Evaluation of Tools and Cutting Conditions on Carbon Fibre Reinforced Laminates

Abstract

Abstract. The distinctive characteristics of carbon fibre reinforced plastics, like low weight or high specific strength, had broadened their use to new fields. Due to the need of assembly to structures, machining operations like drilling are frequent. In result of composites inhomogeneity, this operation can lead to different damages that reduce mechanical strength of the parts in the connection area. From these damages, delamination is the most severe. A proper choice of tool and cutting parameters can reduce delamination substantially. In this work the results obtained with five different tool geometries are compared. Conclusions show that the choice of an adequate drill can reduce thrust forces, thus delamination damage.

Comparative analysis of drills for composite laminates

“…This drill tip tends to tension the fibers prior to cut, enabling a clean cut. From visual inspection, the holes drilled with this tool always seem smoother and the surface roughness of hole walls is lower, Dura˜o et al 13 Similar conclusions were taken from the remaining spindle speeds.…”

“…Thus, core drill, candle stick drill, saw drill, and step drill can be operated at larger feed rates than twist drill, meaning shorter cycle times, without delamination damage. The influence of tool geometry on delamination was also evaluated in, [13][14][15] showing the benefit of using a step drill. The advantage of pilot hole drilling on delamination reduction by cancelling the chisel edge effect during final diameter machining has been studied by different authors.…”

“…This was an expected outcome, and it is in line with the findings from previous works. [9][10][11][12][13][14][15][16][17][18][19][20]26 Consequently, the differences observed on thrust force results are due to the tool variations, either in terms of the geometry or in terms of the material. From Figure 5, it turns out that WC tools have always smaller thrust forces than polycrystalline diamond tools for all feed rates used in the experimental work.…”