Process-dependent multiscale modeling for 3D printing of continuous fiber-reinforced composites

Three-dimensional (3D) printing has broad application prospects in the field of lightweight composite structures due to its superior manufacturing flexibility. However, current 3D-printed continuous fiber-reinforced thermoplastic (CFRTP) parts and components suffer from poor mechanical properties due to processing defects that arise from poor resin impregnation in fiber bundles. Impregnation only occurs when the resin is molten. Hence, the evolution of the thermal field in the local space being printed is critical to determine the degree of resin impregnation. In this paper, we presented a new method to regulate the transient 3D thermal field during printing via an external laser heat source, thus effectively improving the resin impregnation of 3D-printed CFRTPs. To reveal their quantitative relations, the 3D thermal field and consequent impregnation behavior of resin in fiber bundles were numerically modeled. Furthermore, a process-dependent multiscale mechanical model was developed to investigate the tensile strength of 3D-printed composites based on the impregnation analysis framework. The parameters in the proposed models were determined experimentally. The thermal model was demonstrated and validated experimentally through thermocouple measurements. The impregnation percentage and tensile strength of the printed samples were determined using microscopy and tensile testing, respectively. Simulation results agreed well with experimental data, indicating the good accuracy of the proposed modeling methods. The findings provide insights into the process-impregnation-property relationship in 3D printing of CFRTP structures. Based on these findings, an effective method has been proposed to reduce printing defects and improve manufacturing efficiency by improving the thermal field.