Biaxial fiber reinforcement and bio-inspired woven junctions for high-performance 3D printed topology-optimized CFRP composite structures

Combining topology optimization with continuous fiber 3D printing offers a promising route to lightweight design of continuous fiber-reinforced polymer (CFRP) composites. However, conventional methods aligning fibers with principal stresses often cause fiber discontinuities and stress mismatches at biaxial junctions, limiting overall structural integrity. In biological junctions such as wood branches and bamboo nodes, fibers provide superior strength and toughness through interwoven and interlocking arrangements. This study proposes a synergistic framework for the design and fabrication of CFRP structures. The framework integrates dual-stress-driven Solid Orthotropic Material with Penalization (SOMP) topology optimization, stress-guided structural decomposition and path reorganization, and a bio-inspired woven junction printing strategy. By matching biaxial stresses, orthogonal fiber orientations are assigned and converted into manufacturable continuous toolpaths. At junctions, the bio-inspired sinusoidal woven fibers create macroscale interweaving with microscale interlocks. These features enhance stress transfer and shear resistance. The effectiveness of the framework was validated using the Messerschmitt-Bölkow-Blohm (MBB) beam. Compared with the non-crossing SOMP-optimized MBB baseline, the laminated orthogonal junctions increased the specific load and specific stiffness by 46.18% and 37.14%, respectively. Bio-inspired woven junctions achieved superior enhancements of 96.04% and 68.27%. Strain and failure analyses revealed that the woven bundle interlocks establish stress-transfer pathways. This mechanism reduces stress concentrations and prevents junction delamination and fracture. Overall, this framework provides a practical design-to-manufacture route for high-performance 3D printed CFRP composite structures.