Topology optimization and continuous path strategy for 3D printed continuous fiber composite structures

The structure of 3D printed continuous fiber-reinforced thermoplastic composites (CFRTPCs) exhibits distinct multi-scale features of micro fiber pathways and macro structure. In this work, a new multi-scale optimization method for the macroscopic configuration and fiber orientation of composite material structures with fiber-sensitive filter is introduced, and a continuous path planning method based on flow field theory and Euler path theory is proposed to achieve fully continuous and uninterrupted fiber path planning. Compared with the unidirectional fiber Messerschmitt-Bölkow-Blohm (MBB) beam structure, the stiffness of the multi-scale MBB structure with optimized fiber direction has increased by 42.58%. The path planning method proposed in this work greatly improves fiber continuity, mechanical and printing efficiency, and simplifies the printing process of additive manufacturing CFRTPC structures, which provides the possibility for additive manufacturing of complex load-bearing CFRTPC structures. Highlights: Fiber sensitive filter is used to realize the smooth transition of the fiber in the discrete unit. Streamline and Euler path theory applied to print path planning The method realizes the continuous fiber printing path without fiber cutting. The mechanical properties of optimized design have obvious advantages.