Study of Manufacturing Defects and Tool Geometry Optimisation for Multi-Material Stack Drilling

Abstract

In the aeronautic industries, composite materials are increasingly being used for structural parts. Carbon Fibre Reinforced Plastics (CFRP) are often used in combination with metallic materials, mostly aluminium alloys. This raises new problems in aircraft assembly when it comes to machining the holes for thousands of fasteners. The preferred method for this is a one-shot drilling-reaming-countersinking operation usually using a power tool and with the need to respect tight dimensional and geometric specifications. The solutions proposed so far with existing cutting tools, involving reduced feed rate, are unsatisfactory from an economic point of view. This study first focuses on identifying machining defects and difficulties encountered during drilling of aluminium/CFRP stacks. Then, based on the results of different works on drilling [1,3], an experimental study is proposed to define the critical macro-and micro-geometric parameters of a carbide drill. The criteria relate to the fragmentation of the metallic chips, burr avoidance and zero damage to the CFRP. The first results obtained with the new generation cutters developed show the importance of a constant axial rake angle and of the tool point angle in the chip fragmentation phenomenon but also in preserving the health of the CFRP material. The influence of the constant rake angle on the axial forces generated is also shown. Finally, an optimal combination of the tool geometrical parameters is achieved in order to obtain the expected results.

Evaluation of the performance of coated and uncoated carbide tools in drilling thick CFRP/aluminium alloy stacks

“…This stability was also observed by Benezech et al [17]. It can also be seen that the diameter of the holes drilled in CFRP (H1 and H2 in Fig.…”

“…11. With a similar drill diameter, different results were obtained by Benezech et al [17] where the diameter difference was nearly 30 μm.…”

An experimental study on drilling of unidirectional GLARE fibre metal laminates

“…The stacking sequence investigation usually involved placing the composite sample either between two different types of metals such as titanium and aluminium [9,10], or on the top of a metallic sample [11][12][13][14][15][16] as depicted in Figure 2. This helped reducing the peel up and push out delamination when drilling composites [9], and in some singular cases placing the composite beneath the metal sheet [17].…”

“…The aim of these studies was to optimise the drilling process and evaluate the hole quality for the different materials [10,[14][15][16][17][18]. Some studies have also looked into the effect of the cutting tool types, their geometry and the coating influence on its tool life [10-12, 15, 16, 18, 19]; other studies investigated the effect of using coolants supplied internally through the cutting tool or externally through a nozzle [9,16,20].…”

Modelling the vibration-assisted drilling process: identification of influential phenomena

“…To respond to this issue, solutions have been developed to ensure chip breakage. Benezech et al [1] worked on the development of tools with a specific chipbreaker geometry. Brinksmier et al [2] recommend the use of special coatings on drills and high-pressure lubrication.…”