Effects of inter-fibre spacing and matrix cracks on stress amplification factors in carbon-fibre/epoxy matrix composites, Part II: Hexagonal array of fibres

The fibre volume fraction plays a key role in determining the strength of carbon-fibre/epoxy composites. In this study the effect of fibre volume fraction for a hexagonal packing arrangement, which is considered the most ‘efficient’ arrangement, was investigated using three-dimensional elasto-plastic finite element (FE) analysis. The stress amplification factors (SAF) in intact fibres adjacent to a fractured fibre was calculated both with and without a conical-shaped matrix crack. The FE results show that SAF’s in the hexagonal array are much lower than in a planar array with the same R/d ratio. The inclusion of a conical-shaped matrix crack was found to have less effect on the SAF than in a composite with a planar array of fibres.