Fibers, Volume 7, Issue 4 (April 2019) – 10 articles

The behaviors of the fresh and mechanical properties of self-compacting concrete (SCC) are different from those of normal concrete mix. Previous research has investigated the benefits of this concrete mix by incorporating different constituent materials. The current research aims to develop a steel fiber reinforcement (SFR)‒SCC mixture and to study the effectiveness of different cement replacement materials (CRMs) on the fresh and mechanical properties of the SFR‒SCC mixtures. CRMs have been used to replace cement content, and the use of different water/cement ratios may lower the cost of CRMs, which include microwave-incinerated rice husk ash, silica fume, and fly ash. Fresh behavior, such as flow and filling ability and capacity segregation, was examined by a special test in SCC on the basis of their specifications. Moreover, compressive and splitting tensile strength tests were determined to simulate the hardened behavior for the concrete specimens. Experimental findings showed that, the V-funnel and L-box were within the accepted range for SCC. Tensile and flexural strength increases upon the use of 10% silica fume were found when compared with other groups; the ideal percentage of steel fiber that should be combined in this hybrid was 2% of the total weight of the binder. Overall, steel fibers generated a heightened compressive and splitting tensile strength in the self-compacting concrete mixes. Full article

Melt spinning is an efficient platform to continuously produce fiber materials with multifunctional and novel properties at a large scale. This paper briefly reviews research works that reveal the morphology development of immiscible polymer blend fibers during melt spinning. The better understanding of the formation and development of morphology of polymer blend fibers during melt spinning could help us to generate desired morphologies and precisely control the final properties of fiber materials via the melt spinning process. Full article

We have investigated, in a numerical and experimental way, a refractive index (RI) sensor based on surface plasmon resonance (SPR) in a silver-coated light-diffusing fiber (LDF). The experimental tests were conducted using water-glycerine mixtures with refractive indices ranging from 1.332 to 1.388. In the considered refractive index range, the experimental results show a sensitivity of the SPR wavelength to the outer medium’s RI ranging from ~2600 to ~4700 nm/RIU, which is larger than the sensitivity recently reported for a gold-coated LDF sensor (~1200 to ~4000 nm/RIU). The silver-coated sensor is also shown to ensure a higher signal-to-noise ratio (SNR) compared to the gold-coated sensor. Full article

The desire to create sustainable development through research birthed this study. Over time, several authors have focused on the utilization of various chemical particulates as reinforcement constituents for metallic matric composites (MMCs) and aluminum metal matrix composites (AMMCs), which has thus far yielded positive outcomes for achieving the chemical, mechanical, microstructural, thermal, corrosion, and wear property improvement of various reinforced composites. However, this study focused on the search for the residing potentials in alternative materials that can be used as reinforcement particulates in place of the commonly used graphite, silicon nitride, titanium nitride, zirconium, and the likes. This study literarily revealed, via several reviews of literature, that the search for less expensive and easily procured materials with a silicon oxide and magnesium oxide chemical content instigated the utilization of materials from agricultural waste (agro-waste). According to the reviewed literature, some of the waste materials from agriculture that have been found to be useful for the particulate reinforcement of composites are groundnut shell, coconut shell, rice husk, breadfruit seed hull ash, aloe vera, bean pod ash, cow horn, and so on. It was discovered that processed agro-wastes in the form of powdery particulates have demonstrated great reinforcing abilities, as recorded in literature. In addition, they enhanced the mechanical properties of the various composites developed in comparison to the as-cast materials. Full article

Due to the negative environmental impacts of synthetic plastics, the development of biodegradable plastics for both industrial and commercial applications is essential today. Researchers have developed various starch-based composites for different applications. The present work investigates the corn and rice starch-based bioplastics for packaging applications. Various samples of bioplastics are produced, with different compositions of corn and rice starch, glycerol, citric acid, and gelatin. The tensile properties were improved after adding rice starch. However, water absorption and water solubility were reduced. On the basis of these results, the best sample was analyzed for thickness testing, biodegradability properties, SEM, hydrophilicity, thermogravimetric analysis, and sealing properties of bioplastic. The results show the suitability of rice and corn-based thermoplastic starch for packaging applications. Full article

The Mg-rich marbles of Precambrian rocks of Namibia are widely exploited and marketed abroad for ornamental purposes. Karibib marbles, named after the locality where the most important quarries are located, are commercially known as “White Rhino Marble”. They formed under greenschist facies metamorphic conditions and may be characterized by the presence of veins of tremolite. Although the quarries, whose exploited marbles contain tremolite, do not seem to be abundant, we decided to carry out a detailed mineralogical and petrographic study on Karibib marbles in order to point out the occurrence of tremolite, whose shape may vary from prismatic to acicular, even sometimes resembling the asbestiform habitus and its geometry within the rock. With this aim, we carried out optical microscopy, X-ray diffractometry, X-ray scanning electron microscopy, and micro-Raman investigations, and also imaged the 3D fabric with micro computed X-ray tomography. The study of white marbles from Namibia and their mineral phases has an important impact, since tremolite might split into thin fibers and, therefore, being potentially harmful, the presence of tremolite requires an analysis of the risks of exposure to asbestos. Full article

The increasing attention toward environmental aspects has led, also in the sector of construction materials, to the need for developing more eco-friendly solutions. Among several options, the employment of low energy raw materials appears as an efficient solution intended to enhance the sustainability of building structures. One of the applications moving in this direction is the use of plant fibers as a reinforcement in cement-based composites, hence named as natural textile reinforced mortar (NTRM) composites. Although representing a promising technique, there are still several open issues concerning the variability of plant fibers properties, the durability, and the mechanical compatibility with the mortar. This study aims at investigating the influence of an impregnation process on the thread’s morphology and on the mechanical response. Therefore, the geometry of dry and impregnated flax threads is identified by using scanning electron microscope (SEM) images analysis, and their mechanical response in tension is assessed. In addition, the fibers-to-mortar bond behavior is investigated by means of pull-out tests. The proposed results show that the impregnation procedure employed, although not improving the fibers-to matrix bond, leads to a standardisation of the threads morphology and reduces the thread’s deformability in tension, and paves the way for further investigations on a larger scale. Full article

In this study, ballistic experiments were performed to determine the critical velocity of a Twaron^® 2040 high-performance yarn transversely impacted by round projectiles. Four different round projectiles possessing a radius of curvature of 2 µm, 20 µm, 200 µm and 2 mm were used in this study. Load cells were mounted to the grips to measure the load history of the yarn upon impact. A high-speed camera was incorporated into the ballistic experimental setup to capture the failure process of the yarn upon impact. A scanning electron microscope was utilized to perform post-mortem failure analysis on the recovered specimens. The results showed that as the radius of curvature of the projectile increased, the critical velocity also increased. The critical velocities for all cases were bounded between those predicted from the Euler–Bernoulli beam and Smith models. Upon impact above the upper limit of the critical velocity, the axial loads revealed a demonstrative reduction. The failure surfaces changed from shear to fibrillation as the radius of curvature increased. For those specimens that failed in shear, Hertzian contact model was used to predict the critical velocity. Full article

Cyclohexanone is an important industrial intermediate in the synthesis of materials such as nylons, but preparing it efficiently through one-step hydrogenation of phenol is hindered by over-reduction to cyclohexanol. Using an efficient catalyst can enhance the selectivity of cyclohexanone at high phenol conversion. In this study, catalysts comprised of palladium nanoparticles supported on electrospun PVDF-HFP (polyvinylidene fluoride-co-hexafluoropropylene) nanofibers were prepared using the electrospinning technique. The catalysts were characterized using thermogravimetric analyzer (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM), and drop shape analyzer (DSA). The prepared catalysts were used to hydrogenate phenol into cyclohexanone in a batch reactor. The Pd/PVDF-HFP catalyst showed a very high product selectivity and high phenol conversion. The conversion of phenol achieved was 98% with 97% cyclohexanone selectivity in 7 h using 15 wt% of palladium (0.0021 moles) relative to phenol (0.0159 moles). The turnover number (TON) and turnover frequency (TOF) values calculated were 7.38 and 1.05 h⁻¹, respectively. This paper presents original research in heterogeneous catalysis using novel electrospun nanofibers. Multiphase hydrogenation of phenol to cyclohexanone over electrospun Pd/PVDF-HFP catalyst has not been reported by any researcher in the literature. This work will also provide a research window for the application of electrospun polymeric nanofibers in multiphase reactions. Full article

The tensile strength of single water-sized E-glass fibres that were thermally conditioned, either in air or under vacuum, was investigated. The vacuum removed water from the conditioning atmosphere, as well as the fibre surfaces, at room temperature but retained tensile strength of fibres treated in the absence of water were not significantly different from those thermally conditioned in a standard air furnace. The results suggest that water, either in the treatment atmosphere or on the surface of the fibres, is not a significant factor in fundamental glass fibre strength loss at an elevated temperature. It may, therefore, be necessary to consider alternative theories to explain this strength loss. Full article