Keywords: abrasive waterjet machining, polymeric composites, finite element modelling.

The main objective of this work is developing a model for the prediction of the depth of cut of inhomogeneous materials (polymeric composites reinforced by fibers). A nonlinear dynamic finite element model has been developed in order to explain the behavior of the process. The main task of such model is to define an interaction between the tool and a workpiece. Two analyses has been conducted: the first, the impact of a single abrasive particle into the surface of the workpiece and the second, the impact of a pure waterjet in order to observe the penetration of water inside material and tracing failure phenomena such as delamination. Additionally deformations and stresses in the workpiece material, the vicinity of the cutting interface as a result of the erosion impact by abrasive waterjet were obtained.

In this work the following tasks were performed: stresses and deformation analysis in the local immediate contact surface with a high-pressure waterjet using the finite element method and the experimental research conducted for evaluation of the influence of the main parameters of the process on the quality of the cutting surface of the kerf.

Evaluation of strongly non-linear phenomena (i.e. deformation until cracking of material at a very high velocity) of the damage using the finite element method requires specific evaluation procedures. The choice of process for stresses and displacement distributions is very important while the preparation of dynamic investigations and solution method. In most critical cases general accessible evaluation procedures cannot be used during the dynamic analysis.

The failure criterion model was prepared as separate external user subroutine. During the deformation of orthotropic material, the MSC Dytran system in each time step turns to return to the external user subroutine. According to that subroutine a workpiece will be deformed and eroded.

The analytical procedures used here for modeling delamination rely on the straightforward-stacked sublaminate approach whereby a laminate is modeled as two or more sublaminates held together with spring elements. The spring elements effectively model an interlaminar region and failure of spring elements in the model represents crack growth. Failure models based on fracture mechanics were used to build models that accurately capture the dynamic delamination response of composites. These procedures were implemented using MSC-Dytran.

The depth prognosis of the kerf permits to the specification of values below the FEA relative error of 10% in specified range of AWJ pressures.

The FEA analysis of pure waterjet penetration shows a significant probability of exhibiting delamination phenomena. Lack of abrasive particles in waterjet cutting contributes to choice of the easier penetration of the waterjet (i.e. space bonding interlaminar) where lower strength of material exists.

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