Fibers — Open Access Journal

In this paper, new mineralogical and petrographical data of asbestiform Magnesio-riebeckite from ophiolite cropping out in the Pollino Unesco Global Geopark (southern Italy) are presented. Magnesio-riebeckite schists with HP-LT index mineral assemblage recorded metamorphic events in blueschist facies in the Frido Unit. Previous toxicological studies showed that asbestiform Magnesio-riebeckite species exhibited high carcinogenicity in previous intraperitoneal injection experiments with rats. The results have been obtained using different analytical techniques such as X-ray fluorescence (XRF), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and electron probe micro analysis (EPMA). Results show that all the samples contain fibrous Magnesio-riebeckite and/or prismatic, acicular crystals in aggregates. The concentration of elements in Magnesio-riebeckite crystals is: Na₂O (4.12–6.26 wt%), MgO (8.22–10.87 wt%), FeO (19.07–23.81 wt%), SiO₂ (52.05–56.06 wt%), CaO (1.12–4.53 wt%), Al₂O₃ (1.34–1.93 wt%), and MnO (0.10–0.34 wt%). Magnesio-riebeckite crystals are documented in the Pollino Unesco Global Geopark for the first time. For this reason, the aim of this paper is the characterization of Magnesio-riebeckite to improve the knowledge of this mineral in the studied area, because the release of fibers into the environment is dangerous for human health. Full article

During cotton fibers development, important structural changes occur, which lead to cellulose deposition and organization in the secondary cell wall. Several studies have focused on the analysis of the cell wall extracts of cotton fibers to gain an understanding of the changes in carbohydrate profiles and to determine the changes in crystallinity, cellulosic and non-cellulosic compounds at various stages of the fiber cell wall development. In this research, thermogravimetric analysis (TGA) was used to study intact fibers harvested from two cotton genotypes. Cellulose macromolecules structural changes occurring during different developmental stages were studied. The results from TGA technique were in agreement with results from other analytical techniques, which indicates that TGA could be a great tool to investigate the onset of cellulose deposition and to evaluate the cell wall composition during fiber development. The results obtained in this study demonstrated that the initiation of the secondary cell wall is genotype-dependent. Full article

The popularity of jute-based bio and hybrid composites is mainly due to an increase in environmental concerns and pollution. Jute fibers have low cost, high abundance, and reasonable mechanical properties. Research in all-natural fibers and composites have increased exponentially due to the environment concerns of the hazards of synthetic fibers-based composites. Jute based bio and hybrid composites have been extensively used in number of applications. Hybrid jute-based composites have enhanced mechanical and physical properties, reasonably better than jute fiber composites. A detailed analysis of jute-based bio and hybrid composites was carried out in this review. The primary aim of this review paper is to provide a critical analysis and to discuss all recent developments in jute-based composites. The content covers different aspects of jute-based composites, including their mechanical and physical properties, structure, morphology, chemical composition, fiber modification techniques, surface treatments, jute based hybrid composites, limitations, and applications. Jute-based composites are currently being used in a vast number of applications such as in textiles, construction, cosmetics, medical, packaging, automobile, and furniture industries. Full article

Electrospun fiber can be used as a carrier for releasing active ingredients at the target site to achieve the effects of drug treatment. The objectives of this research work were to study suitable conditions for producing electrospun gelatin fiber loaded with crude Curcuma comosa Roxb. extract (CE) and to study antioxidant, anti-tyrosinase and anti-bacterial activities and its freeze–thaw stability as well. To achieve optimal conditions for producing electrospun gelatin fiber, the concentration of gelatin was adjusted to 30% w/v in a co-solvent system of acetic acid/water (9:1 v/v) with a feed rate of 3 mL/h and an applied voltage of 15 kV. The lowest percent loading of 5% (w/v) CE in gelatin nanofiber exhibited the highest DPPH radical scavenging activity of 94% and the highest inhibition of tyrosinase enzyme of 35%. Moreover, the inhibition zones for antibacterial activities against S. aureus and S. epidermidis were 7.77 ± 0.21 and 7.73 ± 0.12 mm, respectively. The freeze–thaw stability of CE in electrospun gelatin nanofiber was significantly different (p < 0.05) after the 4th cycle as compared to CE. Electrospun gelatin nanofiber containing CE also showed the capacity of the release of bioactive ingredients possessing anti-oxidant properties and, therefore, it could potentially be used for face masks. Full article

In the last years, natural fibers are increasingly investigated as an oil recovery system in order to overcome the oil spillage phenomena, thus preserving environment and aquatic life. In particular, lignocellulose-based fibers have recently been employed with promising results. In such a context, the aim of this paper is to assess the oil sorption capability of natural fibers extracted from the stem of the giant reed Arundo donax L., a perennial rhizomatous grass belonging to the Poaceae family that grows naturally all around the world thanks to its ability to tolerate different climatic conditions. Sorption tests in several pollutants and water as a reference were carried out. The fibers have absorption capacities that are about five to six times their weight. Depending on the high absorption kinetics, possible applicative interests can be identified. Eventually, depending on the fiber size, adsorption properties were related to the microstructure and morphology of Arundo donax fibers. Full article

Our current study deals with the dye adsorption and electrical property of a partially carbonized composite fiber containing transition metal oxides including, iron oxide, nickel oxide, and titanium oxide. The fiber was made by electrospinning, carbonization, and hydrothermal treatment. During the electrospinning, titanium oxide particles were dispersed in polyacrylonitrile (PAN) polymer-dimethylformamide (DMF) solution. Nickel chloride and iron nitrate were added into the solution to generate nickel oxide and iron oxide in the subsequent heat treatment processes. The polymer fiber was oxidized first at an elevated temperature of 250 °C to stabilize the structure of PAN. Then, we performed higher temperature heat treatment at 500 °C in a furnace with hydrogen gas protection to partially carbonize the polymer fiber. After that, the oxide-containing fiber was coated with activated carbon in a diluted sugar solution via hydrothermal carbonization at 200 °C for 8 h. The pressure reached 1.45 MPa in the reaction chamber. The obtained product was tested in view of the dye, Rhodamine B, adsorption using a Vis-UV spectrometer. Electrical property characterization was performed using an electrochemical work station. It was found that the hydrothermally treated oxide-containing fiber demonstrated obvious dye adsorption behavior. The visible light absorption intensity of the Rhodamine B dye decreased with the increase in the soaking time of the fiber in the dye solution. The impedance of the fiber was increased due to the hydrothermal carbonization treatment. We also found that charge build-up was faster at the surface of the specimen without the hydrothermally treated carbon layer. Electricity generation under visible light excitation is more intensive at the hydrothermally treated fiber than at the one without the hydrothermal treatment. This result is consistent with that obtained from the dye adsorption/decomposition test because the charge generation is more efficient at the surface of the hydrothermally treated fiber, which allows the dye to be decomposed faster by the treated fibers with activated carbon. Full article

We discuss the fabrication of hollow-core optical fibers made of borosilicate glass. We show that, despite the high attenuation of the glass relative to silica, the fiber optical losses can be of the same order of magnitude of those obtained by using ultrapure silica glass. Short lengths of the fabricated fibers, used in combination with incoherent optical sources, provide single-mode optical guidance in both near and mid-infrared spectral ranges without any additional optical components. Full article

The strengthening and rehabilitation of concrete members is an important issue which arises worldwide. Carbon, aramid and glass fiber reinforced polymer (FRP) composites are mainly used for strengthening and rehabilitation. However, its use is limited on a small scale because of its high price, lack of availability and environmental impacts. The solution of this issue gives rise to the use of locally available natural fibers and low-cost synthetic fibers. This paper presents the experimental and analytical results of circular and square concrete columns confined with jute–polyester hybrid FRP composites. The main objective of this study is to evaluate the viability and performance of concrete confined with the hybridization of jute and polyester (FRP) composite sheets to utilize its superior properties. A novel hybrid technique has been applied for the wrapping of fiber sheets. The fiber sheets were applied in such a way that a uniform bond between the inner and outer layer was achieved. A total of 32 plain, standard size circular and square concrete specimens, externally wrapped with a jute–polyester FRP (JPFRP) composite, were tested under monotonic axial compressive loads. The result shows that JPFRP confinement increased the strength, strain and ductility index ranged between 1.24 and 2.61, 1.38 and 8.97, and 4.94 and 26.5 times the un-jacketed specimen, respectively. Furthermore, the wrapping has a significant effect on the low-strength specimens, having a circular cross-section. For high strength specimens, the post-peak stress-strain behavior was dominated by the outer polyester jacket because of its large rupture strain. Additionally, the test results were used to evaluate the existing strength-strain models derived for conventional FRPs. The models predicted values either underestimating or overestimating the compressive strength and strain of JPFRP-confined specimens. However, the strength models performed better than the strain models. The JPFRP wrapping significantly enhanced the strength, fracture energy, ductility index, and post-peak response. Therefore, JPFRP confinement can be used for a small-scale application, where little strength and high ductility is demanded. Moreover, it can be used to prevent the peeling of the concrete cover and moisture penetration into the concrete. Full article

Two new types of oxide fibers, namely, those of single crystalline yttrium-aluminum perovskite YAlO₃ (YAP) and two-phase YAlO₃-Y₄Al₂O₉ (YAP-YAM), have been grown by the internal crystallization method. The fibers of the second type retain their strength at temperatures up to 1000 °C. Their effective strength in a molybdenum matrix reaches about 600 MPa at a temperature of 1400 °C. Full article

With huge varieties of fabrics, the first challenge for any performance evaluation is to categorize the vast types of the products into fewer, more homogeneous and akin groups. Classification or sorting is arguably the first step of any scientific investigation, and comparison of product quality is meaningful only when conducted within a group of comparable products. A new criterion termed fabric linear density λ is first proposed in this paper so that fabrics can in general be divided into four groups. The derivation and validation of this parameter are provided. The importance of fabric drape is almost self-evident, but there are still no effective ways to easily measure this fabric attribute. A few existing instruments, notably the Cusick Drapemeter, suffer from low repeatability and low sensitivity and are hence not widely or frequently used. It is demonstrated in this study that, by using the PhabrOmeter, along with the fabric linear density λ, a much more efficient alternative for fabric drape test can be achieved. By actually testing 40 various fabrics, the principle, procedure and results of this method is presented in this paper. Full article

Good dispersion and interfacial compatibility are the key issues to realize the full potential of the physical–mechanical properties of nanocarbon-materials reinforced composites. Styrene–maleic-anhydride-copolymer (SMA)-treated graphene oxide (GO), carboxylated multiwalled carbon nanotubes (MWNTs-COOH), and solid-state shear milling (S3M) were applied to further improve the physical–mechanical properties of the nanocomposite fibers. The results show that a mixture of GO/MWNTs-COOH exhibits good dispersion and interfacial compatibility in polyamide-66 (PA66) matrix. Consequently, the physical–mechanical properties of the fibers, which were spun from the nanocomposite of GO/MWNTs-COOH treated using SMA and S3M methods, show a significant enhancement compared to the untreated fibers as well as better crystallization and thermal properties. In particular, the tensile strength of the PA66/GO/MWNTs-COOH nanocomposite fibers with a loading of 0.3 wt % GO/MWNTs-COOH reaches a maximum (979 MPa), which is the highest among all of the reported literature values. Moreover, the fibers were fabricated by a facile process with efficiency, holding great potential for industrial applications. Full article

The present experimental work investigates the applicability and performance of a new strengthening method for concrete slabs, intended to increase their punching resistance using combination layers of steel wire mesh with epoxy attached to the concrete slabs’ tension face. Six simply supported square reinforced concrete slab specimens were tested up to failure under a central concentrated load. The main parameters in the study are the concrete compressive strength (30 MPa and 65 MPa) and the configuration of a bundle externally fixed to the tension side of the tested slabs. The experimental results appeared to greatly enhance the performance of the specimens, as they were externally strengthenined under this new method. When compared to the control slabs, the punching load and stiffness of the strengthened slabs increased up to 28% and 21%, respectively. Full article

This paper studied the influence of fiber volume fraction ( $V_f$ ), fiber orientation, and type of reinforcement bar (rebar) on the uniaxial tensile behavior of rebar-reinforced strain-hardening ultra-high performance concrete (UHPC). It was observed that the tensile strength increased with the increase in $V_f$ . When $V_f$ was kept constant at 1%, rebar-reinforced UHPC with fibers aligned with the load direction registered the highest strength and that with fibers oriented perpendicular to the load direction recorded the lowest strength. The strength of the composite with random fibers laid in between. Moreover, the strength, as well as the ductility, increased when the normal strength grade 60 rebars embedded in UHPC were replaced with high strength grade 100 rebars with all other conditions remaining unchanged. In addition, this paper discusses the potential of sudden failure of rebar-reinforced strain hardening UHPC and it is suggested that the composite attains a minimum strain of 1% at the peak stress to enable the members to have sufficient ductility. Full article

Electrospinning and polymer blending have been the focus of research and the industry for their versatility, scalability, and potential applications across many different fields. In tissue engineering, nanofiber scaffolds composed of natural fibers, synthetic fibers, or a mixture of both have been reported. This review reports recent advances in polymer blended scaffolds for tissue engineering and the fabrication of functional scaffolds by electrospinning. A brief theory of electrospinning and the general setup as well as modifications used are presented. Polymer blends, including blends with natural polymers, synthetic polymers, mixture of natural and synthetic polymers, and nanofiller systems, are discussed in detail and reviewed. Full article

The experimental data presented in this work show the effects of nozzle diameter, drawing speed, and formation temperature on the diameter and strength of basalt filaments and melt flow rate. Several series of basalt continuous fibers were obtained using a specially designed crucible of platinum–rhodium alloy with four nozzles of different diameters (1.5, 2.5, 3.5, and 4.5 mm). The conditions of the process varied in formation temperature (from 1370 to 1450 °C) and winding speed (from 300 to 1200 m/min). Melt flow rate was almost independent of the winding speed, indicating laminar flow of the melt through the nozzles and the Newtonian nature of the liquid. The results show strict correlations between fiber diameter, nozzle diameter, and winding speed. The diameter of the fibers had a significant effect on their strength. The tensile strength of the obtained basalt fibers varied from 550 to 3320 MPa depending on the formation conditions. The results of this work could be useful not only for scientists, but also for technologists seeking the optimal conditions for technological processes. Full article

The surface topography and nanomechanical attributes of two samples of cotton fibers, namely, A and B, were characterized with various operation modes of an Atomic Force Microscope (AFM). The surface topography and friction images of the fibers were obtained in contact mode. The nanomechanical properties images—i.e., adhesion and deformation—were obtained in force tapping mode. The results indicate that the surface nanomechanical and nanoscale frictional properties of the fibers vary significantly between two samples. The plots of friction versus normal force of the fibers’ surface from both samples are fitted to the equation of single-asperity, adhesion-controlled friction. Nevertheless, within the range of the applied normal force, the friction curves of sample A surfaces show a characteristic transition phase. That is, under low normal forces, the friction curves closely conform with the Hertzian component of friction; after the transition takes place at higher normal forces, the friction curves follow Amontons’ law of friction. We demonstrated that the transition phase corresponds to a state at which the cuticle layer molecules are displaced from the fibers’ surface. The average adhesion force of the samples is consistent with the average friction signal strength collected under low normal forces. Full article

Basalt fiber is a novel type of inorganic fiber which is produced from the extrusion of natural vocalnic basalt rocks through their melting process at high temperature. So the quality and strength characteristics of basalt fiber depend mainly on both the quality of raw material and manufacturing processing. Basalt fabric-reinforced cementitious composites (FRCM) are a novel composite and an extensive scientific investigation is still ongoing for geopolymer composite. Based on three types of basalt textile with respect to various net sizes, the aim of this paper is to evaluate the flexural performance of basalt textile-reinforced geopolymer composite through the four-point bending test. The specimens of rectangular form with the dimension of 400 × 100 × 15 mm³, reinforced with one to four layers of each type of basalt textile, were produced. They were then tested at the age of about 40 days after casting. On the other hand, the number of the specimens reinforced with four layers were considered to assess the mechanical strength of the specimens at longer periods of ageing time (60, 90, 150, 180 days). The experimental results showed that with the increasing number of reinforcing layers, the specimens significantly improved the mechanical strength, except for those reinforced with basalt textile of big net size. The specimens reinforced with basalt textile of big net size had no impact on post-crack mechanical strength, however, it helps to arrest the catastrophic brittle failure of the specimens; the failure of these specimens is due to localization of first crack. When the specimens were exposed to the further ageing times, the mechanical strength of the specimens were decreased over time. All the reinforced specimens have the same failure mode by flexural failure due to the rupture of fiber yarn in matrix, and no debonding of fiber yarn or a gradual peeling process of mortar matrix happened during testing. Full article

Natural fibers, such as bamboo, flax, hemp, and coir, are usually different in terms of microstructure and chemical composition. The mechanical properties of natural fibers strongly depend on the organization of cell walls and the cellulose micro-fibril angle in the dominant cell wall layers. Bamboo, flax, and hemp are known for high strength and stiffness, while coir has high elongation to failure. Based on the unique properties of the fibers, fiber hybridization is expected to combine the advantages of different natural fibers for composite applications. In this paper, a study on bamboo/coir fiber hybrid composites was carried out to investigate the hybrid effect of tough coir fibers and brittle bamboo fibers in the composites. The tensile behavior of unidirectional composites of bamboo fibers, coir fibers, and hybrid bamboo/coir fibers with a thermoplastic matrix was studied. The correlation between the tensile properties of the fibers and of the hybrid composites was analyzed to understand the hybrid effects. In addition, the failure mode and fracture morphology of the hybrid composites were examined. The results suggested that, with a low bamboo fiber fraction, a positive hybrid effect with an increase of composite strain to failure was obtained, which can be attributed to the high strain to failure of the coir fibers; the bamboo fibers provided high stiffness and strength to the composites. Full article

By the in-line nanostructuring of glass fibres (GF) during the glass fibre melt spinning process, the authors achieve an electro-mechanical-response-sensor. The glass fibre interphase was functionalized with different highly electrically conductive carbon allotropes such as carbon nanotubes, graphene nanoplatelets, or conductive carbon black. On-line structural health monitoring is demonstrated in continuous glass fibre-reinforced polypropylene composites during a static or dynamic three-point bending test. The different carbon fillers exhibit qualitative differences in their signal quality and sensitivity due to the differences in the aspect ratio of the nanoparticles, the film homogeneity, and the associated electrically conductive network density in the interphase. The occurrence of irreversible signal changes during dynamic loading may be attributed to filler reorientation processes caused by polymer creeping or to the destruction of the electrically conductive paths due to the presence of cracks in the glass fibre interphase. Further, the authors found that sensor embedding hardly influences the tensile properties of continuous GF reinforced polypropylene (PP) composite. Full article