a focus on degrowth as opposed to a technocentric view where new technologies are expected to solve environmental problems while economic growth continues. Based on a survey in Norway (N = 1284), we investigate how the techno- and ecocentric perspectives impact Norwegian consumers’ fiber preferences and perceptions and the corresponding effects on their clothing consumption. We found that the majority of consumers preferred natural fibers compared to synthetic materials. This contradicts current market practices and the recommendations by material sustainability comparison tools such as the Higg Material Sustainability Index (MSI), where many synthetics receive better ratings than natural fibers. We also found that perceptions of high sustainability regarding fibers were negatively correlated with reduced consumption. Our study suggests that a continued focus on material substitution and other technological measures for reducing climate change will impede the move toward sustainability in the textile sector. Full article