This work investigates the humidity absorption process in the polyester/glass fiber composite materials containing fillers and low profile additives. These composite materials were exposed to both distilled and sea water at different temperatures. The moisture diffusivity and the moisture equilibrium reached by these composites were determined using the gravimetric test method and their humidity distribution profile across the thickness direction was characterized using the microtome technique. The obtained results indicate that the distilled water diffuses in all composites much more rapidly than the sea water, particularly at high immersion temperatures. However, the opposite is observed at low immersion temperature (5°C), since at this temperature the distilled water is almost in its icy state. For high immersion temperatures, a mass loss of the aged specimen in the sea water was observed 2 months after the first immersion. Such behavior was not observed during the immersion in the distilled water. Moreover, it is observed that the water absorption is higher in the composite materials containing low profile additives. This behavior is explained in terms of microvoids formation promoted by low profile additives. The microtome technique reveals clearly that the humidity profile across the thickness of the aged specimen follows a parabolic trend with a maximum at the outside surface of that specimen and a minimum at its center. These experimental results were found to confirm the theory. POLYM. COMPOS., 28: 355–364, 2007. © 2007 Society of Plastics Engineers

This article investigates the dissymmetrical water absorption process in E‐glass fiber reinforced polyester composites containing fillers and low profile additives. Two different cases of dissymmetrical exposures to water were considered. In the first case, only one side of the aged specimen was exposed to water at different temperatures, the other side was exposed to air. In the second case, both sides were exposed to water, but at different temperatures on each side. The moisture diffusivity and the maximum moisture content reached by the composites were determined using the gravimetric test method. In the first case of the dissymmetrical immersion, the temperature inside the aged specimen was found to be almost constant and the kinetic of the water diffusion was found to obey perfectly the one‐dimensional Fick's second law. In the second case, the specimen temperature varies from one side to the other, thus preventing the use of Fick's laws. Alternatively, the use of the finite element code ABAQUS provided an excellent agreement between the experimental and simulated results in both cases of dissymmetrical immersions, as well as in the case of symmetrical immersion where the two sides were exposed to the same environmental conditions. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers

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This article studies the hygrothermal behavior of E-glass fiber-reinforced polyester composites containing filler additives. Three different cases of a material exposed to water are investigated at two various temperatures: 45℃ and 65℃. First, both lateral sides are exposed to water at the same temperature (symmetric absorption). Second, one side is exposed to water at a certain temperature and the other side is exposed to ambient air (dissymmetric absorption I). Third, both lateral sides are exposed to water at varied temperatures (dissymmetric absorption II). The kinetics of water absorption follows the Fick’s second law. The water concentration is higher on the surface of the material and it decreases continuously toward the core of the model. The increase in the temperature and the higher level of additives raise the absorbed moisture and the diffusion coefficient. The software “Abaqus” is used to simulate the water diffusion through the material. The comparison between the experimental and numerical results shows that the model can predict the hygrothermal behavior of the polyester/glass fiber in symmetric and dissymmetric absorption.

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