Direct monitoring of hole damage in carbon fibre-reinforced polymer (CFRP) composites

Carbon fibre-reinforced polymer (CFRP) composite laminates have good specific material properties, these composites are therefore widely used by the high tech industries. Machining operations are often necessary in order to achieve dimensional requirements. However, CFRP is a difficult-to-cut material due to its non-homogenous and anisotropic features and the strong wear-effect of carbon fibres on the cutting tool. Increasing hole numbers causes the increase of cutting edge radius of the cutting tool, therefore hole damages (uncut fibres, delamination etc.) occur more often. The main objective of the present paper is to minimize uncut fibres in CFRP using direct monitoring of hole damage. Firstly, numerous orbital drilling experiments were conducted and the characteristics of uncut fibres were analysed. Secondly, the orbital drilling experiments were repeated with direct monitoring of uncut fibres and process control was applied in order to decrease the size of the burr area. Results show that hole damage decreased with the application of the used process control.