Additively manufactured polymer structures often exhibit strong anisotropies due to their layered composition. Although existing methods in additive manufacturing (AM) for improving the mechanical properties are available, they usually do not eliminate the high degree of structural anisotropy. Existing methods for continuous fiber (cF) reinforcement in AM can significantly increase the mechanical properties in the strand direction, but often do not improve the interlaminar strength between the layers. In addition, it is mostly not possible to deposit cFs three-dimensionally and curved (variable–axial) and, thus, in a path that is suitable for the load case requirements. There is a need for AM methods and design approaches that enable cF reinforcements in a variable–axial way, independently of the AM mounting direction. Therefore, a novel two-stage method is proposed in which the process steps of AM and cF integration are decoupled from each other. This study presents the development and validation of the method. It was first investigated at the specimen level, where a significant improvement in the mechanical properties was achieved compared to unreinforced polymer structures. The Young’s modulus and tensile strength were increased by factors of 9.1 and 2.7, respectively. In addition, the design guidelines were derived based on sample structures, and the feasibility of the method was demonstrated on complex cantilevers.

Large-scale additive manufacturing (LSAM) using fused granulate fabrication (FGF) offers a potential route for the high-value utilization of recycled thermoplastic composites. This study investigated recycled PA6 containing nominally 30 wt.% glass fibers as a candidate feedstock for large-format FGF. An unmodified reference and formulations containing SF315/PTFE, SF315/U15, and MIX-OH were examined. The granulates were characterized using melt mass flow rate measurements, thermogravimetric analysis, and differential scanning calorimetry, while mechanical properties were compared after injection molding and FGF processing. The best FGF performance was obtained for SF315/PTFE (polytetrafluoroethylene) and SF315/U15. Their tensile strengths reached 117.3 and 118.7 MPa, respectively, compared with 56.8 MPa for the FGF-processed reference. Flexural strengths reached 158.8 and 152.4 MPa, respectively, versus 88.0 MPa for the reference. The tensile and flexural improvements produced by MIX-OH after injection molding were not retained after FGF processing, confirming strong processing-route dependence. Preliminary pull-off screening demonstrated that TPU-bonded polymer–steel joints could be produced. Under the investigated conditions, SF315/PTFE and SF315/U15 were identified as promising recycled PA6/GF30 formulations for large-format FGF and further tooling-oriented development.