Numerical and experimental investigation of laser-assisted fused filament fabrication of carbon fibre reinforced polyether-ether-ketone composites: Temperature field evolution and crystallisation behaviours

This study presents a parameterised finite element modelling approach to predict the temperature field evolution and crystallisation behaviour of short carbon fibre reinforced polyether-ether-ketone (SCF/PEEK) during laser-assisted fused filament fabrication (LAFFF). The model innovatively integrates dynamic laser-nozzle heat sources with the melting-crystallisation kinetics of materials, which effectively addresses the longstanding issues of thermal imbalance and non-uniform crystal distribution in composites additive manufacturing. Validated through thermocouple measurements, infrared monitoring, and differential scanning calorimetry, the framework achieves predictive accuracy within ± 5 % for average relative crystallinity and ± 20 % for crystal variance. This research uncovers the crucial role of laser induced through-thickness heat transfer, a characteristic that has not been previously evident in conventional FFF. The results show that optimised auxiliary heating parameters, with ambient temperatures ranging from 75–110 °C and laser power between 2–3 W, create a process window that balances crystallinity enhancement with defect mitigation. Laser preheating generates transient temperature cycles, prolonging the exposure of the material near the crystallisation peak temperature of 235 °C. Meanwhile, elevated ambient temperatures decrease thermal gradients, together expanding the crystallisation window. This synergistic effect boosts the average relative crystallinity by 60 %–82 % compared to conventional rapid - cooling FFF, reaching values similar to those of industrial - grade 3D printing systems. These insights pave the way for the optimisation of thermal conditions in LAFFF, reducing dependence on high-temperature equipment and expanding the applicability of SCF/PEEK 3D printing technology.