3D reinforced stitched carbon/epoxy laminates made by tailored fibre placement

Tailored fibre placement (TFP) preforms made of carbon fibre were 3D reinforced with aramid, polybenzoxazol (PBO), polyethylene and polyester fibres and vacuum injected with epoxy resin. The effects of stitch distribution and stitching process parameters on Mode I interlaminar fracture toughness were analysed using a statistical approach. Stitch distribution had a minor effect but 3D thread tension had to be carefully chosen to gain optimum mechanical properties. PBO fibre provided the most improvement in fracture toughness. 3D reinforcing with aramid fibre reduced tensile and flexural properties by 3-8%. Low velocity impact damage in TFP was larger than in fabric but smaller than in tape laminates. Compression-after-impact strength was partly increased by 3D reinforcing in some circumstances but no improvement was found under other conditions.