Effect of fiber length in extruded and cast cement composites

The influence of fiber length on tension and flexural behavior of extruded and cast cement composites was examined for PVA (hydrophilic) fibers and polypropylene (hydrophobic) fibers. The fiber-matrix interface, fiber surface, and microstructure of the composite cross-section were characterized by SEM. Opposite trends were obtained for the cast and extruded composites with increasing fiber length. For the extruded composites, decreasing fiber length increased flexural and tensile response, whereas for the cast composites increasing the fiber length increased the flexural and tensile response. These differences were found to be a result of differences in fiber-matrix bond properties and fiber distribution. The extruded composites showed a stronger fiber-matrix bond compared to the cast composites. This led to differences in the fiber failure mechanism: fiber rupture of the 6mm fibers in the extruded composite, and fiber pullout of both fiber lengths in the cast composites and for the 2mm fibers in the extruded composites.