Investigation of milling nomex (honeycomb) composite material

Composite materials are created by combining two or more materials with different structural properties. These materials typically consist of a matrix and reinforcing fibers or fillers. The properties of composites vary depending on the choice and arrangement of the components used. Nomex, produced in a honeycomb geometry, is widely preferred in sectors such as aerospace, aviation, marine, and automotive due to its high strength, light weight, and flame resistance. The core structure can be manufactured in various geometries and sizes, such as square prism or hexagonal prism, but their anisotropic nature makes machining processes quite complex. These types of composites are usually assembled using fasteners like rivets and bolts. CNC milling is performed to create slots for fasteners or to achieve a desired surface. In this research, the cutting forces and delaminations that occur during the CNC milling process were examined. The aim of this study is to determine the most suitable cutting tool geometry, spindle speed, and feed rate. The experiments used glass fiber prepreg-coated Nomex honeycomb sandwich material and were conducted with helical three-flute (RRFE060) and two-flute chip breaker type (RCFE060) cutting tools. The processes were carried out using different feed rates (150, 300, 450, 600, 750 mm/min) and spindle speeds (2500, 7500 rpm) with the slotting method. Cutting forces were measured using a dynamometer, and delamination results were evaluated based on images of the cut slots. Generally, it was observed that at a spindle speed of 7500 rpm, the cutting forces and the number of uncut fibers significantly decreased. Additionally, as the feed rate increased, delaminations became more frequent, and cutting forces increased. The cutting forces were higher with the RRFE060 cutting tool compared to the RCFE060 tool.