The effect of peel ply layer on hole integrity when drilling carbon fibre-reinforced plastic

Fibre/matrix delamination is a common problem when cutting carbon fibre-reinforced plastic (CFRP) that can have a detrimental effect on workpiece mechanical properties and hence compromise the in-service performance of the composite part. The present paper details experimental results when drilling small holes (1.5 mm diameter) through backed and un-backed CFRP laminates using tungsten carbide twist drills to determine the effect of peel ply layers (similar to 100 mu m thick nylon sheet attached on both sides of 3 mm thick laminates) on hole entry and exit delamination. Considerable reduction in damage relating to fuzzing, spalling, edge chipping, and delamination was observed when drilling the nylon-backed CFRP material, with scanning electron micrographs showing significantly inferior hole quality for the corresponding un-backed workpieces, particularly at hole exit.