Theoretical approach. Solid materials absorb moisture when they are
immersed in water or when they are placed in a humid atmosphere, until the
process reaches an equilibrium state. However, in some cases, the omnipresent
latent heat effects may complicate the determination of the diffusivity.
Nevertheless, over the range of temperature and moisture concentration that
prevails in typical applications of composites, the thermal diffusivity is about 106
times greater than the moisture diffusion coefficient. Thus, the thermal diffusion
takes place 106 times faster than the moisture diffusion. As a result, the
temperature will reach the equilibrium long before the moisture concentration