Surface quality and kerf width prediction in abrasive water jet machining of metal-composite stacks

Machinability of stacked Titanium (Ti6Al4V) and CFRP was evaluated using Abrasive Water Jet (AWJ) machining process. The experimental study was conducted using three pressure levels - 200, 275 and 350 MPa. Traverse speed was varied between 1 and 10 mm/s for two stacking configurations (Ti/CFRP, and CFRP/Ti). The erosion characteristics, kerf width and surface roughness was studied as a function of process parameters. Surface roughness and kerf width variation was high at low jet power conditions, as described by lumped parameters ((E) over dot/u and (E) over dot/hu). The minimum average roughness R-a for Ti and CFRP was less than 3.5 mu m and 4.5 mu m respectively for both the stacking sequence. The kerf width increased significantly, especially when Ti6Al4V is at top in which case low-energy, turbulent jet diverges at the exit from Ti6Al4V. Mathematical regression models were developed to predict kerf width. An energy based, semi-analytical model was proposed to predict the kerf geometry with R-2 = 92.26%.