Influence of Controlled Fiber Orientation on the Mechanical and Microstructural Properties of Cellulose Excelsior–Cement Composites

This study investigates the influence of controlled fiber orientation on the mechanical and microstructural properties of cellulose excelsior fiber cementitious composites with an excelsior content of 75% by volume. Two different sets of composites were fabricated. In one set, no effort was made to orient the fibers, while in the other set fibers were preferentially aligned through manual placement and compressive consolidation. The mechanical performance, including elastic modulus and flexural strength, was evaluated. The internal structure, specifically porosity and 3D fiber orientation, was quantified using X-ray Computed Tomography (XCT) and subsequent 3D image analysis. The results demonstrate that the composites with aligned fibers exhibited a 20% higher bulk density and a significantly lower porosity (5.1%) compared to the non-aligned composites (9.0%), representing a 43% reduction in void volume. Further image analysis showed distinct differences in fiber orientation relative to the axis of the specimen. These different distributions led to a 120% increase in elastic modulus and a 58% increase in flexural strength. These results demonstrate how, within limits, the mechanical properties of the composite system can be controlled to meet application demands.