Abrasive waterjet machining of polymer matrix composites - Cutting performance, erosive process and predictive models

An investigation of the cutting performance and erosive process in abrasive waterjet (AWJ) machining of polymer matrix composites is presented. It shows that AWJ cutting can produce good quality kerf at high production rates if the cutting parameters are properly selected. Plausible trends of the cutting performance are discussed, as assessed by the various kerf geometry and quality measures, with respect to process parameters. The traverse speed, water pressure and abrasive flow-rate are found to have a profound effect on the total depth of cut to kerf taper angle, while the first two variables also have a large on the kerf width. The study shows that the optimum jet forward impact angle in the cutting plane is about 80 degrees which increases the total depth of cut only marginally, and has little effect on the other kerf characteristics. It is found that good quality kerf without delamination can be achieved if through cut is attained. A scanning electron microscopy (SEM) analysis of the cut surfaces reveals that the erosive process for the matrix material (resin) involves shearing and ploughing as well as intergranular cracking. Shearing or cutting is found to be the dominant process for cutting the fibres in the upper cutting region, but the fibres are mostly pulled out in the lower region. Mathematical models for the total depth of cut are finally developed and verified, together with empirical models for the other kerf geometrical features.