Drilling characteristics of carbon/epoxy and carbon/polyimide composites

Carbon/epoxy and carbon/polyimide composites are, respectively, high-performance thermoset and thermoplastic polymer matrix composites being widely utilized in the modern industrial fields due to their superior mechanical/physical properties. However, there is no study available in the literature to differentiate the machining behaviors between these two types of composites. The present paper contributes to the scientific understanding of the drilling characteristics of the two different carbon fiber reinforced polymers (CFRPs). The novelty of the current investigation lies in revealing the fundamental machining behavior of the carbon/epoxy and carbon/polyimide composites and in distinguishing their drilling responses. A comparative drilling study was carried out using the TiAlN-coated twist drills with an emphasis on the analysis of the mechanical/thermal effects of the chip removal process governing the drilling of the thermoset and thermoplastic laminates. Aspects including the drilling forces, machining temperatures, hole diameters, and cylindricity errors were quantified. The results indicate that the machining behaviors of the CFRPs are greatly affected by the presence of the matrix material. The carbon/epoxy composites produce higher drilling forces, higher cutting temperatures, and poorer hole geometrical accuracy than the carbon/polyimide ones, which indicates a much poorer machinability of the thermoset composite. The phenomenon is attributed to the different cutting behaviors of the thermoset and thermoplastic matrices impregnated within the CFRPs.