The drilling of CFRP and Ti6Al4V stacks an innovative approach

The thesis deals the problems about the drilling focusing the experimental investigation on the drilling of Carbon Fibers Renforce Plastics and titanium stacks using tungsten carbide tools in cobalt matrix (WC-Co) coated with Diamond Like Carbon (DLC) and uncoated. It is an experimental campaign divided into two phases in order to define the optimal performance in terms of forces and torque and quality of the hole analyzing diameter measurements, delamination, pull-out and height of burr was performed. In the first phase drilling strategy, influence of process parameters and cooling conditions were investigated on the wear of the tools and the quality of holes. An innovative cooling method has been analyzed: cryogenic cooling using the liquid nitrogen (LN2) as refrigerant element compared to conventional lubricating-cooling method. In the second phase has been completed a drilling campaign using the optimal drilling conditions defined in the previous phase. Objective of the latter phase was to define the hole number of best quality realized with tools made with different grain size WC grains uncoated and coated.