Machinability study of uncoated and coated carbide tools when drilling CFRP/metal stacks

Abstract

Carbon fiber reinforced plastic (CFRP) composite is often used in combination with other materials, requiring it to be machined during fabrication of a structure. In the aerospace industry, CFRPs are often stacked together with metals to provide stronger and better performance of aircraft structural components with the advantage of weight reduction and increasing mechanical strength. Drilling which is the most common machining process of CFRP is complex and often results in delamination of the composites. This study presents the findings of an experimental investigation in drilling of CFRP plate stacked on top of Aluminum 2024 plate. Uncoated carbide and TiAlN coated carbide tool were used to perform the drilling of the CFRP/aluminum stack at cutting speeds of 70, 85, 100 mm/min with constant feed rate of 0.1 mm/rev using dry drilling. The responses that were analyzed include thrust force, torque, hole quality, CFRP surface delamination, and tool wear. Experimental results showed that the application of various cutting speeds have no significant effect on all the responses analyzed when drilling CFRP/aluminum stacks for both tools. In terms of hole quality and CFRP surface delamination, the uncoated tool displayed better results compared to coated tool at cutting speeds of 85 and 100m/min. This is due to the sharp cutting edge of the uncoated tool that enabled efficient cutting in producing holes. Experimental results also showed that coated tool performed better than uncoated tool producing lower thrust force and torque, lower surface roughness, and lower tool wear rate.