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Land shortage in metropolitan vicinities entails subsurface implementation of power transmission lines (PTLs) which demand structural flexibility, as well as substantial load bearing capability. Thus, development of a flexible gas insulated transmission line (FGIL) necessitates its strength degradation analysis, regarding the synergistic effect of aging and mechanical loadings. Moreover, correlation of conductor and enclosure dimensions of FGIL apropos field distribution, requires careful consideration regarding their dimensional specifications. In this research, a comprehensive electro-mechanical design is performed for the proposed flexible-thermoplastic-enclosure of a 132 kV FGIL by considering the synergistic impact of time and temperature-based aging, along with the effect of external and internal loadings, such as dead load, live load and internal gas pressure. Additionally, a recursive design algorithm for the proposed scheme regarding electro-mechanical aspects, along with aging perspectives is developed. Comparative analysis of proposed and conventional schemes regarding electro-mechanical and aging aspects revealed that the proposed enclosure exhibits the required structural strength, as well as flexibility for trenchless subsurface application of FGILs in metropolitan areas.

Short fiber–reinforced hybrid polymer (SFRHP) composites were prepared using short glass fibers (SGFs) and short carbon fibers (SCFs) as the reinforcements and vinyl ester resin as the matrix. The flexural properties of all-SGF, all-SCF, and SGF-SCF hybrid composites with controlled fiber orientation were found out experimentally and also predicted using rule of hybrid mixtures. Hand layup technique was used for the preparation of the composites. Composites with different patterns of fiber alignment were prepared and their properties were compared with randomly oriented short fiber composites. The results showed that the flexural performance of samples with longitudinal orientation of the fibers was significantly better than randomly oriented samples for all composites. Synergistic effect of hybridization (positive hybridization) with respect to flexural properties of SFRHP composites was obtained by controlling the orientation of the fibers. It was shown that the hybridization of fibers in the short fiber composites can provide economic savings.

Gas insulated transmission lines (GILs) are being used in electrical systems regarding power transmission and substation interconnection. However, operational complexities of conventional schemes, such as structural rigidity, corrosion protection, gas leakage in case of seismic vibrations, larger bending radius and jointing complexities which restrain their application perspectives, could be curtailed by developing a flexible GIL. In this research paper, a new pliable scheme of gas insulated transmission line is proposed. Further, COMSOL Multiphysics® (version 5.1, COMSOL Inc., Stockholm, Sweden) based electrostatic assay and practically performed high voltage tests-based dielectric analysis is performed for the proposed scheme. Electrostatic appraisal is comprised of field utilization based electrostatic stress analysis. In addition, dimensional optimization of pliable GIL regarding enclosure and pitch sizes in relation to electrostatic stresses and field utilization is also performed. Regarding dielectric perusal, experimental setup has been developed for standard lightning impulse and disruptive discharge tests in order to investigate the synergistic dielectric characteristics of proposed flexible post insulators for pliable GIL. Experimental and simulation appraisal unveil that the proposed scheme exhibits almost analogous electrostatic and dielectric behavior in comparison to the conventional GIL scheme and could simplify the operational intricacies associated with conventional scheme. The proposed modifications could eliminate the requirement of trench development, corrosion protection and acceleration dampers, along with a significant reduction in required land area at bends, due to a smaller bending radius which will ultimately result in substantial cost reduction.

The implementation of stranded conductors in flexible gas-insulated transmission lines (FGILs) requires field intensity minimization as well as field irregularity suppression in order to avoid dielectric breakdown. Moreover, the interdependence of enclosure and conductor sizes of FGILs regarding electrostatic aspects necessitate critical consideration of their dimensional specifications. In this research, geometric and electrostatic field optimization for FGILs regarding stranded conductors is performed. In addition, the effect of conductor irregularity on field dispersion is analyzed, and a semiconducting film (SCF)-coated stranded conductor is proposed as a potential candidate for FGILs. Considering the performed optimized design, an 11 kV scaled-down model of a 132-kV FGIL was also fabricated in order to practically analyze its electrostatic and dielectric performances regarding simple and SCF-coated stranded conductors. Simulation and experimental investigations revealed that the SCF-coated stranded conductor significantly minimized the field irregularity of the FGIL along with improving in its dielectric breakdown characteristics.

In order to enhance salt rejection level and high pressure mechanical integrity, functionalized nanokaolin decorated multiwall carbon nanotubes (FNKM, 0–5 wt % loading) were incorporated into a cellulose acetate (CA) matrix using high temperature solution mixing methodology. Scanning electron microscopy (SEM), X-ray diffraction technique (XRD), thermo-gravimetric analyzer (TGA) and Fourier transform infrared spectrometer (FTIR) were used to characterize the prepared membranes. The obtained results revealed that with increasing FNKM concentration in the host polymeric matrix, composite membrane’s structural, functional, thermal, water permeation/flux and salt rejection characteristics were also modified accordingly. Percent enhancement in salt rejection was increased around threefold by adding 5 wt % FNKM in CA.

The primary aim of the research reported in this paper is to study the influence of the type of dopant, used in the synthesis of polyaniline, on the physico-mechanical and electrical properties of polyaniline filled composites. Polyaniline (PAni) doped with four different dopants was used as a filler in the interpenetrating polymer networks (IPNs) of polymethyl methacrylate (PMMA) and polyurethane (PU). The dopants used in the synthesis of PAni included inorganic dopants (hydrochloric acid (HCl), sulphuric acid (H2SO4)) and organic dopants (p-Toluenesulfonic acid (PTSA), camphor sulphonic acid (CSA)). Physico-mechanical properties of the filled-IPNs, tensile strength, hardness, elongation at break and Young's modulus were determined along with electrical conductivity. Chemical resistance of the IPNs against different acids and bases was also determined. It was observed that the properties of PAni filled PU/PMMA IPNs were a strong function of the type of dopant used in the synthesis of PAni.

Aramid fiber–reinforced polymer composite (AFRPC) is popular in aerospace and defense industries owing to its superior thermal and mechanical properties. However, its intricate hexagonal cellular structure and the material’s heterogeneous, soft, and brittle characteristics lead to significant surface defects, such as burr formation, wall tearing, roughness, dimensional inaccuracies, and uncut fibers during traditional machining. Such poor machining quality issues notably affect the operational lifespan and functional performance of its sandwich structural components. To address these issues, the rotary ultrasonic assisted machining (RUSAM) process has been introduced. To thoroughly investigate the RUSAM of AFRPC using various cutting tools, a 3D finite element model was developed and validated. This paper mainly investigates the effect of various machining parameters such as vibration amplitude (VA), cutting width (CW), feed rate (FR), and spindle speed (SS) on the cutting force, surface morphology, burr formation, and burr height during RUSAM of AFRPC structure by plane and toothed disc cutters. The burr height was found to decrease with the increase of spindle speed (60.82% and 71.00%) and vibration amplitude (78.15% and 82.32%), whereas increase with cutting width ( 149.81 % and 321.16%) and feed rate (156.53% and 314.83%) during RUSAM by plane and toothed disc cutters, respectively. The pattern of variation of burr height with machining parameters was found similar to that of the cutting force. Significance analysis based on 4 levels, 4 factors orthogonal L 16 ( 4 4 ) experiments revealed the cutting width to be the most influential parameter on the burr height and cutting force followed by the spindle speed, feed rate, and vibration amplitude during RUSAM of the AFRPC core by the disc cutters. Up to 62.54 % reduction in burr height was realized by rotary ultrasonic assisted machining compared to the conventional machining. Under specified operating conditions, the disc cutter generates a higher but less number of burr as compared to the toothed disc cutter without any tearing defects. 3–10% and 5–20% burrs were observed during rotary ultrasonic assisted machining compared to 20–50% and 40–70% burrs during conventional machining of AFRPC structure by plane and toothed disc cutters, respectively. This experimental research will be extremely useful to comprehend the burr formation mechanism and optimize the machining parameters for enhanced surface morphology of AFRPC structures.

The applications of Nomex honeycomb composite (NHC) structures in aerospace, automotive and defence sectors have been significantly increasing due to their high compressive strength, hexagonal thin-walled structure, ultra-light weight and excellent thermal resistance. Specific applications include composite sandwich structures in helicopter propellers, satellite cabins, aeroplane floors, engine cowls, wings and nacelles. Accuracy of the machined surface of NHC structures is required for adhesive bonding with face-sheets. Conventional machining processes generate machining defects in terms of tearing, damaged cell walls, burr formation, delamination and poor surface quality that result in reduction of strengths of the core structure and its bond with face sheet. Ultrasonic machining is a proven technique to overcome such machining defects and improve the surface quality of NHC structures. Novelty of this research includes the development of a three-dimensional (3D) finite element model to analyse cutting forces, chip formation and machining quality of NHC structures using disc cutter through both ultrasonic and conventional machining processes by providing feed to the workpiece instead of the cutting tool. The significant influence of machining parameters such as depth of cut, feed rate, ultrasonic amplitude and spindle speed on cutting forces was investigated numerically followed by experimental validation. Numerical model in support with experimental results show that cutting forces decrease by increasing ultrasonic amplitude and spindle speed (up to 54.74% and 62.71%, respectively), and increase with the increase of depth of cut and feed rate (up to 60% and 60.48%, respectively). It was also found that the ultrasonic machining reduces the magnitude of cutting forces as compared to conventional machining (up to 42.74%). Surface morphology analysis through scanning electron microscope also indicated improved machining quality achieved by ultrasonic machining at NHC structures’ hexagonal cells, triple points and walls. A burr formation of 5% was observed during ultrasonic machining of NHC structures for Fy≤3N, while it was found up to 10% if Fy>3N, compared to at least 30% burr during conventional machining. To sum up, the employed methodology can be effectively applied for determining the effect of various machining parameters on cutting forces as well as surface quality, chip formation, structural integrity and dimensional accuracy of machined NHC structures during ultrasonic machining process.

Elastomeric composites based on ethylene propylene diene monomer (EPDM) filled with polyaniline (PANI) doped with dodecylbenzene sulfonic acid were prepared by in situ polymerization. The thermal, mechanical, and electrical properties of the resulting blend have been investigated via different characterization techniques. The interaction between the blend components was investigated by Fourier transform infrared spectroscopy (FTIR). Electrochemical impedance spectroscopy (EIS) was used to carry out the charge conduction studies of EPDM-PANI blends. The blend was solution polymerized and the sample was obtained in the form of a sheet. Since polyaniline acts as a conducting polymer and its concentration influences the electrical as well as the mechanical properties of the final product.

Thermoplastic polyurethane/polyaniline-based stretchable strain sensors were prepared via in situ polymerization of aniline in the TPU solution in the form of thin films. The sensors where characterized for morphological and thermal properties, mechanical hysteresis and cyclic piezoelectric performance. Thermogravimetric analysis showed blends to be thermally stable up to 230 °C. Electrical conductivity increased up to 30 wt% of Ani.DBSA loading after which a decline was observed due to reduced conversion of aniline monomer to polyaniline. Piezo-resistive measurements also showed a decrease in electrical conductivity upon stretching due to disconnection mechanism between Ani.DBSA particles. The cyclic piezo-resistive properties were evaluated at a strain of 10%. The sensors showed a gauge factor of 2.59. The dispersion and distribution was uniform at all levels of Ani.DBSA loading as visualized by SEM analysis. Beside uniform dispersion, SEM analysis also revealed polyaniline chains connecting with the polyurethane matrix which increases its conductivity. Hence, the proposed sensors can be employed as flexible strain sensors.