Impact of mold temperature and fiber velocity on impregnation in carbon fiber polyamide 66 composites

Thermoplastic fiber-reinforced composites are increasingly used in industrial applications due to their exceptional mechanical properties, recyclability, and thermal stability. However, their manufacturing process poses significant challenges including high processing temperature and pressures required for resin impregnation, which can lead to void contents incomplete fiber wetting and potential thermal degradation. Existing models, such as Darcy law, inadequately describe the non-Newtonian behavior of thermoplastic melts including shear thinning and viscoelasticity limiting their ability to optimize impregnation processes. This study develops a comprehensive multi-physics model that integrates Darcy law with Carreau–Yasuda viscosity model to predict resin flow dynamics, pressure gradient, and impregnation efficiency. Polyamide 66 (PA66) reinforced with carbon fibers was used to validate the model experimentally under varying temperatures (320 and 330 °C) and fiber velocities (1.5 and 2 m/min). The results show that the optimal impregnation occurs at 330 °C and 1.5 m/min, where reduced viscosity enhances resin flow, minimizes voids contents, and improves carbon fiber-polyamide 66 (CFPA66) bonding. The experimental results validate the mathematical model predictions.