# A Novel Finite Element Method Approach in the Modelling of Edge Trimming of CFRP Laminates
Drilling modelling investigations mostly assess the impact that machining factors have on the surface delamination of the outer plies [26; 28]. [PERSON] et al. [29] found that the selection of high cutting speeds and low feed rates reduce the delamination levels, torque, and thrust force considerably. Later, [PERSON] et al. [30] developed a simplified drilling FE model, which drastically reduced the computational time required for a complex drilling model in a simulation without a significant decrease in the accuracy of the predictions. The morphology of the drill bit plays a relevant role in reducing the machining-induced damage in drilling operations. For instance, [PERSON] et al. [31] concluded that the use of high stage ratios in step drill bits is essential to decrease the push-out delamination. The development of more sophisticated FE models in this field have successfully studied the drilling process in more complicate composite types, such as woven or biocomposites [32; 33]. In general, the FE modelling of metal milling operations has been developed in numerous investigations in recent years. However, these models still offer important limitations. For instance, the development of advanced machining friction models is required to improve the quality of feed force predictions [34]. The Johnson-Cook model is the most used to define the plastic behaviour of these metals with linear or exponential progressive damage models [35]. Many advances in this field have been achieved with these investigations. For example, [PERSON] et al. [36] found that the cut-off transition between the burnishing regime and the chip formation regime is in a feed per tool range of 1-1.4 microns. Finally, [PERSON] et al. [37] showed that the use of advanced modelling techniques such as the Coupled Eulerian-Lagrangian approach significantly improves the predictions quality in terms of chip shape and machining forces. Although composite milling is one of the most common operations to achieve high-quality surface finishing in the industry, they have not been widely modelled so far. To study these operations, simplified FE orthogonal cutting models are implemented because of the high difficulty of simulating explicitly the characteristic material failure and chip separation of the milling process [38]. Therefore, the development of sophisticated FE models capable of solving the doubts about the physical mechanism of failure concerning composite milling is necessary for future investigations. Furthermore, the implementation of damage algorithms to mimic the characteristic progressive loss of mechanical properties and crack propagation observed in the damaged areas is vital to accomplish this matter [39]. The orientation of the cracks plays a fundamental role in the appearance of defects in the mechanical surface, such as surface roughness or sub-surface damage. A clear increase in these variables is observed in fibre orientations greater than 90\({}^{\circ}\) due to the fact that the great bending effect causes the fibre breakage to occur in a very irregular way below the cutting surface as well as a significant increase in the fibre matrix debonding extension into the sub-surface damage [40; 41]. However, the orientation of the fibres is not the only factor that influences the increase in sub-surface damage; the wear of the tool tip also contributes significantly to the increase in the length of the cracks propagating into the machined surface. The impact of blunt tool tips (large tool edge radius) interacting with the fibre tends to push the fibres, generating a significant bending effect rather than shearing them. This mechanism increases the size of the cracks produced by the fibre-matrix debonding below the machined surface, considerably reducing the structural integrity of the part [42]. Therefore, this tool wear must be quickly detected by evaluating variations in the mechanical responses.