Hybrid Composite Reinforcement Strategies for Large-Scale FDM Additive Manufacturing

Hybrid Composite Reinforcement Strategies for Large-Scale FDM Additive Manufacturing The rapid growth of the 3D printing has opened new possibilities to fabricate structural components through large scale additive manufacturing. The primary aim of this thesis is to address one of the most important challenges in Fused Filament Fabrication (FFF): poor interlayer bonding, which often leads to weak mechanical properties, especially in perpendicular direction to the printed layers. The other goal is to investigate reinforcing strategies that enhance the feasibility of utilizing 3D-printed components in structural applications, such as small-scale pedestrian bridges. Different hybrid reinforcement strategies were conducted to improve the quality of 3D printed component. steps like annealing in 100 degree c for different amount of times, foam filling the cavities, laminate the beam by using GFRP sheets to reach high stiffness. For the 3D printed part, the gyroid Triply Periodic Minimal Surfaces (TPMS) structure was utilized, renowned for its high strength-to-weight ratio. The material used was polylactic acid (PLA) reinforced with chopped carbon fibers for enhanced strength. Different hybrid reinforcement strategies were employed to enhance the quality of 3D printed components. Steps include annealing at a temperature higher than the glass transition temperature (Tg) and lower than the deflection temperature (Td) for different amounts of time, filling the cavities with foam, and laminating the beam using GFRP sheets to achieve high stiffness. After taking these steps, the beams were divided into three sections: Core only (C), Core foam-filled (CFF), and Core foam-filled laminated (CFL) to understand the effect of foam filling and GFRP lamination on the load-bearing capacity of the 3D printed beam. The results showed that foam filling improved the flexural rigidity and failure resistance of the printed structures without adding a considerable amount of weight. The foam interacts with the gyroid Core, distributing the load more evenly, increasing energy absorption, and stabilizing the thin walls of the polymer to avoid early failure. Additionally, it can provide a more common area between the beam and GFRP sheets, ensuring better bonding quality to avoid delamination. The glass fiber sheets laminated specimens showed 5 times more stiffness than foam-filled components, which makes them a good potential candidate for use in civil engineering applications. This research contributes to a deeper understanding of AM structures and presents foam filling as a practical solution to one of the key mechanical limitations in large-scale 3D printing. The insights gained offer valuable guidance for designers and engineers seeking to implement polymer-based additive manufacturing in structural applications. However, research on this topic is limited and can be further explored.