Drilling of Multi-Layer Composite Materials consisting of Carbon Fiber Reinforced Plastics (CFRP), Titanium and Aluminum Alloys

In this paper results are presented concerning the realization of economical drilling processes of multi-layer materials. Different carbide drill designs with improved geometries and coatings were investigated and compared by characterizing the cutting forces, tool wear, hole quality, and chip formation. Investigations have shown that dry machining of titanium workpiece layers leads to increased tool wear, chip formation problems, and surface damage in the aluminum and CFRP-layers. Consequently, the drilling experiments were carried out with minimum quantity lubrication (MQL) using different cutting fluids and supply strategies. The investigations were mainly focused on the development of the optimum drilling condition with respect to tool shape, tool material, and machining parameters. Another objective of the investigations was to analyze surface defects of the hole and the resulting diameter tolerances due to the high mechanical and thermal loads when machining titanium.