Preparation of Highly Aligned Recycled Carbon Fiber Mats via a Nozzle Orientation Technique and Performance Study of Their Reinforced Epoxy Composites

The random distribution of recycled carbon fibers (rCF) in composites severely limits their performance. To address this, a nozzle orientation technique (NOT) is proposed, in which a carbon fiber suspension is passed through a converging nozzle to generate a directional shear flow field, enabling the numerically controlled fabrication of highly aligned recycled fiber mats. Using these ordered mats as reinforcement, epoxy composites with fiber mass fractions of 20–40 wt% were prepared by compression molding and systematically compared with continuous carbon fiber prepreg composites and non-oriented mat composites. The ordered fiber structure forms efficient pathways for heat conduction and load transfer. At 40 wt% fiber content, the aligned mat composite achieves an in-plane thermal conductivity of 4.09 W·m⁻¹·K⁻¹ (102.48% higher than the random system, 30.8% lower than the continuous system), a tensile strength of 224.06 MPa (70.39% improvement over the random system), and a flexural strength of 232.19 MPa (71.87% improvement). This work provides an effective technical route for the controllable alignment and high-value recycling of rCF.