Papers by Keyword: Hygrothermal Ageing

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Authors: Moyeen Ahmad Sawpan
Abstract: Durability of glass fibre reinforced polymer (GFRP) composite is an important research topic because the changes occur in GFRP composite with ageing can affect its properties and lifetime. For long term use, GFRP composites should be examined in real time and with reasonable in-service environments. However, this is not practical because the time involved would significantly delay product development and therefore, accelerated ageing technique is required. Conditioning in wet and elevated temperatures known as hygrothermal ageing is a very useful technique to evaluate the durability of GFRP composites in a reasonable timeframe. In this work, pultruded GFRP composites were aged in sea water and in dry conditions at 23, 55 and 75°C for 0, 8 and 20 months to assess the changes in shear properties (e.g. short beam shear strength, SBSS and transverse shear strength, TSS) and in glass transition temperature, Tg. After ageing in sea water for 20 months, SBSS was found to retain by about 101, 102 and 95% at 23, 55 and 75°C, respectively. On the other hand, SBSS was retained by around 106% after ageing in dry condition for 20 months at 55 and 75°C. TSS was found to retain by approximately 99, 95 and 91% after ageing in sea water for 20 months at 23, 55 and 75°C, respectively, whereas TSS of dry conditioned samples was retained by about 105 and 107% at 55 and 75°C, respectively. Tg, measured by dynamic mechanical thermal analyser, showed little change both in wet and dry conditions at different temperatures and time.
Authors: Khedoudja Laoubi, Nabila Belloul, Ali Ahmed Benyahia, Aîcha Sérier, Nourdine Ouali
Abstract: The aim of this work is the study of the long term behaviour of a laminated composite made in glass/polyester and aged in seawater at various temperatures. The results obtained show that the immersion in seawater causes ageing of the composite material. This was reflected first by a change in color of the material depending on the temperature of the immersion and the gel-coat loses its brightness. The infrared spectroscopy has confirmed activation of chemical degradation (hydrolysis of the resin and of the fibre/matrix interface, fibre degradation). This chemical degradation could be the cause of decrease in strength and ductility detected by analysing the behaviour of immersed testing specimens. It could also be the cause of the increase of absorption rate recorded for immersions exceeding 22 days.
Authors: Bhatti Imran Shaban, Yan Zhao
Abstract: Moisture severely affects aerospace structures and offshore platforms during their service life span. It deteriorates the mechanical performance of polymeric composites through long term and cyclic hygrothermal ageing. This reduction in mechanical performance must be considered during product design to ensure long-term structure endurance. In order to decide the long-term moisture effects on composite components, they are exposed to a rapid moisture conditioning. Presently the available qualified methodologies allowing only simple geometry and an assumption that diffusivity rates are independent of the flow path or direction. Therefore a more advanced finite element method is required. In this research work the finite-element analysis was performed to study the moisture diffusion in unidirectional composites. The final goal for this study was to determine the exposure time for rapid moisture conditioning that produces the most accurate moisture distribution in composite laminates.
Authors: A. Naceri
Abstract: This paper considers the analysis of the mechanical behaviour of a laminate constituted of 12 layers of glass fiber fabric/epoxy resin conditioned at different relative humidities of 0, 60 and 96% at 60 °C. The analysing of the experimental results obtained of hygrothermal ageing on the mechanical response has permited to show that the influence of the moisture concentration on the ultimate mechanical properties becomes significant and important for the composite conditioned at relative humidity of 96% to the periods I and II (state of saturation and ageing).
Authors: Imran Shaban Bhatti, Zhao Yan
Abstract: In this article moisture diffusion characterization of carbon fiber based polymeric composites (5428/CCF300 and 5405/CCF300) under recurrent hygrothermal ageingis investigated experimentally and numerically. Diffusion kinetics is studied by using Fickian and Langmuir diffusion models. Composite interface surfaces were closely studied by electron microscopy during the absorption/ desorption process, which revealed that micro-crack near weak interface provide passages for water diffuse.To simulate harsh service environment, understudied specimens were go through high humidity and high temperature (85°C and 120°C) conditions and then interlaminar shear strength (ILSS) properties of composites were determined. This study found that the interface property has effect on absorption/ desorption behaviour as well on ILSS. Validation of experimental results is carried out by using finite element analysis. In sum, this research attempts to analyze the behavior of carbon fiber composites underre current hygrothermal environment for the purposes oflong-term service prediction.
Authors: Zhen Lin, Li Fen Cao, Miao Miao Liu, Jun Xie, Dao Yan Feng, Zhi Qin Peng, Zhi Wen Hu
Abstract: The exposure of wool fabrics to light, humidity and heat are inevitable, which will accelerate their ageing, as time goes on. The exact influences of these factors were not being parallel compared and studied previously, but are very important for preparing suitable storage or display environment for wool fabrics, especially for those excavated old wools in history. Hereby, wool fabrics were treated by heat ageing, hydrothermal ageing, UV ageing and UV & ozone ageing to figure out the effects of light, humidity and heat on their physical and chemical changes resulted in the degradation of wool. The performances of the wool fabrics with different treatments were investigated by thermogravimetric analysis (TGA), angle contact test, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD), etc. It has been found that thermal ageing resulted in the maximum yellowness of the wool fabrics. Hydrothermal ageing was most functional in decreasing the breaking strength and crystallinity of the wool fabrics. UV lighting induced significant hydrophilicity increase on the surfaces of the wools. The addition of ozone on UV lighting did not facilitate the further ageing of wool fabrics much.
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