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

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.

Automated summary

This paper investigates the formation mechanism of delamination in entrainment abrasive waterjet machines and finds that the delamination phenomenon is mainly caused by the material's response to shock pressure and shear stress. Furthermore, the study also reveals that the delamination is influenced by water pressure and the delamination area varies among different composite materials.