Characterization and modelling of milling induced damage in the carbon fibre reinforced composite laminates

This manuscript introduces an energy-based formulation for a three-dimensional ply failure model to investigate the milling-induced damage of UD carbon fibre laminate, using a VUMAT subroutine. The model incorporates a novel fibre-kink formulation, where kink-band initiation is characterized by matrix failure criteria within the localized deformation band . The modelling approach integrates continuum damage mechanics (CDM) with cohesive interface elements to predict both intra-translaminar and interlaminar failure modes. At the ply level, the CDM model takes in account in-plane shear failure, fibre failure (in tension/compression), and matrix cracking (in tension/compression). Machining-induced delamination is evaluated using native cohesive interface elements available in ABAQUS FE code. Cutting forces are computed at each increment of time during the simulations and experimentally validated through dry milling tests. A full factorial design (2 3 ) is established to identify the effects of cutting speed, depth of cut and tool geometry on the surface roughness, cutting forces and milling-induced damage on the UD carbon fibres. In general, a fairly good correlation between numerical predictions and experimental data in terms of milling force was found, with 6.51% maximum deviation. The 4-flute end mill generated higher cutting forces (37.9%) compared to the 7-flute tool, leading to increased extent of carbon fibre tearing and matrix fragmentation. The results outline the multi-mechanism nature of CFRP milling damage: at lower depths of cut, the damage is relatively uniform and characteristic of a ductile-dominated regime, whereas increased cutting depths promote brittle failure modes such as fibre pull-out, interfacial debonding, and delamination.