Effect of stitches on the impact behaviour of graphite/epoxy composites

Low-velocity impact tests were carried out on stitched carbon fibre-reinforced plastic laminates of various thicknesses, whose behaviour was studied with reference to the overall force–displacement curve, first failure load, penetration, indentation and damage extent. The results obtained were compared with similar data available for 2D laminates. Apparently, the presence of stitches did not affect substantially the material behaviour in terms of force–displacement curve, first failure load, and indentation. However, the stitched laminates exhibited a penetration energy about 30% lower than their 2D equivalent. Further, the advantage of stitching in terms of impact damage resistance was evident only for high thickness composites. The data generated suggest that the use of stitches could be unnecessary to hinder delamination in thin 2D laminates.