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Drilling Conditions on Hole Quality for CFRP Laminates



Introducing circular holes in carbon fibre-reinforced polymer (CFRP) laminates by drilling is a typical process involved in making composite airframes. It is a complex process owing to materials heterogeneity, configuration, sharpness and feeding rates of drills, and to the fact that reinforcements and debris are very abrasive. CFRP laminates are prone to drilling-induced damage that comprises delamination and edge chipping. Drills of different configurations have been developed for practical usage, though current studies on drilling performance and integrity were mostly focused on twist drills. Examination of processing parameters on drilling quality and integrity is critical for assessment of integrity of holes and the tool life. In this study, drilling performance and integrity of circular holes in CFRP laminates for making the flat panel of a commercial aircraft were investigated using drills of three different configurations, Dagger drill, drill Reamer and twist carbide drills by employing drilling speeds of 500, 1000 and 2000 rpm and different back support. Several output responses such as thrust force and torque are measured. Quantification of quality and integrity of holes is conducted by evaluating surface roughness, heat distribution, roundness, chip size, and damage factor defining delamination at hole edge, which provide some guidelines for optimisation of machining parameters for introducing circular holes in practical operation.

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