Moisture sorption and mechanical degradation of VARTMed three-dimensional braided carbon-epoxy composites

The vacuum assisted resin transfer moulding process was employed to prepare three-dimensional (3D) braided carbon fibre-epoxy composites in this study. The moisture absorption and desorption behaviours of the 3D composites and their mechanical degradation were studied. A comparison with unidirectional carbon fibre-epoxy composites was made to evaluate the influence of fibre architecture. Similar to the unidirectional counterparts, the 3D composites displayed a Fickian diffusion behaviour during absorption and desorption processes. However, the difference in diffusion rate was observed between the 3D and unidirectional composites during adsorption, the 3D fabric showing a higher hindrance effect on moisture diffusion. During desorption, fibre structure did not show obvious effect on the diffusion behaviour. Mechanical tests revealed that the 3D composites presented lower losses in mechanical properties suggesting the 3D composites possessed higher moisture resistance than the unidirectional ones.