A power system is frequently exposed to overloading. This may introduces a number of unavoidable consequences as voltage sag, voltage dip and or power instability. This article advises remedy for such problems in a power system which is loaded by heavy static and dynamic loading levels. A multi-pulse D-STATCOM is to be incorporated in the power system under concern. The STATCOM generally enjoys the merits of fast response and reduced volumetric dimension. Moreover, it was investigated for boosting power system stability under different disturbance scenarios. However, a less is reported regarding stability under heavy loading condition. This article investigates design and analysis of application of multi-pulse D-STATCOM for improving voltage sag and power system stability under different loading types/levels. A simple and robust controller is advised for fulfilling the operation requirements. PSCAD software is used as platform for investigating the dynamic behavior of the system under concern. Comprehensive analysis and results are provided to validate the applicability and functionality of the D-STATCOM . The simulation results prove the capability of the D-STATCOM in mitigating voltage sag and enhancing power system stability while improving power quality of the distribution system.

A power system is frequently exposed to overloading. This may introduces a number of unavoidable consequences as voltage sag, voltage dip and or power instability. This article advises remedy for such problems in a power system which is loaded by heavy static and dynamic loading levels. A multi-pulse D-STATCOM is to be incorporated in the power system under concern. The STATCOM generally enjoys the merits of fast response and reduced volumetric dimension. Moreover, it was investigated for boosting power system stability under different disturbance scenarios. However, a less is reported regarding stability under heavy loading condition. This article investigates design and analysis of application of multi-pulse D-STATCOM for improving voltage sag and power system stability under different loading types/levels. A simple and robust controller is advised for fulfilling the operation requirements. PSCAD software is used as platform for investigating the dynamic behavior of the system under concern. Comprehensive analysis and results are provided to validate the applicability and functionality of the D-STATCOM . The simulation results prove the capability of the D-STATCOM in mitigating voltage sag and enhancing power system stability while improving power quality of the distribution system.

Inlet port design has a great influence on swirl generation inside the engine cylinder. In this paper, two helical inlet ports having the same helix design were suggested. The first has an upper entrance and the second has a side entrance. With the two ports, shrouded inlet valves having different conditions of shroud and orientation angles were used. Four shroud angles were used; they are 90o, 120o, 150o, and 180o. Also, four orientation angles were used; they are 0o, 30o, 60o, and 90o. 3D simulation model using the sst k- ? model was used for predicting the air flow characteristics through the inlet port and the engine cylinder in both intake and compression strokes. The results showed that the side entrance port produces swirl ratio higher that of the upper entrance port by about 3.5% while the volumetric efficiency is approximately the same for both ports. For both the ports, increasing the valve shroud angle increases the swirl ratio and reduces the volumetric efficiency. The maximum increments of swirl ratio relative to the ordinary valve case occur at valve conditions of 30o-150o, 00-180o, and 30o-180o. At these valve conditions, the swirl ratio values are 6.38, 6.72, and 6.95 at IVC with percentage increments of 69.2%, 78.2%, and 84.4%, respectively. The corresponding values of the volumetric efficiency are 93.6, 92.5, and 91.2, respectively with percentage decrements of 2.84%, 4%, and 5.7%, respectively.

Inlet port design has a great influence on swirl generation inside the engine cylinder. In this paper, two helical inlet ports having the same helix design were suggested. The first has an upper entrance and the second has a side entrance. With the two ports, shrouded inlet valves having different conditions of shroud and orientation angles were used. Four shroud angles were used; they are 90o, 120o, 150o, and 180o. Also, four orientation angles were used; they are 0o, 30o, 60o, and 90o. 3D simulation model using the sst k- ? model was used for predicting the air flow characteristics through the inlet port and the engine cylinder in both intake and compression strokes. The results showed that the side entrance port produces swirl ratio higher that of the upper entrance port by about 3.5% while the volumetric efficiency is approximately the same for both ports. For both the ports, increasing the valve shroud angle increases the swirl ratio and reduces the volumetric efficiency. The maximum increments of swirl ratio relative to the ordinary valve case occur at valve conditions of 30o-150o, 00-180o, and 30o-180o. At these valve conditions, the swirl ratio values are 6.38, 6.72, and 6.95 at IVC with percentage increments of 69.2%, 78.2%, and 84.4%, respectively. The corresponding values of the volumetric efficiency are 93.6, 92.5, and 91.2, respectively with percentage decrements of 2.84%, 4%, and 5.7%, respectively.

Carbon fiber reinforced polymer (CFRP) laminates exhibit limited fracture toughness due to characteristic interlaminar fiber-matrix cracking and delamination. In this article, we demonstrate that the fracture toughness of CFRP laminates can be improved by the addition of multi-walled carbon nanotubes (MWCNTs). Experimental investigations and numerical modeling were performed to determine the effects of using MWCNTs in CFRP laminates. The CFRP specimens were produced using an epoxy nanocomposite matrix reinforced with carboxyl functionalized multi-walled carbon nanotubes (COOH–MWCNTs). Four MWCNTs contents of 0.0%, 0.5%, 1.0%, and 1.5% per weight of the epoxy resin/hardener mixture were examined. Double cantilever beam (DCB) tests were performed to determine the mode I interlaminar fracture toughness of the unidirectional CFRP composites. This composite material property was quantified using the critical energy release rate, GIC. The experimental results show a 25%, 20%, and 17% increase in the maximum interlaminar fracture toughness of the CFRP composites with the addition of 0.5, 1.0, and 1.5 wt% MWCNTs, respectively. Microstructural investigations using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) verify that chemical reactions took place between the COOH–MWCNTs and the epoxy resin, supporting the improvements experimentally observed in the interlaminar fracture toughness of the CFRP specimens containing MWCNTs. Finite element (FE) simulations show good agreement with the experimental results and confirm the significant effect of MWCNTs on the interlaminar fracture toughness of CFRP.

The ability to fold and deploy lightweight composites without damage makes them attractive for aerospace applications. However, one of the challenges faced with deployable composites is their high stiffness, which results in a relatively high deployment rate. It has been hypothesized that by exploiting the time-dependent viscoelastic response of composites, the deployment process could be controlled. To investigate this hypothesis, the effect of matrix viscoelasticity on energy dissipation of a three-layer carbon fiber–reinforced polymer (CFRP) composite laminate, known as a composite tape spring, was examined during the stowage state. A time-dependent implicit finite-element model was generated and implemented to simulate the viscoelastic behavior of the orthotropic laminated CFRP composite tape spring. The implemented material model was verified against data from the literature, validated experimentally, and then used to investigate the significance of matrix stress relaxation on energy dissipation of the three-layer CFRP composite tape spring used in aerospace applications.

The structural design of the bolted fiber reinforced polymer elements is typically governed by the capacity of the joint rather than the fiber reinforced polymer member, while the joint capacity is typically governed by the shear strength of the fiber reinforced polymer. Here, the possibility of improving the shear strength of bolted joints is investigated in the unidirectional glass fiber reinforced polymer plates by incorporating the multiwalled carbon nanotubes during glass fiber reinforced polymer fabrication. Glass fiber reinforced polymer double-shear bolted lap joints were fabricated using up to 1.0 wt% multiwalled carbon nanotubes–-epoxy nanocomposites. Finite element modeling using multicontinuum theory and element deletion techniques was performed to explain the joint behavior. The experimental investigations show that incorporating multiwalled carbon nanotubes improved the shear strength, ductility, and energy absorption significantly. Microstructural analysis proves that a chemical reaction between multiwalled carbon nanotubes and epoxy improves the shear strength of the matrix.

Polymer concrete (PC) has been favoured over Portland cement concrete when low permeability, high adhesion, and/or high durability against aggressive environments are required. In this research, a new class of PC incorporating Multi-Walled Carbon Nanotubes (MWCNTs) is introduced. Four PC mixes with different MWCNTs contents were examined. MWCNTs were carefully dispersed in epoxy resin and then mixed with the hardener and aggregate to produce PC. The impact strength of the new PC was investigated by performing low-velocity impact tests. Other mechanical properties of the new PC including compressive, flexural, and shear strengths were also characterized. Moreover, microstructural characterization using scanning electron microscope and Fourier transform infrared spectroscopy of PC incorporating MWCNTs was performed. Impact test results showed that energy absorption of PC with 1.0 wt% MWCNTs by weight of epoxy resin was significantly improved by 36 % compared with conventional PC. Microstructural analysis demonstrated evidence that MWCNTs significantly altered the chemical structure of epoxy matrix. The changes in the microstructure lead to improvements in the impact resistance of PC, which would benefit the design of various PC structural elements.

This research article investigated the notch sensitivity of two different glass fibre architectures, namely short and 2D plain-woven glass fibres reinforced with unsaturated polyester and epoxy matrix composites fabricated by the hand lay-up technique. This was carried out through open hole tension tests at different ratios of the specimen hole diameter to the specimen with three different values (0.1, 0.2, 0.5) compared to the unnotched specimen. The notch sensitivity of these composites was evaluated using the residual tensile strength by the application of Whitney–Nuismer Mathematical Model. The results showed that by using polyester matrix, the notch sensitivity of composites reinforced with plain-woven glass fibre is higher than that of short glass fibre at different D/W ratios. On the other hand, on testing epoxy matrixes, the notch sensitivity of composites reinforced with plain-woven glass fibre is lower than that of short glass fibre at different D/W ratios.

This research article investigated the notch sensitivity of two different glass fibre architectures, namely short and 2D plain-woven glass fibres reinforced with unsaturated polyester and epoxy matrix composites fabricated by the hand lay-up technique. This was carried out through open hole tension tests at different ratios of the specimen hole diameter to the specimen with three different values (0.1, 0.2, 0.5) compared to the unnotched specimen. The notch sensitivity of these composites was evaluated using the residual tensile strength by the application of Whitney–Nuismer Mathematical Model. The results showed that by using polyester matrix, the notch sensitivity of composites reinforced with plain-woven glass fibre is higher than that of short glass fibre at different D/W ratios. On the other hand, on testing epoxy matrixes, the notch sensitivity of composites reinforced with plain-woven glass fibre is lower than that of short glass fibre at different D/W ratios.