Research study of factors affecting difference between hole diameters in hybrid metal-composite drilling

Abstract

The assembly of airframe sections often requires the joining of parts made of composite materials to the metallic inner structure using bolts, rivets, and tight-diameter-tolerance drilled holes. Whilst the problems that arise in the drilling of composite-and-metal hybrid stacks are well known in industry little academic work has been done to solve these issues. This paper focuses on the problem of minimizing the difference in the diameters of the hole in each material in a hybrid stack. A statistical analysis is performed on an extensive historical data set collected in an industrial setting and a 2³ factorial experimental design is also performed Among the studied factors affecting the extent of this difference (nominal diameter, type of drilling machine, nature of materials, feed rate, and spindle speed), only the nominal diameter does not show a significant influence on the value of the difference in the diameters. The type of drilling machine, the nature of the materials that make up the stack, and the feed rate all have a strong influence on the difference in diameter but cutting speed displays a smaller influence than these factors.