Investigation of delamination and surface quality of machined holes in drilling of multiwalled carbon nanotube doped epoxy/carbon fiber reinforced polymer nanocomposite

Abstract

In the drilling of carbon fiber reinforced polymer composite materials, drilling-induced delamination and surface roughness of machined holes are causes of major concern, particularly, when components, made of carbon fiber reinforced polymer, are used in the aerospace industry. In order to minimize these drawbacks, an innovative technique has been developed by adding multiwalled carbon nanotube in the polymer matrix to improve interlaminar shear strength and flexural strength of the laminates. Experimental results indicate that with this process, flexural strength and interlaminar shear strength get enhanced by almost 24% and 28%, respectively, when compared to neat epoxy carbon fiber reinforced polymer composite. The image process results reveal that delamination factor gets decreased by 21% and 28.60% at the entrance and the exit side, respectively. This, in turn, not only reduces the delamination factor during the process but also facilitates the process to be carried out more smoothly. During this investigation, scanning acoustic microscope was used to study ply-by-ply damage followed by ultrasonic C-scan on both sides of the laminates, which showed good agreement with the experimental results. Measurement of surface roughness of the machined hole showed the maximum R_a value of 5.03 µm in neat epoxy carbon fiber reinforced polymer composite. However, a sample with 1.5 wt% of multiwalled carbon nanotube showed a decline in R_a value (1.18 µm). Thus, addition of multiwalled carbon nanotube to the polymer matrix could reduce the drilling-induced delamination as well as the surface roughness of machined hole simultaneously.