Process Forces Analysis and a New Feed Control Strategy for Drilling of Unidirectional Carbon Fiber Reinforced Plastics (UD-CFRP)

Abstract

Reliable machining of carbon fiber-reinforced plastics (CFRP) is the key for application of these lightweight materials. Due to its anisotropy, CFRP is a very difficult material to machine because of occurring delamination and fiber-pullouts. The tool design is especially crucial to minimize and to avoid these processing errors. In this paper a process analysis for drilling is shown for better understanding of the chip formation. Drilling of unidirectional CFRP enables the investigation of the effect of fiber orientation on the chip formation process. In theory, the amount of cut fibers and the cutting angle to the main cutting edge determine the cutting force. Experimental tests with varied macroscopic drill geometries verify this theory. Based on these detected relationships, the tool loads can be calculated for a successful tool design.

Experimental Study of Drilling Temperature, Geometrical Errors and Thermal Expansion of Drill on Hole Accuracy When Drilling CFRP/Ti Alloy Stacks

“…The rest is probably influenced by changeable dynamic conditions in the interface zone of the tool-workpiece, vibrations, and inhomogeneous hardness of the alloy. In References [ 16 , 17 , 18 , 19 ] the effect of tool wear on hole diameter was reported. Figure 7 takes the discussed results into consideration.…”

“…Hole quality in CFRP/Ti alloy stack is characterized by the following respond values in Ti: Surface roughness [ 1 ], hole diameter, geometrical accuracy (roundness) [ 2 ], burr size [ 3 ]; and in CFRP by delamination factor ( F d ) [ 4 , 5 ], thermal destruction, and the damage value ( Q d ) [ 6 ]. In experimental studies the most often measured physical quantities are thrust force ( F , N) [ 1 , 5 ], torque ( M c , Nmm) [ 1 , 5 ], cutting temperature (T, °C) [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ], chip formation mechanism [ 14 , 15 ], and technical quantities such as flank wear [ 16 , 17 , 18 ] and tool life [ 19 ]. The abovementioned quantities are commonly used to explain the physical nature of cutting parameters [ 3 ], the tool geometry [ 20 , 21 ], and tool material, as well as the coolant application effect [ 7 , 22 , 23 , 24 ] on the response values.…”

“…Feature research identified that drilling the CFRP/Ti stack with a cutting speed v c = 45 m/min and feed f = 0.09 mm/r via a WC drill with a thickened chisel edge, point angle of 130°, and helix angle of 20° would provide hole a diameter according to H9 and a hole of roundness of 0.015 mm. It was specified that the most significant factors that responded to delamination in CFRP are feed rate [ 19 , 25 , 26 ] and point angle [ 26 , 27 ]. However, the burr size in Ti alloy is mostly affected by the feed rate [ 28 ], tool material [ 29 ], and tool wear [ 17 , 18 ], and it could be reduced by using MQL [ 7 , 24 , 29 ], LN 2 [ 16 , 30 , 31 ], VAD [ 22 ] and UAD [ 10 , 23 ] techniques.…”

Experimental Investigations Towards Hole Accuracy in Micro-drilling of Carbon Fibre Reinforced Polymer Material

“…However, there were particular defects occurred when drilling CFRP material such as delamination and uncut fiber [10], [11]. In addition, the material is hard to drill due to the high structural stiffness of carbon fiber and low thermal conductivity of polymer [12], [13]. Therefore, the hole accuracy and diameter will be affected by this kind of defect.…”