Tool wear and induced damage in CFRP drilling with step and double point angle drill bits

Drilling operations on Carbon Fiber Reinforced Plastics (CFRP) have become crucial for the manufacturing process of multiple components on the aerospace industry. The main objective of this research is to develop a comparative analysis between a step geometry drill bit, currently used in the aerospace industry for drilling processes in CFRP with a hole diameter of 9.54 mm, and the double point angle geometry. The tool material is tungsten carbide with a diamond coating. The performance of each cutting geometry is assessed based on the type of tool wear, the evolution of the thrust force and cutting torque and the onset of machining induced damage on the test specimens. Although the main wear mechanism suffered by both tools was very similar, it was observed a remarkable influence of the cutting geometry on the tool wear evolution and the associated thrust force. This different performance also affected the onset of the machining induced damage.The authors acknowledge the financial support of Airbus Defense and Space through the project Drilling Processes Improvement for Multi Material CFRP-Al-Ti Stacks, and the Ministry of Economy and Competitiveness of Spain through a grant with reference PTA2015-10741-I and project DPI2017-89197-C2-1-R