Tribo-functional design of double cone drill implications in tool wear during drilling of copper mesh/CFRP/woven ply

This article presents an experimental analysis of drilling using carbide drills on carbon fiber reinforced plastic (CFRP) laminates specially made with copper mesh on one side and woven carbon fabric on the other side using carbide drills. The objective of this study was to improve the machining performance during drilling of sandwiched composite using various dimensions of double cone drill. The drill design in terms of its tribological characteristics (i.e. friction, wear) are analyzed including cutting force, life, chip form and hole quality. Results have shown that double cone drills generated less thrust force compared to standard twist drills. No delamination was found in the holes at high feed rates (above 0.1 mm/rev). This could be attributed to the presence of thermoplastic nodules between the layers of the CFRP laminate and the presence of woven fabric ply at the bottom of the laminate. Furthermore a relationship between the feed per cutting edge and the thickness of the thermoplastic layer has been developed to promote the formation of continuous chips during drilling. Finally, SEM observations reveal several damage when standard twist drills were used and less damage was observed with double cone drills. These damaged areas were observed in the plies of fibers oriented at −45° and 90° compared with peripheral cutting speed of the drill.