The effects of stacking sequence on drilling machinability of filament wound hybrid composite pipes: Part-1 mechanical characterization and drilling tests

In the first part of this two-part comprehensive study, mechanical properties and machinability characteristic of filament wound hybrid composite pipes with various stacking sequences of glass and carbon fibers (Glass-Carbon-Glass (GCG), Carbon-Glass-Glass (CGG), and Glass-Glass-Carbon (GGC)) were investigated experimentally. In order to determine the mechanical properties of the pipes, hardness test (Shore D), ring tensile test (ASTM D2290), and burst test (ASTM D1599) were carried out. Machinability tests were performed at various feed rates (50, 150, 250 and 350 nun/min) and spindle speeds (796, 1592, 2388 and 3184 rpm) using with and without a back-up. The results showed that stacking of the carbon layer between two glass layers (GCG) presented better performance in terms of mechanical properties and machinability characteristic. The maximum ring tensile stress of GCG specimen is 27% and 19% higher than those of GGC and CGG specimens, respectively. On the other hand, the lowest thrust forces measured during the drilling of GCG specimen while the GGC represented highest values. In addition, the use of back-up led to an increase in thrust force. The highest increase was observed in GGC sample. In GGC sample, a change in a spindle speed increased thrust force by 18-35%, while a change in feed rate increased thrust force by 20-30%.