Machining of Kevlar Aramid Fiber-Reinforced Plastics (K-1226) Using Solid Carbide Step Drill K44

Abstract

Composite materials have found increasingly wider application in aircraft, space vehicles, offshore structures, piping, electronics, automobiles, boats, and sporting goods due to their superior properties and high strength to weight ratio. Among these, the aerospace industry is using composite materials for numerous components and structures. Many of these components require machining during its fabrication. Machining of composite materials is difficult to carry out due to the damage being introduced into the component in the form of delamination, fiber pullout, and local cracks. Further, rapid wear development in the cutting tool also takes place during the machining of composite materials. Conventional machining processes such as turning, drilling, or milling can be applied to composite materials, provided proper tool design and operating conditions are adopted. Kevlar Aramid Fiber-Reinforced Plastics (K-1226) is widely used in the industry due to its chemical stability at high temperature and resistance to wear. Studies show that conventional cutting of this laminates is extremely difficult due to the frictional force developed via thermal expansion of substrate material. This has restricted the Kevlar component usage. In this regard, the present paper describes the effective method for drilling K-1226 material with reduced machining defects and tool wear using solid carbide step drill K-44. The drilling operation is carried out on K-1226 composite laminates of thicknesses 8, 10, and 12 mm. K 44 step drill with varying cutting speed and feed rate are used for drilling holes. The drilled laminates are examined using C-Scan analysis. The results show dramatic improvements of the tool performance and surface quality. K44 is a single shot drill, designed to replace three conventional drills having diameters 6.5, 8.5, and 11.5 mm. The tool geometry detail of K44 drill is also presented in the paper.