Research on the fabrication of continuous carbon fiber reinforced polyamide 6 composites by means of ultrasonic vibration

Abstract

Abstract Because of the high viscosity and poor fluidity of thermoplastic resin, it is easy to form void in thermoplastic composites fabricated by traditional methods. The introduction of ultrasonic vibration into the fabrication of thermoplastic composites promotes the flow of thermoplastic resin and improve the quality of thermoplastic composites. In this study, continuous carbon fiber reinforced polyamide 6 (CF/PA 6) composites were fabricated by ultrasonic vibration. The effects of ultrasonic amplitude and welding time on the temperature variations of the CF/PA 6 stack during the fabrication process were firstly studied. Meanwhile, the process of impregnation evolution was observed. Then, the quality of CF/PA 6 composites with different ultrasonic vibration parameters were evaluated from the aspects of carbon fiber (CF) fabric structure, carbon fiber diameter, void content, fiber volume fraction, and the flexural strength. The results show that increasing the ultrasonic amplitude and welding time can increase the fiber volume fraction and decrease the void content of CF/PA 6 composites. However, increasing ultrasonic amplitude and welding time result in a smaller carbon fiber diameter and worse CF-PA 6 interface properties. The CF fabric structure is sensitive to ultrasonic vibration parameters. Ultrasonic amplitude and welding time exceeding a certain threshold reduce the flexural strength of CF/PA 6 composites. The flexural strength of the composites is improved by increasing the ultrasonic amplitude and welding time within a limited window. Different from flexural strength, the flexural modulus of the composite increases with the increase of ultrasonic amplitude and welding time due to more compact CF fabrics in the composite laminates. In addition, the failure mode of composites is sensitive to the ultrasonic vibration parameters.