Modelling of delamination due to hydraulic shock when piercing anisotropic carbon-fiber laminates using an abrasive waterjet

Abrasive waterjet (AWJ) piercing of composite laminates typically generates interlaminar delamination due to the hydraulic shock ('water hammer') associated with liquid jet impact. This paper extends previous liquid jet impact literature by examining the effects of hydraulic shock on an anisotropic carbon-fiber/epoxy laminate using finite element analysis and experiments. A transient fluid-structure interaction model was developed to simulate the AWJ impact process, thereby providing a detailed explanation of the underlying mechanisms leading to substrate damage in an anisotropic material. The fluid domain of the numerical model examined the effects of varying pressure and nozzle size on the magnitude of the hydraulic shock. The forces generated in the fluid domain acted as the loads in the transient model which utilized cohesive zone modelling to predict the initiation of delamination cracks in the carbon-fiber/epoxy substrate. The numerical results showed that increased pressure and nozzle size resulted in increased hydraulic shock loading, and increased ply debonding. These results were verified experimentally on AWJ pierced specimens using 3D x-ray micro-tomography. The numerical and experimental results showed that the composite anisotropy produced an asymmetric shock loading along the liquid-solid interface, which contributed to the asymmetric delamination in the upper ply of the composite.