Water uptake studies of composite materials reinforced with vegetable fibers shows that they are highly sensitive to environmental influences such as water and temperature. The presence of moisture leads to impregnation and imperfect interfacial fiber-matrix adhesion, which generate internal stresses porosity and premature system failure. Accordingly, the aim of this work is to study theoretically water absorption in unsaturated polyester composites reinforced with caroá fiber (Neoglaziovia Variegata) at 25, 50 and 70°C by using a transient 3D mathematical model via ANSYS CFX® Software. The samples has composition 30% caroá fiber/70% unsaturated polyester resin and dimensions 6 x 20 x 20 mm3. Results of the average moisture content and moisture content distribution during the water uptake are presented and analyzed. Comparison between numerical and experimental data of the average moisture content showed good agreement. It can be concluded that the water absorption rate is faster in the vertex region of the composites, and mainly at higher temperature.

This paper focuses some fundamental aspects of combined convective and microwave drying of prolate spheroidal solids. A transient mathematical modeling based on the diffusion theory (mass and heat balance equations) written in prolate spheroidal coordinates was derived and the importance of this procedure on the analysis of the drying process of wet porous solid, is also presented. Results pointed to the behavior of the moisture migration and heating of the solid with different aspect ratio. Solids with higher area/volume relationships dry and heat faster.