Analysis of drilling performance of carbon fiber reinforced polymer with special tool geometries and Raman spectrums

Carbon fiber reinforced polymer (CFRP) composite is an advanced material used in different industrial domains due to its improved strength-to-weight ratio and high flexural strength. Drilling operations are one of the most inevitable manufacturing processes for fabricating CFRP components. However, drilling CFRP composites often induces critical damage in the vicinity of the drilled holes owing to its anisotropic nature, high brittleness, and other physical properties. Hence, a thorough understanding of material removal mechanisms and selection of proper drill tools with optimized tool geometry is indeed a prior necessity to drill high-quality holes with minimal defects in CFRP composites.

In this work, an attempt is made to investigate the influence of drill tool point angle on the drilling mechanism and drilled hole quality in CFRP composites. Drills with different point angles such as 90°, 118° and 135° are examined under various drilling settings. Thrust force is employed to analyse the dynamics of the drilling process and material removal mechanism. Residual stresses induced during the drilling operation are examined in detail using micro-Raman spectroscopy analysis. Experimental results show that reducing the point angle to 90° significantly improved drilling performance in CFRP composites compared to the standard 118° drill. At higher feed rates (0.06–0.16 mm/rev), the PA90 tool caused 11.5 % and 17 % less damage than the PA118 and PA135 tools, respectively. The 90° tool also produced fewer residual stresses, as indicated by Raman band shifts. Thus, the 90° point angle tool is suitable for high-speed machining. The point angle is a critical parameter and its impact on damage induction and the quality of the drilled CFRP is demonstrated in detail.