Ultrasonic‐Assisted Additive Manufacturing of Continuous Aramid Fiber Reinforced Nylon 12 Composites

ABSTRACT Continuous fiber‐reinforced thermoplastic composites (CFRTPs) have been limited by issues such as insufficient fiber–matrix bonding and high porosity, hindering performance enhancement. This study proposed a low‐cost, high‐efficiency ultrasonic‐assisted printing (3DUAP) method. Multistage fiber‐spreading filament‐forming equipment was employed to prepare CAF/PA12 filaments with approximately 60 vol% fiber content. The effects of mold temperature, initial fiber‐spreading tension, and traction speed on filament impregnation degree and mechanical properties were investigated. The prepared 3840D filament achieved 1664.25 MPa tensile strength. An ultrasonic‐assisted additive manufacturing 3D printer was designed to investigate the effects of ultrasonic power and pressure on mechanical properties and surface precision of CAF/PA12 composites. Results showed that 3DUAP specimens exhibited maximum tensile strengths and tensile modulus of 1085.14 MPa and 32.79 GPa, respectively. Specimen porosity decreased to 1.85%. With increasing ultrasonic power and pressure, the tensile strength of both specimens first increased then decreased, while surface roughness values first decreased then increased. The high temperatures generated by the ultrasonic device's high‐frequency vibration promoted the impregnation of the printed filament, enhancing the fiber–resin interfacial bonding strength. Simultaneously, it strengthened the interlaminar and intertrack bonding while reducing porosity in the printed specimens. This process achieved the printing of high‐fiber content, high‐performance CFRTPs, providing a technical reference for the additive manufacturing of high‐performance composites.