Additive Manufacturing With Continuous Fiber: A Comparison Between Prepreg and In-Situ Impregnated Fiber on Printing Accuracy, Bonding, and Mechanical Performance

Abstract Continuous fiber-reinforced composites are widely used in aerospace, sports, and energy industries due to their lightweight, high stiffness, and strength. Traditional manufacturing methods for these composites are costly and result in uniform fiber directions. Additive manufacturing, particularly material extrusion, offers a cost-effective alternative for complex shapes, allowing greater freedom in fiber distribution and orientation, thus exploiting fiber anisotropy. Most commercial printers use prepreg fiber for its superior bonding with the matrix and low void content. However, its production involves matrix impregnation, increasing bending stiffness and stress during printing. Conversely, dry fiber and in-situ impregnation systems are favored in research for their ease of construction and fiber deformability. Dry fiber undergoes short-term impregnation in the printer nozzle, reducing stress but compromising bonding quality. Despite their respective advantages, a comprehensive comparison of printed fiber configurations, path accuracy, layer bonding, and mechanical properties for these fibers is lacking. This paper addresses this gap by constructing an in-situ impregnation printer for dry fiber and using the Anisoprint Composer A4 for prepreg fiber, ensuring identical material properties and printing parameters. The study evaluates printing quality through a rich curvature path with varying radii, assessing accuracy via Hausdorff distance and examining layer bonding and fiber configuration using SEM. Mechanical performance is tested with tensile and three-point bending tests on specimens with uni-directional fiber distributions. The tensile test assesses stiffness and strength, while the bending test evaluates inter-layer bonding. The comparative analysis reveals detailed insights into the printing quality and mechanical performance of both fiber types. The key finding is that dry fibers with in-situ impregnation excel at maintaining ideal printing shapes, although their impregnation with the matrix can be poor and introduces defects that reduce product performance. This trade-off provides valuable guidance for fiber and printing system selection in research and industry.