Investigation on the performance of SiAlON ceramic drills on aerospace grade CFRP composites

• Novel SiAlON drills were manufactured and tested on drilling of CFRP composites.
• The geometry of the primary cutting edge affects the thrust force and torque.
• The thrust force increased by ∼80% after drilling of three holes due to wear.
• Push-out delamination was observed as independent from the cutting parameters.
• Decrease in point angle resulted in a decrease in forces and peel-up delamination.

Carbon fiber reinforced polymer (CFRP) composites are widely used in aircraft structure due to their outstanding physical and mechanical properties. Drilling is one of the most critical operation in the handling of CFRP composites, since the delamination free holes with high dimensional accuracy are required for assembly. The quality of the machined holes strongly depends on machining conditions, tool geometry and tool wear. There are a limited number of tool materials which can survive in the abrasive cutting conditions formed by the fractured carbon fibers during drilling. SiAlONs are promising materials for the machining of CFRP composites due to their superior abrasive wear resistance. SiAlON ceramics have been reported for the first time in the literature as cutting tool materials for drilling of CFRP composites in this study, where α/β-SiAlON drilling tools with four different sets of common drill geometries were manufactured and tested extensively on drilling of aerospace grade CFRP composites. The effects of cutting parameters and geometrical features of novel α/β-SiAlON drilling tools on the cutting forces and the peel-up delamination of the machined holes were investigated. It was observed that the point angle and chisel edge length of the novel SiAlON drilling tools are the main parameters that affect the maximum thrust force and delamination during drilling. The thrust force exhibited an increase during drilling tests, indicating that an abrasive wear occurs at the cutting edges of the SiAlON drilling tools.