An analytical model for predicting critical feed rate in drilling of composite laminates

The thrust force during drilling is one of key indexes to describe machinability of composite laminates owing to the fact that it directly affects the quality of drilled holes, especially drilling-induced delamination. The size of drilling-induced delamination zone has been shown to be related to the thrust force during drilling composite laminate, and it is believed that there is a critical thrust force below which no delamination appears. However, thrust force strongly depends on drilling parameters and it is not possible to control it directly. Thrust force can be correlated with feed rate. This paper presents an analytical model for predicting critical feed rate at the onset of delamination propagation. The model proposed is based on linear elastic fracture mechanics, classical plate bending theory and the mechanics of oblique cutting.