Comprehensive investigation of cutting mechanisms and hole quality in dry drilling woven aramid fibre–reinforced plastic with typical tools

Due to high specific strength and strong toughness, aramid fibre–reinforced plastics have been widely used in the aircraft, military, and automobile industries. However, in the hole-making process, these excellent properties make aramid fibre–reinforced plastics difficult to machine and prone to severe entrance and exit damages. In this article, the cutting mechanisms of three typical tools (twist drill, burr tool, and brad drill) are thoroughly investigated during dry drilling of aramid fibre–reinforced plastic. On this basis, systematic experiments are conducted to evaluate the cutting performance and hole quality. At the hole entrance, the cutting edges of the twist drill peel and tear the uncut material, which results in severe fuzzing damage. Due to the radial rake angles of the burr tool and brad drill, the radial component of the cutting force can pre-tension aramid fibres prior to being cut, which effectively reduces the fuzzing defect. At the hole exit, the extrusion action of the chisel edge and the severe chip adherence are the main causes of exit damage for the twist drill and burr tool, respectively. Due to the decrease in the thrust force and improvement in the shearing action, the best hole quality is achieved by the brad drill. To further improve the hole quality, an auxiliary approach using collars is introduced to effectively restrain the damage by enhancing interfacial bonding strength. This article provides comprehensive and available information on tool performance for drilling aramid fibre–reinforced plastics, which can help guide process optimizations to achieve the desired hole quality.