Studies of polymer/carbon nanotube (CNT) fibers typically focus on optimizing the overall properties, and the effects of structural variation on these properties are ignored. Thus, we investigated the longitudinal variation in the properties of CNT/polyvinylidene fluoride (CNT/PVDF) fibers prepared by wet spinning a solution of multi-walled nanotubes, PVDF, and dimethylacetamide. To this end, materials for the CNT/PVDF fiber were selected, and a dope solution was prepared using MWNT, PVDF, and dimethylacetamide (DMAc). To consider the process parameters that would affect the performance of the CNT/PVDF fiber during the wet-spinning process using the dope solution, the initial conditions for wet spinning were selected, including bath concentration, bath temperature, drying temperature, and elongation, and the CNT/PVDF fiber was spun under the corresponding conditions. Additionally, three performance stabilization processes were proposed to improve the initial conditions for wet spinning and manufacturing the fiber. Lastly, to confirm the reliability of the CNT/PVDF fiber in all sections, tensile strength, electrical conductivity, and cross-sectional images were analyzed for the 30 m, 60 m, and 90 m sections of the fiber, and the reliability of the wet-spinning process was verified.

This research was focused on identifying the effect of substructures on the ultimate loads of an offshore wind turbine. The ultimate loads of a National Renewable Energy Laboratory (NREL) 5-MW generic model were assessed for two kinds of substructures: the jacket and mono-pile. First, the NREL 5-MW generic model was implemented in the software GH-Bladed^TM by using data from the published NREL report. The specifications of the mono-pile and jacket structures came from the published NREL and UPWIND reports, respectively. Based on the design load cases and conditions taken from the International Electrotechnical Commission 61400-3 and the published UPWIND project report, we analyzed the ultimate loads of offshore wind turbines to determine the effect of the substructure type. Based on these results, the ultimate loads of mono-pile-type and jacket-type models were compared. As a result, we confirmed the deviation in M_x of the blade, all sections of the tower, F_x of a the hub, and F_x and F_y of the yaw-bearing sections, respectively. Copyright © 2015 John Wiley & Sons, Ltd.