“…37,63 Moreover, the increase in plasticization at high temperature compared to room temperature, further deterioration of the fiber-matrix interface, causing the formation of more micro-voids in the composite structure, also causes more water absorption. 37,38 Figure 7.Maximum mass change ratio of all composite groups.…”
Section: Resultsmentioning
confidence: 99%
“…37,63 Moreover, the increase in plasticization at high temperature compared to room temperature, further deterioration of the fiber-matrix interface, causing the formation of more micro-voids in the composite structure, also causes more water absorption. 37,38 The maximum water intake rate for different composite groups showed the addition of glass fabric to hybrid composites restricted to water ingress. Hybrid AGA composites absorbed more water than hybrid GAG composites for both water type and temperatures.…”
This paper evaluated the effect of water adsorption on the tensile characteristics of hybrid aramid/glass/epoxy composites. The composite samples ([G6]S, [A6]S, [G3A3]S, [A3G3]S immersed in hydrothermal aging conditions (distilled water at 25°C, distilled water at 70°C, seawater at 25°C, seawater at 70°C) for 1000 h. The kinetic diffusion parameters of hybrid and plain specimens were evaluated experimentally and theoretically. Further, the effects of the stacking sequence of fabrics, seawater/distilled water aging, and temperature on the tensile behavior of dry, wet, and re-dried specimens were systematically discussed. At the end of the test, SEM images were obtained from the surfaces of the broken samples. Water gain plots for various conditions displayed that the samples absorbed more water when the aramid fabrics were on the outer surface of the hybrid composites. The hydrothermal aging significantly decreased the tensile strength of hybrid aramid/glass/epoxy and plain glass/epoxy composites. The tensile strength decrease rate of samples immersed in distilled water was higher than in seawater. Besides, the re-drying process induced more tensile strength degradation for both water types. SEM results showed that delaminations increased with aging and increasing temperature.
“…37,63 Moreover, the increase in plasticization at high temperature compared to room temperature, further deterioration of the fiber-matrix interface, causing the formation of more micro-voids in the composite structure, also causes more water absorption. 37,38 Figure 7.Maximum mass change ratio of all composite groups.…”
Section: Resultsmentioning
confidence: 99%
“…37,63 Moreover, the increase in plasticization at high temperature compared to room temperature, further deterioration of the fiber-matrix interface, causing the formation of more micro-voids in the composite structure, also causes more water absorption. 37,38 The maximum water intake rate for different composite groups showed the addition of glass fabric to hybrid composites restricted to water ingress. Hybrid AGA composites absorbed more water than hybrid GAG composites for both water type and temperatures.…”
This paper evaluated the effect of water adsorption on the tensile characteristics of hybrid aramid/glass/epoxy composites. The composite samples ([G6]S, [A6]S, [G3A3]S, [A3G3]S immersed in hydrothermal aging conditions (distilled water at 25°C, distilled water at 70°C, seawater at 25°C, seawater at 70°C) for 1000 h. The kinetic diffusion parameters of hybrid and plain specimens were evaluated experimentally and theoretically. Further, the effects of the stacking sequence of fabrics, seawater/distilled water aging, and temperature on the tensile behavior of dry, wet, and re-dried specimens were systematically discussed. At the end of the test, SEM images were obtained from the surfaces of the broken samples. Water gain plots for various conditions displayed that the samples absorbed more water when the aramid fabrics were on the outer surface of the hybrid composites. The hydrothermal aging significantly decreased the tensile strength of hybrid aramid/glass/epoxy and plain glass/epoxy composites. The tensile strength decrease rate of samples immersed in distilled water was higher than in seawater. Besides, the re-drying process induced more tensile strength degradation for both water types. SEM results showed that delaminations increased with aging and increasing temperature.
“…Changes in functional groups of the neat EP and HNT/EP nanocomposites were analyzed by specific wavenumbers. According to the previous studies, some peaks were applied to detect the chemical 10 Journal of Nanomaterials structure change of the EP (and its nanocomposites) or the EP suffered by aging conditions [36][37][38][39][40]. The peaks of all aged and nonaged samples at 3400 cm -1 belong to -OH groups.…”
Section: Flexural Properties Under Composite Aging Conditionsmentioning
The effects of aging conditions on the mechanical properties of epoxy resin (EP) with halloysite nanotube (HNT) were studied. The aging conditions include soaking in water at various temperatures, soaking in acid solution, soaking in alkali solution, thermal shock cycling (TSC), and soaking coupled with subsequent thermal shock cycling (i.e., composite aging conditions). Under aging conditions, the EP is degraded, plasticized, and swelled, resulting in different degrees of cracks and pores in EP. The tensile and bending properties of EP and HNT/EP nanocomposites decreased after aging, indicating that the durability of the EP decreased under aging conditions. The addition of HNT could improve the immersion aging resistance and delay the immersion aging behavior of EP. Under TSC conditions, the reduction in mechanical properties of HNT/EP nanocomposites with HNT is slightly more than that of the neat EP due to different thermal expansion coefficients between HNT and EP. The fracture morphology and chemical change were studied to reveal the aging degradation mechanisms in the presence of HNT addition.
“…It is widely used in electrical equipment as a packaging and pouring material. Existing studies have shown that moisture will accelerate the aging of epoxy resin material for power equipment and reduce its insulation performance [ 8 , 9 ]. After the intrusion of water molecules, physical and chemical changes such as plasticization and hydrolysis will occur in epoxy resin, resulting in irreversible crack, structural damage, and performance degradation of epoxy resin [ 10 , 11 , 12 ].…”
Moisture is detrimental to the performance of epoxy resin material for electrical equipment in long-term operation and insulation. Therefore, moisture absorption is one of the critical indicators for insulation of the material. However, some relevant test methods, e.g., the direct weighing method, are time-consuming, and it usually takes months to complete a test. For this, it is necessary to have some modification to save the test time. Firstly, the study analyzes the present prediction method (according to ISO 62:2008). Under the same accuracy, the time required is reduced from 104 days to 71 days. Subsequently, the Langmuir curve-fitting method for water absorption of epoxy resin is analyzed, and the initial values of diffusion coefficient, bonding coefficient, and de-bonding coefficient are determined based on the results of molecular simulation, relevant experiment, and literature review. With the optimized prediction model, it takes only 1.5 days (reduced by 98% as compared with the standard prediction method) to determine the moisture absorbability. Then, the factors influencing the prediction accuracy are discussed. The results have shown that the fluctuation of balance at the initial stage will affect the test precision significantly. Accordingly, this study proposes a quantitative characterization method for initial trace moisture based on the terahertz method, by which the trace moisture in epoxy resin is represented precisely through the established terahertz time-domain spectroscopy system. When this method is used to predict the moisture absorbability, the experimental time may be further shortened by 33% to 1 day. For the whole water absorption cycle curve, the error is less than 5%.
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