Fibers, Volume 8, Issue 4 (April 2020) – 6 articles

Openings in reinforced concrete (RC) slabs are not commonly prescribed in design codes. Even when they are, they raise concerns regards to the size of the openings and the location of the applied loads. Lack of sufficient information about the load-carrying capacity of the slabs with openings and performance is another concern. Hence, this research addresses the structural behavior of slabs with openings coated with Carbon Fiber Reinforced Polymer (CFRP) sheet. In the experimental part, ten slabs were cast with a dimension of 1000 mm × 530 mm × 25 mm, among which nine slabs had openings and one slab was without opening (control slab). The configuration of the CFRP sheet includes coating in the form of single, double, and triple layers. Experimental results show that the slab with a triple coating of the CFRP layer offers the maximum resistance towards the loading rate. Moreover, with the increase in CFRP layers, the value of deflection is minimized. Full article

Advanced functionalities textiles embedding electronic fibers, yarns and fabrics are a demand for innovative smart cloths. Conductive electrospun membranes and yarns based on polyaniline/polyvinylpyrrolidone (PANI/PVP) were investigated using the chemical modification of PANI instead of using conventional coating processes as in-situ polymerization. PANI was synthesized from the aniline monomer and the influence of the oxidant-to-monomer ratio on electrical conductivity was studied. The optimized conductivity of pellets made with pressed PANI powders was 21 S·cm⁻¹. Yarns were then prepared from the t-Boc-PANI/PVP electrospun membranes followed by PANI protonation to enhance their electrical properties. Using this methodology, electrospun membranes and yarns were produced with electrical conductivities of 1.7 × 10⁻² and 4.1 × 10⁻⁴ S·cm⁻¹. Full article

Geogrid is as one of the component materials classified under the geosynthetics used for soil stabilizing and reinforcement. Due to its higher strength-to-weight ratio, ease of handling, and comparatively low costs, geogrid has been gradually explored for possible use in concrete reinforcement. This research aims to assess the feasibility of using geogrids as a possible reinforcement for high-strength self-compacted concrete slabs to provide additional tensile strength and ductility. To enhance the bond between geogrid layers and the cement matrix, two types of geogrid surface modification methods are introduced. Gluing sand to the geogrid surface as a physical surface modification method and immersion in polycarboxylate as a chemical surface modification method are investigated. The effect of geogrid type (uniaxial, biaxial and triaxial) and the number of layers is also introduced. The test results show that the chemical treatment increased the ultimate flexural loading capacity of the tested slab by about 8.5% for one geogrid layer and 13% for two geogrid layers compared to untreated specimens. This work was extended to add two geogrid layers in addition to the slab’s steel reinforcement. The results show that adding geogrid decreased the ultimate flexural loading capacity but significantly increased the slab ductility. Full article

The stable propagation of orbital angular momentum and cylindrical vector beams in a newly designed annular core photonic crystal fiber (AC-PCF) tailored for the broadband single-radial order beam transmission (within the so-called “endlessly mono-radial” guiding regime) is demonstrated for the first time. It is shown that the vector-vortex beams can maintain high mode purities above 18 dB after propagation in the fiber under test over all of the wavelength range from 805 to 845 nm (over 17 THz bandwidth) investigated with the help of a tunable laser and an S-plate for the generation of singular beams in free space. Our results confirm that the AC-PCF is a promising design for the broadband transmission of vector-vortex beams that have potential applications in space-division multiplexing, quantum communications, optical sensing and trapping. Full article

Cellulose nanocrystals (CNC) exhibit remarkable properties such as being lightweight, renewability, nanoscale dimension, raw material availability, and a unique morphology. They have been widely used in film-forming composites, but the literature is scarce concerning bulky-composites (i.e., non-filmogenic). Microcrystalline cellulose (MCC) is widely available and has emerged as an important material for the reinforcement of composites. This investigation focuses on the preparation of non-filmogenic composites prepared from a polyurethane-type matrix, based on modified lignosulfonate and castor oil, reinforced with CNC or MCC, aiming to compare their reinforcing capacity. CNC was obtained through the acid hydrolysis of MCC. Sodium lignosulfonate was chemically modified using glutaraldehyde to increase its reactivity towards isocyanate groups in the synthesis of lignopolyurethane. The results show that adding CNC or MCC led to materials with improved impact strength, flexural properties, and storage modulus compared to pristine lignopolyurethane. With the exception of the flexural modulus, which was higher for the CNC-reinforced composite compared to the MCC-reinforced composite, all other properties were similar. The set of results indicates that CNC and MCC are promising for the reinforcement of polyurethane-type matrices. Bulky materials with good properties and prepared from high renewable raw material contents were obtained, meeting current expectations concerning sustainable development. Full article

The current study investigates the effects of Fiber Reinforce Polymer (FRP) additive on the performance of Stone Mastic Asphalt (SMA) mixtures with SBS and Viatop Premium additives. The asphalt mixture used in the current study included SBS (Styrene-Butadiene-Styrene) additive modified at the rate of 5% according to the necessary preliminary studies, and some SMA mixture modified by adding FRP (Fiber Reinforced Polymers) additive prepared in dimensions of 5 cm in different proportions (0.3%, 0.5%, 0.7% and 0.9%). The mechanical properties of the mixtures were investigated, and the findings revealed that the SMA mixture; prepared by adding FRP additive, SBS modified bitumen, and Viatop Premium additive; increased the rutting, aging resistance and elasticity of SMAs. Moreover, load spread ability and fatigue life revealed an increase, whereas high temperature sensitivity and tendency to crack at low temperatures decreased throughout the study. The FRP contribution rate that improves the performance characteristics of the SMA mixture to the highest level was found to be 0.7%. Full article