Experimental Study on Hole-making of CFRP by PCD Tool under Cryogenic Cooling and Dry Machining Conditions

Experimental studies on hole-making with PCD tools under carbon dioxide cryogenic cooling and dry conditions were carried out for carbon fiber reinforced polymer (CFRP) to improve the cutting performance, hole-making accuracy and hole-making quality of CFRP materials. Under conventional and cryogenic cooling-assisted drilling conditions, conventional polycrystalline diamond tools and surface textured tools were used to carry out experimental studies on hole-making of CFRP materials, and to analyze the differences in thrust force, total cutting force, entrance diameter and relative error, tool surface adhesion, hole wall morphology and defects with different cutting parameters. Under dry and cryogenic cooling conditions, both the thrust force and the total cutting force generated by the drilling process of the composite increased continuously with the increase of the feed rate. When the feed rate increased, the relative error range of the entrance diameters obtained by the PCD tool with dry drilling, the PCD tool with cryogenic cooling and the textured PCD tool with cryogenic cooling were 0.29%-0.42%, 0.57%-1.15% and 0.38%-0.89% respectively under the test conditions. Compared with dry machining, there was almost no chips adhesion on the rake face of the tool under cryogenic cooling conditions. In general, it could be observed that there were some obvious fiber breakage, more fiber fracture pits, and the phenomenon of micro-cracks and uneven matrix smearing on the surface of inner hole wall under cryogenic cooling conditions. During the process of drilling CFRP, the increase in feed rate increased the cutting layer area, which lead to a constant increase in thrust and total cutting forces. It was found that the bigger thrust and total cutting forces could be obtained under cryogenic cooling conditions compared with the dry drilling at the same cutting parameters. Under the test conditions, compared with the cryogenic cooling method, the use of dry drilling could improve the hole-making accuracy of the entrance diameter size, while the cryogenic cooling way could effectively reduce the chips adhesion on the rake face of the tool and improve the anti-adhesion effect. It was found that a flatter and more uniform surface of the hole wall could be obtained by the dry hole-making at the same cutting parameters, and the inner hole wall had the poor poorer machining defects under cryogenic cooling conditions as a whole. It is of great research significance to carry out efficient and low-damage hole-making technology of the composites to reduce tool wear, improve hole-making efficiency, hole-making accuracy and realize low-defect machining. Existing research on the cutting tool development and process innovation in machining of the carbon fiber reinforced polymer is still in the experimental exploration stage, as a result, it is necessary to carry out deeper research and explore how to achieve high performance hole-making through the comprehensive innovation involving the tool design, cutting process and cooling conditions and other aspects, which can contribute to providing a new idea and a new way for high-performance key machining process technology of the hole-making of the high-end composite components. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.