Assessment of hole quality and thrust force when drilling CFRP/AL stack using carbide tools

Abstract

Drilling composite materials is challenging due to the anisotropic and non-homogenous structure of composites. In fabrication works, metals are joined to composites to form a hybrid strengthened structures, and this posed a great problem during drilling, due to the dissimilar drilling conditions for each material and also sharp metal chips effect on the quality of hole on composite plates. This paper evaluates the experimental results on the machining performance of coated and uncoated 4 facet carbide drills when dry drilling stack of carbon fiber reinforced plastic (CFRP) and aluminum. Drilling trials were carried out on CFRP/Al2024/CFRP stack at constant cutting speed of 37 m/min with three feed rates within 0.03-0.25 mm/rev. Results revealed that 4 facet coated drills performed better than uncoated drills in terms of delamination. It was found that hole entry delamination increases with increasing feed rate, however uncut fibers which were dominant at low feeds on hole exit, disappears with increasing feed rate. It was also found that thrust force for coated tools were quite higher than uncoated tools.