Analysis of moisture diffusion induced stress in carbon/epoxy 3D textile composite materials with voids by μ-CT based Finite Element Models

The present paper focuses on the analysis of moisture diffusion, induced swelling and stress in carbon/epoxy 3D textile composite materials with voids using mu-Computed Tomography (mu-CT) image-based Finite Element (FE) Models. Based on real images of the material, the FE model includes all the details of the textile architecture, texture defects and voids. The moisture diffusion coefficient of the resin is identified from an optimization procedure which fits the results of the FE analysis to the experimental data from water absorption tests. The model is then used for diffusion simulation in a material without voids and for calculation of diffusion induced swelling and stress. The effective diffusion properties of the composite material are calculated using FE analysis with periodic boundary conditions (PBC) and used for analytical-based simulation of the diffusion behaviour. It is shown that the mu CT image-based model does not predict Fickian behaviour, due to a microstructural effect. The mu CT image-based model can be employed for the simulation of the moisture induced stress in the different phases of the composite material. The equivalent homogeneous model in which diffusion properties are smeared in an equivalent homogeneous orthotropic material cannot emphasize the distinct effect of the different phases.