Investigations on Drilling of Al/CFRP/Ti Stacks Using Micro Grooved Drills

This paper presents a comprehensive study of the drilling of hybrid Al/CFRP/Ti stacks, which is a critical operation in the assembly of aerospace structures. The intricate amalgamation of aluminum alloy, carbon fiber reinforced polymer (CFRP), and titanium alloy in the stack introduces complex material interactions during drilling. The current work is aimed at evaluating and comparing the surface quality of the Al/CFRP/Ti stack holes drilled by standard and micro-grooved drills under minimum quantity lubrication (MQL) conditions. The experimental investigation is carried out by varying cutting parameters such as cutting speed and feed. In this study the influence of the machining parameters and tool geometry (drilling with micro-grooved and standard drills) on thrust force and torque under MQL conditions have been investigated. Furthermore, the substantial impact of thrust force variations resulting from diverse material stacking on the surface quality (delamination of CFRP, surface roughness) of the holes is highlighted. Circularity characteristics and hole diameter errors are also scrutinized for both drills. The findings offer valuable insights for optimizing the drilling of hybrid Al/CFRP/Ti stacks across industries that demand advanced materials and machining techniques.