Influence of cutting speed and tool geometry on form and machine tapping of carbon fibre-reinforced composites

Abstract

Fibre-reinforced composites are widely applied in structural parts due to their high specific mechanical properties. The use of self-tapping screws in aerospace applications has been considered a controversial joining technique for years, owing to the risk of distortion and cracking of the composite material during fastening. The typical mechanical component used to assembly aeronautic parts is the rivet. Thus, the study of alternative components to produce joints and both their application and performance is necessary. This work investigates the threading processes by the forming and machining in carbon fibre-reinforced composites. Three taps were used in this work, the first one based on form tapping and the other two related to machine tapping. The results indicated that in the two tapping processes, the mechanisms involved consisted of a combination of plastic deformation, shearing, and bending failure. In general, the speed of 28 m/min provides minimum thrust force, 166.5% lower than the 10 m/min speed, in machining process, while the temperature is reduced by 53.9%. The speed/tool of 28 m/min and MH-tap (tapping process) reveals the most efficiently interaction. Filling rates of the thread profiles were acceptable for practical engineering applications, mainly when high speeds were applied. The results demonstrated that threaded workpieces could be applied to aeronautics components with limitations; nevertheless, additional studies should be carried out to determine the application range.