Moisture diffusion model of composites considering fiber/matrix inter phase

A three-phase moisture diffusion approach of composites was developed based upon the Halpin & Tsais model by analogizing the governing equations and boundary conditions of moisture diffusion and heat conduction. In this approach, the moisture diffusion effect of fiber/matrix inter-phase was taken into account. Three types of micro-scale FE models, i.e. hexagonally, randomly packed fibers and randomly distributed inter-phase damage, were built to valid the theoretical model. The predictions from theoretical approach and FE models are in good agreements under the conditions of various volume fractions, diffusivities of fiber and inter-phase as well as randomness of inter-phase damage. Critical inter-phase and fiber moisture diffusivities, independent on fiber volume fraction, are found in this study. When the inter-phase or fiber diffusivity is less than the critical value, the transverse effective moisture diffusivity of unidirectional composite(TEMDUC) will decrease with the increase of fiber volume fraction. On the contrary, the trend is opposite. Also, the fluctuation range of composites' effective moisture diffusivities is found narrow with the change of inter-phase damage distribution if the damage ratio has been given.