Mechanistic cutting force modelling for micro-drilling of CFRP composite laminates

This article presents a mechanistic model to predict thrust force and torque in micro-drilling of carbon fibre-reinforced plastic (CFRP) composite laminates. Tool edge radius effects are considered in this model to predict cutting forces even at low feed values which are comparable to the tool edge radius. As greater fluctuation of cutting force is very common in micro scale machining of composite material due to its layered structure, fabric plies and epoxy resin matrix layers are considered in this model as separate phases rather than as equivalent homogeneous material. Separate sets of cutting coefficients for each phase are determined from the experimental results. The fluctuations of average thrust and torque in alternate layers of fabric plies and epoxy resin matrix are predicted and validated with new experimental results of micro-drilling with a 0.5 mm diameter tungsten carbide tool. In both layers, the model predictions are close to the experimental results. Though the prediction errors in epoxy resin matrix are comparatively higher than the errors in fabric plies, these are reasonable considering the complex sub surface damage mechanism due to epoxy resin matrix failure and interfacial debonding.