Modeling and experimental investigation of fiber orientation in cast and 3D-printed cementitious composites

Fiber orientation is process-related and has significant impacts on material performance. However, existing studies only consider the impact of individual factors on the fiber orientation, either boundary impacts or flow field impacts. This work aims to study fiber orientation by considering the combined impact of these two factors. Analytical models were first constructed, which revealed that when the flow of material is negligible, fiber orientation is impacted by the boundary conditions. When the flow field is non-negligible, fiber orientation is affected by the direction of flow streamlines. Specimens were then prepared using fluorescence image processing and μ-computed tomography scanning for fiber orientation analysis. The results indicate that fiber orientation could be controlled by varying boundary constraints and flow fields. Mechanical results reveal that when the designed condition achieves directional-orientated fibers, the mechanical property of specimens could be enhanced with the applied stress direction being the same as the fiber orientation. This work provides a novel insight to tailor fiber-reinforced cementitious material properties by designing the boundary constraints and flow fields in the cast and printing processes.