X-ray micro-computed tomography investigation of fibre length degradation during the processing steps of short-fibre composites

The mechanical properties of composites in the fibre direction are mainly attributed to the fibre slenderness, or aspect ratio. A trade-off between performance and processability is usually required, and dependent on the intended application. If the fibre length could be retained or not severely degraded during various processing steps towards the injection-moulded component, a stiffer and stronger composite product could be obtained. The processing steps for injection moulded wood-fibre composites here include: pulping, commingling, extrusion, pelletizing, and injection moulding. To tune the processing parameters systematically for retained fibre length, it would be useful to investigate the degradation of the original fibre length distribution throughout the processing chain. The fibre length degradation has been monitored by X-ray micro-computed tomography through the processing steps in wood pulp-fibre reinforced polylactide. A significant fibre-length degradation was found. In particular, the extrusion step was found to result in a drastic fibre length reduction.