Drilling of Carbon Fibre Reinforced Plastic Composites

Following an extensive literature survey focusing on the machinability of carbon fibre reinforced plastics (CFRP), three main phases of experimental work were undertaken to evaluate the drilling of CFRP and associated stack materials. Phase 1 and 2 involved small diameter holes (1.5 mm) in thin CFRP laminates (3 mm thick) while Phase 3 addressed the feasibility of one-shot drilling (6.35 mm diameter holes) in multilayer workpiece stacks comprising titanium, CFRP and aluminium. Machinability was assessed in terms of tool life/wear, force/torque, hole size and geometrical accuracy, workpiece surface integrity and chip morphology. Initial trials (Phase 1A) were performed to investigate the effect of peel ply layers (~100 ¿m thick nylon sheet attached on both sides of the laminate to assist the bleeding of volatiles and air during curing as well as preventing surface contamination) on hole entry and exit quality, as current industrial practice involves removal of the protective sheet prior to drilling.