Delamination-free drilling of thick composite materials

The machining of composite materials is a growing problem in the aeronautical field. In particular, the drilling of these materials, required to assemble different parts, is difficult to control and often leads to delamination at the exit of the laminates. This can affect the strength of the structure. In this paper, the drilling of thick composite plates with a large-diameter drill is studied. An analytical model is developed to determine the critical thrust force at delamination at the hole exit. This analytical model is divided into several zones, along the geometry of the tool active part. A cutting force model, based on the same zones decomposition as the analytical model, is also presented. This model gives the drilling thrust force as a function of the cutting conditions. Finally, the two considered models are used to determine the optimal cutting conditions for delamination-free drilling. The results are validated numerically and experimentally.