Fiber-reinforced plastic is one of the top priorities lightweight materials with excellent mechanical properties for the aerospace industries in recent years. However, it is difficult to machine despite having unique properties due to its non-homogeneous and abrasive nature in alternate fiber and matrix layers. Thus, it is found to be a challenging task to drill hole on such hard-to-machine materials, which is highly essential for the development of most of the engineering structural components. The present work addresses various drilling-induced defects such as delamination, circularity error, and roughness variations in the hole surface during drilling of quasi-isotropic cross-fiber oriented bi-directional woven-type carbon fiber reinforced plastic laminate using a full factorial design of experiments for different drill geometry. The response surface methodology was considered for the regression model development, which was found to be highly significant. The machining forces with associated torque have also been acquired during drilling, which was divided and further analyzed in time domain to correlate with drilling flaws. The drilling-induced delamination was found to be higher at a high feed rate using a higher drill point angle due to substantial thrust force generation at the initial stages in the drilling cycle. However, the internal surface finish with associated circularity error was reduced for higher spindle speed with less feed rate using a low drill point angle because of low torque fluctuation at the final drilling phases. The axial thrust force was found to be a prime indicator of drilled hole surface delamination, whereas drilling torque precisely indicated internal surface roughness as well as circularity error. The global root mean square, along with a local peak of thrust and torque, both were highly essential to completely characterize the drilled hole quality.
Drilling of fibrous composites like carbon fiber reinforced plastics (CFRPs) is always considered a grim job to perform owing to its abrasiveness and inhomogeneous properties. Compared to the available studies, the present work addresses the parametric investigation on drilling capability of TiAlN- and TiN-coated drills over the uncoated one. The delamination factor, surface roughness, and circularity error in CFRP were considered as the quality features. The acquired thrust and torque were analyzed in the time domain as well as the time–frequency wavelet field, followed by a sensitivity analysis between decomposed original force–torque signals in different phases. Finally, an attempt was made to improve the predictability of drilled hole quality using decomposed wavelets of force and torque extended to hybrid force–torque wavelets of the best features to the developed regression models. The feed rate was more predominant than spindle speed on delamination evidenced by higher axial thrust particularly using coated tools. However, the coated drills generated more uniform torque than the uncoated drills and improved the drilled hole quality as well. The torque wavelet was a better indicator of hole surface integrity than force wavelets in which intermediate frequency band torque and low-/high-frequency band force wavelets were found to be more significant.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.