This work investigates the application of ultrasonic-assisted drilling (UAD) to aerospace-grade carbon fibre reinforced plastic (CFRP), with focus on process characterisation, force response, tool wear, and hole quality. A key output is the development of a novel measurement method whereby tool vibration amplitude was quantified using a high-speed camera and bespoke MATLAB software to track a datum feature etched on the drill tip. This enabled direct observation of micron-level displacement at ultrasonic frequencies and was successfully applied both out-of-cut and during drilling.
Quantitative assessment of drilling performance was carried out through force measurement, three-dimensional tool wear analysis, and analysis of drilled holes. Force data showed that ultrasonic assistance produced a consistent reduction in thrust force relative to conventional drilling, with reductions of 5–10% in the early stages of tool life and up to 20–40% at steady state. These reductions were observed across 300 holes per condition, demonstrating sustained process benefit. Tool wear analysis revealed that while ultrasonic excitation introduced a more aggressive wear mechanism initially, overall wear behaviour was comparable to conventional drilling after extended cutting. The onset of coating failure was shown to strongly influence instantaneous force response.
Hole quality assessment demonstrated that ultrasonic assistance can deliver improvements in dimensional accuracy. All ultrasonic frequencies maintained hole diameters within tolerance, with improved stability in circularity and cylindricity compared to conventional drilling. Uncut fibres were observed at hole exit in isolated cases, though these did not prevent compliance with aerospace drilling standards.
Collectively, the work establishes that ultrasonic assistance offers tangible benefits in CFRP drilling, including up to 40% reduction in thrust force, improved dimensional consistency, and a potential route to extended tool life. The novel amplitude measurement technique provides a reliable means of quantifying tool-tip amplitude during in-process cutting, advancing the industrial readiness of UAD for aerospace applications.
