Erosion Behaviour of Stitched Composite Laminates

The sand-water erosion behaviour of notched holes in glass/epoxy composites was investigated. Using tnrough-the-thickness stitching, the amount of hole damage caused by impact testing prior to wear tests was varied. Erosion resistance was evaluated based on the amount of mass loss. Results showed that the holes in unstitched laminate which incurred greatest impact damage, eroded the least. The holes in stitched laminates, however, were more susceptible to erosive wear even though the internal damage appeared less severe. SEM photographs showed that the lower half of the holes in the unstitched laminates remained intact while those in the stitched laminates were eroded substantially. Cut sections away from the hole were observed with an optical microscope. A comparison of cut sections showed that heavy stitching results in severe fibre impalement damage, thereby reducing the reinforcing capability of the fibres around the hole. For the unstitched composite, in spite of more widespread delamination damage, the inherent presence of protruding fibres in the backplies provided additional resistance against erosion.