Effect of fiber length on the tensile strength of unidirectionally arrayed chopped strands

Abstract

This study investigates the effect of fiber length on the tensile strength for discontinuous fiber composites. A composite with a staggered structure of fiber bundles were prepared by stacking prepreg sheets with unidirectionally arrayed chopped strands with a predetermined fiber length. The sheets were prepared by introducing fine slits at regular intervals along the fiber direction. The final failure is caused by an unstable growth of delamination from the tip of the bundles. The conventional linear fracture mechanics model cannot explain the reduction in the tensile strength as the fiber length shortens. Consequently, this paper proposes a novel fracture mechanics model that considers a non-linear stress–strain relation for the composite, which incorporates varying fiber length. The results confirm that this model can explain the relation between the tensile strength and fiber length very well, without any fitting parameters.