Mechanistic modeling of cutting forces in milling of unidirectional Glass Fiber Reinforced Polymer (UD-GFRP)

Abstract

Mechanistic models, established on experimental data, are recognized for their precision and simplicity in implementation. In this context of milling, the modeling of cutting forces, specifically radial and tangential components, has been extensively explored for unidirectional carbon fiber-reinforced polymer (UD-CFRP) parts. These models account for the anisotropic nature of fiber-reinforced polymers (FRPs), with cutting coefficients that vary based on the instantaneous cutting angle. However, due to the inherent flexibility of these materials, primarily attributed to their low thickness, axial cutting forces must also be incorporated to accurately represent the phenomena occurring during the machining process. This study develops a model for calculating cutting forces in three spatial directions for UD-GFRPs (unidirectional Glass Fiber-reinforced polymers). Building on an existing model from the literature for UD-CFRP, this new version introduces several modifications. First, the model validated for CFRPs must be extended to GFRPs. Secondly, the model must be extended from two dimensions to three dimensions. Finally, to ensure that the model includes only the actual contributions of the trimming operation, machining tests will be performed using only the rolling teeth. The cutting coefficients are modelled as a periodic function with a fundamental period of π. A first-order Fourier series was chosen for this purpose. Fourier series parameters are identified from the milling forces measured during a set of slotting operations at three feed rates and four fiber orientations. While the average levels of cutting forces are accurately modelled for both slotting and shoulder milling (with 50% immersion in up milling), the modeling of force amplitudes still requires improvement.