Fibers, Volume 7, Issue 8 (August 2019) – 7 articles

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