Influence of fibre proportion and position on the machinability of GFRP composites- An FEA model

More commonly considered criteria for judging the machinibility are the cutting forces on the tool and power consumption. A classical Merchant’s model is widely used to predict the cutting forces while machining isotropic material. However, no such model exists to predict the cutting forces while machining orthotropic materials. In this paper, an effort is made to modify the Merchant’s formula by incorporating the K-factor to evaluate the shear strength, the fibre orientation as shear angle and a constant coefficient of friction. The cutting forces evaluated by modified Merchant’s model on unidirectional GFRP composite material has been compared with the results predicted by two-dimensional FEA model. In FEA model both maximum stress and Tsai-Hill failure criteria were used to simulate the chip separation. The influence of composite design, in particular the fibre proportion and orientation on cutting forces has been investigated. The higher fibre proportion in the composite caused an increase in cutting force values. Fibre orientations 45° and 60° have shown favorable results. The FEA predicted results have shown good agreement with the results evaluated by modified Merchant’s model.