Modeling of delamination during milling of unidirectional CFRP

Abstract

The production of CFRP needs edge trimming in order to remove burrs as well as undefined orientated fibres and to shape the final part contour. Edge trimming is usually done by contour milling. The quality of machined edges may be affected by fibre protrusions and delaminated fibres which cause manual repair or may even lead to scrap. Delamination of fibres is often initiated by stresses applied during engagement of the cutting edge. Based on measured cutting forces, the stress distribution and the inter fibre fracture modes in the boundary zone of the machined surface are calculated using Lekhnitskii's theory of elasticity for anisotropic elastic bodies and the fracture criteria of Puck. In course of the continuing edge trimming process, fibre ends in the damaged boundary zone might not be cut off but deflected by subsequent tool engagements, as can be observed in high speed videos. In the case of existing fibre protrusions, a relation between the minimum depth of the damaged zone, the fibre orientation at the machined edge and the fibre properties was derived using elementary bending models. The analysis underlines the existence of only one type of surface ply delamination i.e. fibre protrusions and fibre delamination always occur together. Copyright © 2013 Elsevier B.V.