New Compound Drill Bit for Damage Reduction in Drilling CFRP
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This paper focuses on finding a suitable drill bit for drilling Carbon Fiber Reinforced Plastic (CFRP). The drilling characteristics of the dagger drill, the double point angle drill, and the candle stick drill are studied. The results show that the side edge has poor ability to remove burrs, and the tip structure of the outer corner of the candle stick drill can greatly reduce the entry damage. However, the outer corner small tip structure of the candle stick drill cannot effectively remove the uncut fiber around θ = 0° of hole exit. The long secondary cutting edge of the dagger drill makes a small thrust force at the drilling exit stage and reduces the dropping speed of the thrust force, leading a lower impact on the laminate bottom. Then, a new tool is developed for drilling CFRP based on the advantages of the three kinds of drill bits. The drill has a long secondary cutting edge, a small tip diameter and a small tip structure of the outer corner. And its drilling characteristics are analyzed. The result shows that the new compound drill bit can effectively remove fibers and reduce thrust force at the drilling exit stage, form burr-free and small delamination hole. The drill reduces the waste of CFRP in manufacturing process since the exit damage is reduced substantially, which is in line with the concept of green manufacturing.
KeywordsDrilling CFRP Compound drill bit Damage reduction Drill structure
List of Symbols
The angle between the cutting speed and the fiber direction
The work is supported by the National Natural Science Foundation of China (Nos. 51775184, 51275168 and 51605161).