Investigating the Interface of Natural Fibre-Resin Composites
The performance of emerging natural fibre composite materials relies on fibre-resin systems that are optimized to enable effective transfer of stress. The interfacial region of thin cross-sections of composite samples fabricated with a flax fibre mat and a bio-based epoxy resin, and a flax fibre mat with a synthetic epoxy resin were examined by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopic mapping. Imaging studies demonstrated that when excited with 405 nm laser excitation, flax fibres autofluoresce in the 410-513 nm wavelength range while there was neglible fluorescence signal from the surrounding resin matrix. The images confirmed that with both resin systems, there was wet-out of the flax fibre mats by the resin. SEM imaging of the cross-sectioned samples revealed some detachment of the fibres from the surrounding medium, with the separation space being larger in the composite samples fabricated with the synthetic resin. FTIR spectroscopic chemical maps showed that the flax fibre regions were dominated by spectral signals that can be assigned to the molecular C-O-C and C-O-H cellulose moieties of natural fibres. The spectra of the surrounding resin had peaks characteristic of the C-C aromatic molecules of epoxy resin. Although the spectra from the interfacial region between resin and fibre indicated mixed features suggesting a transition layer, there was no clear indication of new/shifted spectral peaks to suggest an obvious chemical interaction between the fibre and resin. This observation leads to the speculation that for the resin-fibre composite systems investigated in these studies, micromechanical interactions are the dominant mechansims of interaction.
Author: Lin-P'ing Choo-Smith
Conference: SAMPE Seattle 2017