A novel overflow extrusion‐annealing process for preparing high performance recycled carbon fiber reinforced Nylon 6 composites

The recycled carbon fiber reinforced polymer (rCFRP) based on fused filament fabrication possesses many problems, such as high porosity and poor interlayer bonding. In view of this, an overflow extrusion‐annealing process is proposed in this paper, in which rCFRP is prepared by using the extrusion flow higher than the theoretical requirement, and then annealed. Experimental outcomes demonstrate that recycled carbon fiber reinforced Nylon 6 (rCF/PA6) composites with a carbon fiber content of 35.5 wt% were successfully prepared by a developed screw extrusion 3D printer. The pore size distribution and micromorphology of rCF/PA6 composites show that the process can eliminate the inter‐bead pores, reduce the total porosity, and effectively promotes the interline and interlayer bonding. Mechanical properties tests reveal that compared with pure PA6, the tensile strength of rCF/PA6 composites prepared by this process is increased by 87.4% (100.41 MPa), and the flexural strength is increased by 71% (150.5 MPa). Therefore, this process has great potential in the preparation of high‐performance rCFRP, and is expected to provide a new perspective for the industrial application of 3D printed rCFRP in the future. Highlights Utilize recycled carbon fiber (rCF) in screw extrusion 3D printing. Prepare rCF/PA6 composites with a high rCF content. Eliminate inter‐bead pores based on overflow extrusion. Enhance interline and interlayer bonding of composites based on annealing. A novel overflow extrusion‐annealing process.