Hydrothermal ageing mechanisms of unidirectional flax fabric reinforced epoxy composites

Hydrothermal ageing of plant fiber reinforced composites could cause degradation of mechanical properties due to the synergic effect of moisture and temperature. This paper explored the degradation mechanisms of plant fiber reinforced composites in the hydrothermal environment. The ageing behaviors of each component, i.e. the fiber, matrix and interface were investigated. Water absorption, dimensional variation and mechanical properties of the materials were continuously measured and analyzed. Supplementary methods of Scanning Electronic Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) were also employed in this study. Results revealed that the deterioration of flax fibers is the crucial factor for the ageing of plant fiber reinforced composites which is very different with that of synthetic fiber reinforced composites, where resin was the dominate component. A recovery study on the mechanical properties showed consistent results with other experimental results and analysis. Additionally, a systematic hydrothermal ageing mechanism was proposed.