Influence of overlap rate and ultrasonic compaction on mechanical performance for additive manufacturing of continuous carbon fiber reinforced polylactic acid composites

•A continuous fiber printing structural model with overlap rate is established.•The effect of overlap rate on the printing performance is identified.•Proper overlap state between filaments is beneficial for the mechanical properties.•Ultrasonic compaction demonstrates favorable adaptability to the overlap rate. The additive manufacturing (AM) technology of continuous fiber reinforced thermoplastic composites (CFRTPCs) is gaining attention in the composites industry due to its excellent mechanical performance, potential designability and light-weight structures. Process parameters of AM have a significant impact on mechanical performance and forming accuracy. There is still a Lack of clear design basis for hatch spacing as structural parameter. This study focused on the effect of overlap rate on AM performance of continuous carbon fiber (CCF)/polylactic acid (PLA) composites through the mechanical test, surface morphology, defects characterization and failure analysis, and investigated the adaptability of ultrasonic compaction post-treatment to overlap rate settings. The results indicated that proper overlap state between filaments was beneficial for mechanical properties. The optimal interlaminar shear strength (ILSS) increased to 22.72 MPa by 56 % and tensile strength improved by 17.5 % to 721.65 MPa at various overlap rates. Surface roughness remained stable at approximately 33 μm. Ultrasonic compaction achieved a maximum ILSS up to 24.84 MPa with improvement of 10.26 %, and tensile strength reached to 736.76 MPa with 2.09 % improvement, showing excellent adaptability to overlap rate design. Research findings will improve understanding of digital adjustment mechanisms for printing parameters and provide design guidance for high-performance AM technology of CFRTPCs.