Big Area Additive Manufacturing of Fiber Composites

This thesis explores the potential of wet-on-wet, material extrusion additive manufacturing (MEX-AM) using thermoset polymers, with a particular focus on improving surface quality and achieving subvoxel control of fiber orientation. The research is motivated by the desire to expand the functional and structural capabilities of big area additive manufacturing (BAAM), while also investigating its applicability in complex concrete formwork construction.

The work is divided into three core focus areas. First, the surface quality of printed thermoset strands was examined, with a goal of minimising post-processing requirements. Strategies such as nozzle geometry modification, vertical toolpath optimisation, and controlled over-extrusion were investigated. It was found that specific nozzle designs, particularly those incorporating trapezoidal side wings, combined with tailored layer heights and extrusion parameters, significantly improved surface flatness and stability.

Second,thethesisaddressesthechallengeofcontrollingfiberorientationwithintheprinted strands. Both conventional parameter-based alignment and novel methods involving multidirectional shearing, achieved through rotational and inclined nozzle movements, were tested. The research demonstrated that fiber orientation could be precisely manipulated across all three spatial dimensions, allowing the creation of programmable anisotropic material behaviour. These microstructures were shown to influence both thermal conductivity and mechanical strain response, offering new possibilities for the design of functional composite materials.

Finally, the practical implementation of thermoset 3D printing in concrete construction was explored through two approaches to the manufacturing of formwork for concrete castings. A hybrid method was developed, combining thermoset coating with pre-milled Polystyrene foam to create reusable, high-precision formwork. Additionally, free-standing formwork structures were printed entirely from thermoset material and evaluated through casting trials of complex concrete columns. These tests confirmed the mechanical reliability, reusability, and geometric fidelity of the printed formworks, while also identifying areas for future optimisation, such as fiber reinforcement and recycling strategies.

Overall, the results of this thesis demonstrate the viability of thermoset additive manufacturing for producing both performance-driven composites and functionally robust architectural elements. By uniting material innovation with additive manufacturing, this work contributes to the development of more adaptable, efficient, and sustainable manufacturing processes.