Micro-mechanical modeling of machining of FRP composites – Cutting force analysis

Orthogonal machining of unidirectional carbon fiber reinforced polymer (UD-CFRP) and glass fiber reinforced polymer (UD-GFRP) composites is simulated using finite element method (FEM). A two-phase micro-mechanical model with fiber assumed elastic and the matrix elasto-plastic is used to estimate the cutting forces during machining. A cohesive zone simulated the interface debonding between the fiber and matrix. Fiber failure was based on maximum principal stresses reaching the tensile strength. The matrix elastic modulus was degraded to include damage once yield strength was reached. The model assumes plane strain and quasi-static condition. The cutting forces during orthogonal machining were studied both experimentally and numerically for a range of fiber orientations (θ), depths of cut (t) and tool rake angles (γ). The contact forces developed between the tool and the fiber provided a good estimate of the cutting (Fh) and thrust (Fv) forces during the orthogonal cutting process. The failure of fiber is found to be a combination of crushing and bending, with the bending effect becoming more significant as the fiber orientation changes from 90° to 15°.