Analysis of the surface quality of CFRP/Al/CFRP composites after abrasive waterjet cutting

Hybrid layered structures made of carbon fibre-reinforced polymers (CFRPs) and metals exhibit very good mechanical properties. For this reason, they are more and more widely used in different industry sectors, e.g. aircraft, automotive, and defence. High quality requirements imposed by these sectors require the development of a machining technology suited to structures of this type. Due to different properties of individual layers, the abrasive waterjet cutting (AWJC) of hybrid materials is more complex than that of mono materials. The objective of this study was to examine the quality and accuracy of CFRP/Al/CFRP layered structures after abrasive waterjet cutting. The study focused on the evaluation of jet lag, surface roughness, and surface morphology. Geometrical accuracy was evaluated based on surface perpendicularity and top edge radius. The study analysed the impact of cutting parameters – feed rate and abrasive flow rate. Given the difference in process characteristics, two variants of AWJC were analysed – perpendicular and parallel relative to the carbon fibre direction. Obtained results demonstrated that machining effects strongly depended on the applied cutting conditions, particularly feed rate. For most cases, the use of higher feed rates caused surface deterioration, which was primarily reflected by jet lag and considerable surface roughness. The use of a low abrasive flow rate also had a negative impact on surface quality, in addition, the jet progressively loses kinetic energy as the cutting process advances through successive material layers. Similar relationships were also observed in terms of geometrical accuracy.