Impact of the abrasive water jet milling process on the damage and surface characteristics of CFRP composite

Milling by Abrasive Water Jet (AWJ) is a novel process introduced recently, which can potentially be used for repairing composite structures. It is a promising technique when compared to conventional machining which has inherit problems like extensive damage and dust generation. Till now material integrity of the composite structures machined by AWJ process are not well investigated. In the present work, influence of AWJ milling parameters on the surface characteristics and size of damage (craters) are investigated for carbon/epoxy composite specimens using full experimental design. The surface quality was characterized by 2D Profilometry, 3D optical topography and Scanning Electron Microscopy (SEM) observation. In addition, surface topologies were analyzed to obtain roughness parameters and crater volume, which were correlated with machining parameters. SEM images reveal the presence of damages (in the form of craters, ridges, broken fibers and embedded abrasive particles in matrix) whose size is strongly influenced by the machining parameters. It is seen that the average crater volume increases by 350% when pressure varies from 80 MPa to 140MPa. ANOVA technique indicates that surface roughness and crater volume are highly influenced by jet pressure and formation of ridges is influenced by scan step compared to other parameters.