Abstract

Due to its excellent specific mechanical properties, carbon fibre-reinforced polymer (CFRP) composite is a widely used structural material in the aerospace industry. However, this material is difficult to cut, mainly due to its inhomogeneity and anisotropic features and because of the strong wear effects of its carbon fibres. In the scope of aerospace industrial uses of this material, thousands of holes have to be machined for purposes of assembly. Nevertheless, conventional drilling technology – even if special drilling tools are used – is only moderately able to manufacture good quality holes. Wobble milling is a novel advanced hole-making technology, which has been developed to minimize machining-induced geometrical defects like delamination or uncut fibres. The main objective of the present paper is to compare wobble milling, helical milling and conventional drilling technologies concerning unidirectional CFRPs. In addition, the kinematics of wobble milling technology is discussed in detail. In the scope of this paper, numerous machining experiments were conducted in unidirectional CFRPs: herein the impact of the type of cutting tool and of process parameters on the quality of machined holes are analysed and discussed (diameter of holes, circularity error and characteristics of uncut fibres). During these investigations, experimental data were evaluated with the help of digital image processing (DIP) and with the help of analysis of variance (ANOVA) techniques. Experimental results show that the amount of uncut fibres can significantly be minimized through the application of wobble milling technology.

Highlights

  • Specific mechanical properties of carbon fibre-reinforced polymer (CFRP) laminates are excellent [1, 2]: these composite materials are widely used in high-tech industries like the automobile and aerospace industries [3]

  • Thousands of high-quality holes have to be machined in order to assemble CFRP parts [6, 7]

  • A unidirectional carbon fibre-reinforced polymer (UD-CFRP) composite material was applied for the machining experiments, where the matrix material was vinyl ester

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Summary

Introduction

Specific mechanical properties of carbon fibre-reinforced polymer (CFRP) laminates are excellent [1, 2]: these composite materials are widely used in high-tech industries like the automobile and aerospace industries [3]. CFRP composites are difficult-to-cut materials due to their (i) anisotropic and (ii) inhomogeneous features, and because of (iii) the abrasive wear effects of their carbon fibres on the cutting tool [8,9,10,11,12]. In this case, carbon-chip treatment is problematic [13] as the chips have to be removed from the machining zone due to (i) health issues and (ii) the wear effect of the carbon fibres on the different parts of the machine tool

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