Delamination of Graphite/Epoxy Laminate During Drilling Operation

Delamination due to drilling is one of the major concerns in machining a composite laminate. This paper employed NIKE2D finite element code to predict the critical load for delamination in drilling simulation. Good agreement is achieved with the approximation analytical solution and the finite element results for the case of the model using isotropic material property. A circular plate of quasi-isotropic graphite/epoxy laminate with and without an aluminum plate backing was investigated for drilling load-induced delamination. It is found that drilling force-caused delamination can be significantly increased as the uncut portion is beyond a quarter thickness of the entire laminate thickness with an aluminum backing plate. It is suggested that the drilling operation be controlled as the drill nears the exit plane.