Water absorption in unsaturated polyester composites reinforced with caroa fiber fabrics: modeling and simulation

Studies on composites reinforced with natural fibers show that they are sensitive to influences from environmental agents such as water. The moisture causes degradation of the mechanical properties of natural fiber reinforced composites to a larger extent when compared to synthetic fiber reinforced composites. This is a consequence of the higher moisture absorption, and the organic nature of the natural fibers. In this sense, the purpose of this work was to study theoretically and experimentally water absorption in unsaturated polyester composites reinforced with caroa fiber at 25, 50 and 70 degrees C. The composites had a weight composition of 30% caroa and 70% unsaturated polyester with dimensions of 20 x 20 x 3 mm(3) and 20 x 20 x 6 mm(3). Water absorption tests were conducted by immersing samples in a distilled water bath and the water uptake was followed gravimetrically for different elapsed time. A three-dimensional mathematical model was developed to predict the mass transfer during the water absorption in parallelepiped solids. Results of water absorption kinetic and moisture content distribution inside these composites are shown and analyzed. The knowledge of this moisture distribution allows verifying more favorable areas which presents delamination problems due to the weakness of the fiber-matrix interface and consequently reduction in the mechanical properties. It was verified that moisture induced degradation of composite samples was significant at elevated temperature.