Layer-Based Stress-Guided Continuous Fibre Path Generation for Additively Manufactured Three-Dimensional Composite Structures

Lightweight structural components with high stiffness-to-mass ratios are of primary interest in advanced aerospace applications, with potential relevance to hypersonic and space vehicle systems. In this context, continuous fibre additive manufacturing offers the possibility of producing load-tailored composite structures by controlling the local reinforcement paths during deposition. However, conventional printing strategies generally rely on predefined patterns repeated through the thickness and do not account for variations in geometry and stress state within three-dimensional components. This work presents a layer-based procedure for the generation of manufacturable continuous fibre paths in three-dimensional composite structures. Starting from the stress field obtained from a preliminary finite element analysis, the structure is sliced along the stacking direction and each layer is processed independently on its corresponding two-dimensional mid-plane section. Principal stress directions are used to generate streamline-based trajectories, which are subsequently combined with boundary-following and filling paths. Selected transverse reinforcement layers can also be introduced to reduce the excessive directionality of a purely stress-aligned architecture. The generated trajectories are finally used to reconstruct an equivalent finite element model with locally anisotropic properties. The procedure is applied to a three-dimensional tensile bracket characterized by a non-prismatic thickness distribution. The generated 3D-printable composite configuration is numerically compared with an AA 2024 reference structure. The results show negligible changes in global stiffness, with a variation of approximately 0.2%, together with a mass reduction of 49.6% and an increase in specific stiffness of approximately 99.0%. These results highlight the potential of the proposed approach for the design of lightweight, load-tailored continuous fibre composite structures for high-performance aerospace applications.