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Drill bit with clip-edges based on the force control model for reducing the CFRP damage

Carbon fiber reinforced plastic composites are popular in the aviation industry, and it is inevitable to drill holes within strict damage tolerances during assembly. However, drilling damages often occur at the drill-exit of carbon fiber reinforced plastic for lacking back support. This paper aims to study the drilling damages formation of carbon fiber reinforced plastic, and further proposes a novel drill structure for reducing the damages. According to the damage formation of drill-exit fibers, the mathematical model is established to analyze the tool-fibers cutting process and fiber deflection. Then based on the cutting model, the multi-edge control force cutting method is proposed, and it is an effective method to cut off fibers with deflection control and damage reduction. In order to carry out the cutting effect, a novel clip-edges drill structure is proposed. The geometric analysis of the novel structure reveals that the structure can cut the fibers from both sides and reduce fiber resin cracking. Finally, comparative experiments are carried out in drilling carbon fiber reinforced plastic, and the novel drill bit with clip-edges drill structure can reduce drilling exit damage and obtain more high-quality holes.