Innovative integration of digital light processing and direct ink writing for continuous fiber reinforced photopolymer

Abstract Continuous fiber has been widely used in Additive Manufacturing (AM) to reinforce polymers. However, it has been challenging to 3D print fully dense composites with arbitrary fiber placement. Filling the gaps between fibers is difficult for extrusion‐based processes like fused filament fabrication and Direct Ink Writing (DIW). This study explores the integration of Digital Light Processing (DLP) and Direct Ink Writing technologies to enhance the fabrication of continuous fiber‐reinforced photopolymer (CFRP) composites. The unique combination of these AM techniques aims to improve the mechanical properties of composites by eliminating the gaps between fibers and increasing the interfacial bonding strength. A custom‐built hybrid manufacturing system was employed, allowing for precise control over both DLP and DIW processes. The material composition and curing strategy were explored to improve the printing quality of continuous fibers in photopolymer. Experiments were conducted to assess the mechanical performance of CFRP composites. Results indicate that the integration of DIW and DLP generally improves Young's modulus and flexural modulus of fiber‐reinforced resin, with some cases closely matching theoretical predictions, though certain results show a lower modulus than expected. The fracture surfaces were also investigated. It was found that broken fibers are not uniform, which suggests that the resin infiltration into the fiber bundle can be improved. Highlights Hybrid DLP and DIW system for continuous fiber‐reinforced photopolymer composites. Improved mechanical properties by reducing fiber gaps, stronger interfacial bonding. Higher stiffness and strength achieved, addressing fiber crowding and resin infiltration. Material properties enhanced using nanopowder additives for superior performance. Adaptive UV curing ensures efficient and uniform omnidirectional polymerization.