Low velocity impact response of Vectran-stitched composites is investigated experimentally using a Drop Weight Impact machine. Test specimens are stitched with varying stitch densities and stitch thread thicknesses, in order to study the influence of these parameters on the impact response. Visual inspection on damage surface reveals that stitch performs as a crack initiator, as well as a crack arrestor. Longer and denser matrix crack lines are observed in densely stitched composites, compared to isolated matrix crack areas in moderately stitched composites. Ultrasonic C-scan compares effectively the delamination areas and indicates that higher stitch density is more capable of impeding delamination growth by arresting cracks at closer interval. The impact response of load-time and load-deflection plots are studied and analysed. It is found out that the onset of delamination is not influenced by stitch density and stitch thread thickness, but the maximum residual impact force is related to the delamination size of the laminates, which in turns is related indirectly to stitch parameters. Moderately stitched composite laminates are also more flexible than densely stitched ones, mainly attributed to larger delamination area within the impacted laminates. Results have also shown that the influence of stitch density on low-velocity impact damage is more prominent compared to the effect of stitch thread thickness. Energy consumption for the-impact process is finally discussed with the note that, although absorbed energy is independent of stitch density and stitch thread thickness, the proportion of energy consumed for delamination and matrix cracks is different for densely stitched and moderately stitched composite laminates.
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