Mechanisms of pop-up delamination in laminated composites pierced by the initial pure waterjet in abrasive waterjet machining

Abstract

The entrainment abrasive waterjet machines start with a pure waterjet before abrasives are injected to avoid nozzle clogging. This pure waterjet impact is the primary cause for delamination in the form of edge pop-up of laminated composites. This paper presents an investigation into the pop-up delamination formation mechanisms. A coupled fluid–solid numerical model is developed by coupling smoothed particle hydrodynamics method and finite element method. It is found that pop-up delamination is initiated due to the material’s elastic response to a rapid release of shock pressure to stagnation pressure and the traverse shear stresses induced by the bending of the plies. A hydro wedging effect between the plies due to flow divergence propagates the delamination. There is a threshold value for the water pressure above which pop-up delamination does not increase significantly. Moreover, the smallest delamination area takes place on the [0]12 composite, followed by the [0/45/90/-45/0/45]s and [0/90]3s composites.