Anisotropic fluid diffusion in carbon fiber reinforced composite rods: Experimental, analytical and numerical study

Carbon fiber composite plastic (CFRP) rods immersed in water present a pronounced anisotropic diffusion behavior. Understanding and predicting this behavior is important as the mechanical properties of the material are influenced by the moisture content. A simple experimental procedure allowing identification of both radial and axial diffusivity is presented. The diffusivities are calculated based on a new anisotropic analytical or numerical analysis. The diffusivity in the axial direction was found to be 14.3 times the diffusivity in radial direction. The analytical and numerical approaches show a good agreement. A practical engineering case study is also presented: the moisture content profile of a carbon fiber rod inside a cylindrical metal end fitting for long exposure times (5, 10, 25 and 50 years).