In the present investigation, we successfully fabricate a hybrid polymer nanocomposite containing epoxy/polyester blend resin and graphene nanoplatelets (GNPs) by a novel technique. A high intensity ultrasonicator is used to obtain a homogeneous mixture of epoxy/polyester resin and graphene nanoplatelets. This mixture is then mixed with a hardener using a high-speed mechanical stirrer. The trapped air and reaction volatiles are removed from the mixture using high vacuum. The hot press casting method is used to make the nanocomposite specimens. Tensile tests, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) are performed on neat, 0.2 wt %, 0.5 wt %, 1 wt %, 1.5 wt % and 2 wt % GNP-reinforced epoxy/polyester blend resin to investigate the reinforcement effect on the thermal and mechanical properties of the nanocomposites. The results of this research indicate that the tensile strength of the novel nanocomposite material increases to 86.8% with the addition of a ratio of graphene nanoplatelets as low as 0.2 wt %. DMA results indicate that the 1 wt % GNP-reinforced epoxy/polyester nanocomposite possesses the highest storage modulus and glass transition temperature (Tg), as compared to neat epoxy/polyester or the other nanocomposite specimens. In addition, TGA results verify thethermal stability of the experimental specimens, regardless of the weight percentage of GNPs.

This study surveys the influences of travel speed, voltage, and intensity on the characteristics of low-carbon steel samples generated by the Wire Arc Additive Manufacturing (WAAM) technique. The results indicated that the WAAM samples have isotropy grain shape, with grain size number values varying from about 8 to 12. Interestingly, the WAAM sample achieves better mechanical properties with a higher ultimate tensile strength (UTS) value and higher elongation at break value than the original wire. The UTS value of the WAAM sample is 21–40% higher than the original steel wire. The WAAM sample with a travel rate of 350 mm·min⁻¹, a voltage of 24 V, and an electrical intensity of 120 A reaches the highest UTS value of 694 MPa. The WAAM sample with a travel rate of 400 mm·min⁻¹, a voltage of 22 V, and an electrical intensity of 170 A gains the lowest UTS value of 599 MPa. Moreover, the elongation values oscillate around 41–57%, two or three times higher than the original steel wire. SEM microstructure reveals a ductile fracture surface with dimples of the samples after the tensile test, indicating the toughness of the samples. The fracture surface also shows the equiaxial shape and grain size of the WAAM samples. According to Taguchi analyses, the travel rate factor greatly impacts grain size. The voltage factor has the highest effect on the UTS value. The intensity factor has the most significant impact on the elongation value.

Despite the high capital requirements, offshore wind and wave energy integrated stations (WWS) are an emerging and potential solution to optimize efficiency in renewable energy development. Decisions about installation location significantly influence their efficiency. This study examines and determines highly efficient and sustainable locations based on quantitative indicators and qualitative criteria. For this purpose, a novel dual-side behavioral spherical fuzzy multi-criteria decision-making (MCDM) approach was developed and applied for the case study of Vietnam. In the first stage, the behavioral Data Envelopment Analysis (B-DEA) model, constructed based on prospect theory, is applied to analyze locations according to quantitative indicators under decision makers’ psychological behavior consideration. In the second stage, a spherical fuzzy extension of the integration composed of the DEMATEL (decision-making trial and evaluation laboratory) and the EDAS (evaluation based on distance from average solution) methods helped to evaluate the locations. Based on the convergence in qualitative and quantitative analysis results, efficiency–sustainability positioning maps are established. The research provides recommendations for appropriate WWS locations from that visualization. The research compared findings with current development projects, plans, and policies in Vietnam for validation.

The global manufacturing supply chain has been disrupted by the negative impacts of the pandemic. In Southeast Asia, Vietnam’s manufacturing industry is one of the most strongly integrated with global and regional supply chains. The production strategies in the “new normal” are the key solution to the survival and sustainable development of manufacturers. This study aims to develop a two-stage framework to investigate the impacts of COVID-19 and the post-COVID-19 production strategies for Vietnam’s manufacturing industry. As a theoretical contribution, this study proposes a novel and robust integration approach, which combines the Ordinal Priority Approach (OPA) and Fuzzy Evaluation Based on Distance from Average Solution (Fuzzy EDAS), for the first time. The negative impacts of the pandemic were identified and weighted by the OPA method. Then, production strategies were comprehensively evaluated using the Fuzzy EDAS method. Findings indicate that digitization and on-site renewable energy are the most essential recovery strategies for manufacturing in Vietnam. These findings are validated by comparisons with the results of recent multiple criteria decision-making (MCDM) methods. Furthermore, weight sensitivity analysis reveals different suitability of strategies for short-term and long-term negative impacts. As a managerial implication, the multi-scenario ranking results help managers to make resource-allocation decisions for the implementation of post-COVID-19 production strategies.

The wire Arc Additive Manufacturing (WAAM) technique has evolved into a cutting-edge 3D printing technique. This study surveys the influences of trajectory on the characteristics of low-carbon steel samples generated by the WAAM technique. The results show that the grains in the WAAM samples are isotropic, with grain size numbers ranging from 7 to 12. Strategy 3, with a spiral trajectory, has the smallest grain size, while strategy 2, with a lean zigzag trajectory, has the largest. The variations in grain size are caused by differences in heat input and output during the printing process. The WAAM samples achieve a significantly higher UTS value than the original wire, demonstrating the WAAM technique’s benefit. Strategy 3, with a spiral trajectory, achieves the highest UTS value, 616.5 MPa, 24% higher than the original wire. The UTS values of strategy 1 (horizontal zigzag trajectory) and strategy 4 (curve zigzag trajectory) are comparable. WAAM samples have significantly higher elongation values than the original wire, with only 22% elongation. The sample with the highest elongation value, 47.2%, was produced by strategy 3. Strategy 2 has an elongation value of 37.9%. The value of elongation is proportional to the value of UTS. WAAM samples have average elastic modulus values of 95.8 GPa, 173.3 GPa, 92.2 GPa, and 83.9 GPa, corresponding to strategies 1, 2, 3, and 4. Only a strategy 2 sample has a similar elastic modulus value to the original wire. All samples have dimples on the fracture surface, indicating that the WAAM samples are ductile. These fracture surfaces’ equiaxial shape corresponds to the original microstructure’s equiaxial shape. The results provide the optimal trajectory for the WAAM products is the spiral trajectory, while the lean zigzag trajectory gains only modest characteristics.

The aim of this article is to investigate the effect of the ratio of fillers, such as multiwalled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs), as well as different matrix stiffnesses, on the tensile strength of epoxy/polyester material. These fillers are added to epoxy/polyester solutions in various ratios and mixed well before molding. Experimental specimens are then made by means of the hot press process and utilizing the same curing and postcuring conditions. To investigate the effect of the matrix stiffness on the mechanical property reinforcement role of MWCNTs and GNPs in the resulting nanocomposites, the variations in the mixture ratios of the epoxy/polyester blend and hardener are considered. The results show that the tensile strength of epoxy/polyester material increases its maximum value by approximately 86.3% with the addition of MWCNTs at a ratio of 1% and increases to 86.8% with the addition of a mere 0.2% ratio of GNPs. The morphologies of the fractured surfaces of the resulting nanocomposites are observed by a scanning electron microscope (SEM). It is expected that the experimental results will lead to the offering of low-cost, high-strength materials for applications in the automobile industry and the manufacturing of household products.