Effect of fibre length and suspension concentration on alignment quality of discontinuous recycled carbon fibre

Recycling has been widely considered to be one of the crucial requirements for the continuous use and growth in composite material. In this paper, a hydrodynamic alignment process is devised for converting discontinuous random recycled carbon fibre into mats with a highly aligned orientation distribution. The process involves preparation of a fibre suspension stock, fibre alignment via a nozzle, filtration and aligned mat treatment. The aligned mat allows composites with higher volume content to be manufactured at lower moulding pressure thus keeping degradation of fibre length to a minimum. In the past, alignment processes have been focused on fibres shorter than 5mm as they provide good dispersion quality. In the existing work, an attempt was made to use longer fibres in the alignment process as route to potential enhancement of composite performance. In addition, fibre concentration in the suspension was increased in order to increase the process yield rate. The effect of using longer fibre lengths and more concentrated suspension on alignment quality is reported in this paper. Furthermore, the relationship between nozzle geometry and alignment quality is also investigated. Finally the mechanical properties of a composite laminate made from 3mm recycled fibre are explored.