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To study the effect of the finishing process on the mechanical properties of polybutylene terephthalate/polyethylene terephthalate (PBT/PET) bicomponent polyester fiber, PBT/PET yarns were subjected to heat-moisture and dry-heat treatment at different temperatures and times. The tensile properties, elastic recovery, stress relaxation, and creep properties of the yarn were tested. The crystalline structure of PBT/PET fiber before and after heat treatment was studied by X-ray diffraction (XRD) to explain the change in yarn mechanical properties. The mechanical model of PBT/PET yarn was established, and the change in mechanical properties was investigated theoretically. The results show that the strength of PBT/PET yarn decreases by 10.77%, and the elongation increase by 34.81% after dry-hear treatment at 160°C for 25 min. The mechanical properties of the yarn are affected by the temperature and time of heat treatment. XRD analysis shows that the crystallinity of PBT/PET yarn decreases with the increase of heat treatment temperature and time, which may be the reason for the change in mechanical properties of PBT/PET yarn. In addition, the established model can fairly well explain the viscoelasticity of PBT/PET yarn. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced polyetheretherketone polymer (CF/PEEK) thermoplastic composites have a marked plastic yield stage compared to thermoset composites with epoxy matrix. During the interference fit riveting process, extrusion between rivet and composites laminate creates plastic deformation on the hole wall, which will enhance the bearing capacity of composites hole. Therefore, it is expected that the interference fit will play a greater advantage in enhancing the bearing strength of CF/PEEK riveted joint. Numerical and experimental study are applied to investigate the effect of interference fit on bearing strength of CF/PEEK riveted joint. Results show that the plastic deformation of CF/PEEK composites hole wall is positively correlated with the bearing strength of CF/PEEK riveted joint. When the interference fit size exceeds 2.6%, the bearing capacity of CF/PEEK riveted joint reduces because of the increase of fiber damage. It is concluded that the plastic deformation of riveted hole wall can enhance the bearing capacity of CF/PEEK riveted joint, while fiber damage reduces the bearing capacity of CF/PEEK riveted joint. As the increase of interference‐fit size, bearing strength of CF/PEEK riveted joint raises first then decreases, the appropriate interference‐fit size is in the range of 2.0% ~ 2.6%, which is larger than that of thermoset composites. [ABSTRACT FROM AUTHOR]

Poor management of nitrogen (N) can lead to serious environmental problems, such as air and water pollution. The accurate identification of priority control areas and emission sources is critical for making effective decisions regarding sustainable N management. This study aimed to identify hotspots for N losses and quantitatively analyze the relative contributions of different emission sources in the Huang-Huai-Hai Basin at the county scale. Specifically, it focused on N losses from agricultural production (crop production, livestock production, and freshwater aquaculture) and residential sources (urban sewage and rural domestic wastewater). To achieve this, we developed the Model to assess Anthropogenic Nitrogen losses to the Environment, following the mass flow analysis approach. The total N losses from agricultural production and residential sources in the Huang-Huai-Hai Basin were approximately 6.4 Tg per year in 2017, with 56% emitted to water and 44% to the air. Crop production and livestock production accounted for 46% and 45% of the total N losses, respectively. The main pathways of N loss were NH 3 emissions to the air (41%) and direct nitrogen discharge to water (28%). Hotspots of total N losses were identified in 202 out of 910 counties, primarily located in the Henan and Hebei provinces. Although these hotspots cover less than 7% of the total basin area, they account for 51% of the total N losses. The main driving factors leading to these hotspots are the number of livestock, followed by the use of chemical N fertilizers and the extent of cultivated area. The findings of this study provide important insights for the targeted control of anthropogenic reactive N loss in the Huang-Huai-Hai Basin., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)