Moisture absorption and interfacial failure in aramid/epoxy composites

Raman spectroscopy has been used to determine the effect of moisture absorption upon the point-to-point distribution of fibre strain for single-fibre model composite specimens and for different fibre surface treatments. The measurements have been undertaken using a cold-cured epoxy resin matrix immersed for various periods of time in distilled water at room temperature. Moisture absorption by the epoxy resin led to significant matrix swelling and a build up of axial strain in the reinforcing fibres. It has been demonstrated that Raman spectroscopy is an excellent technique to measure axial fibre strains resulting from matrix swelling for aramid fibres. It is also shown that the technique allows the onset of interfacial failure to be monitored during moisture uptake.