Numerical analysis of the influence of tool wear and special cutting geometry when drilling woven CFRPs

Abstract

CFRPs drilling is a common process in the aerospace industry carried out prior to components assembly. Machining induced damage leads to significant percentage of component rejection. Damage extension strongly depends on drilling geometry and cutting parameters. Fresh drill geometry changes with cutting time due to the wear progression and the risk for hole quality is enhanced as cutting progresses. The influence of wear on hole quality has been analyzed in the literature using mainly an experimental approach.

Simulation of drilling process is an effective method that can be used to optimize drill geometry and process parameters in order to control hole quality and analyze the drill wear evolution. In this paper a finite element model for drilling woven CFRPs, reproducing both fresh and worn tools, is presented. Two different point angles considering fresh and honned edge were modeled. A progressive intra-laminar failure model based on the Chang and Chang model is considered. Cohesive elements allowed the analysis of inter-laminar damage (delamination). The model demonstrated its ability to predict thrust force and delamination for different values of feed rate and cutting speed. Model predictions show the influence of tool geometry (including variations induced due to wear) on delamination.