Characterisation of recycled carbon fibre: Mechanical properties and surface chemistry

High strength carbon fibres were recycled from epoxy composite scrap using a fluidised bed process. The potential for reusing the fibre was investigated by assessing its quality in terms of mechanical properties and surface chemistry. Single fibre tensile tests, scanning electron microscopy for surface visualisation, X-ray photoelectron spectroscopy for characterisation of the surface chemistry and interfacial shear stress measurements were performed. The two types of recycled fibre considered showed a reduction in tensile strength 35% and 51% but no degradation in stiffness was found. The presence of hydroxyl, carboxyl and carbonyl functional groups was found on the surface of the recycled fibre and although a lower O/C ratio was lower, the surface chemistry was not unlike that of virgin fibre. Prepreg scrap was also heat-treated at the same temperature as the fluidised bed process in an ashing furnace to study the reduction in tensile properties.