Impregnation process of large-tow carbon-fiber woven fabric/polyamide 6 composites using solvent method

Large-tow carbon fibers (CF) are suitable for low-cost industrial applications. However, it is challenging to impregnate large fiber bundles with thermoplastics owing to their high melt viscosity. In this study, polyamide 6 (PA 6) is dissolved in a mixture of calcium chloride and methanol to decrease its viscosity, and a large-tow CF fabric is immersed in the solution. Subsequently, the solvent is removed with water and the fabric is dried. Scanning electron microscopy observations indicate that many PA6 particles are present inside the fiber bundles owing to solution impregnation. Thereafter, compression molding is conducted using a stack of additional PA6 films. The fabricated composites exhibit much better impregnation quality than those fabricated without solution impregnation. The quality of impregnation is also impacted by the concentration of the solution because it affects the amount of PA6 in the CF tow and the remaining calcium chloride.