Carbon fibre-reinforced plastics (CFRP) are widely used in aerospace, automobile and
other structural applications due to their superior mechanical and physical properties.
CFRP outperform conventional metals in high strength-to-weight ratio. Usually, CFRP
parts are manufactured near to net-shape;however,machining is unavoidable when it
comes to assembly. Drilling the holes are essential to facilitate riveting and bolting of
the components. However, conventional drilling (CD) induces different types of
damages such as cracking, fibre pull-out, sprintling and delamination due to the
abrasive nature, inhomogeneity and anisotropy of CFRP. A novel technique,
ultrasonically-assisted drilling (UAD) is hybrid machining technique in which highfrequency
(typically above 20 kHz) vibration are superimposed on a standard twist drill
bit in axial direction using ultrasonic transducer. UAD has shown several advantages
such as thrust force reduction, improving surface quality and lower bur-formation in
drilling of conventional metals. UAD has also effectively been used for drilling brittle
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.
Wolfson School of Mechanical and Manufacturing Engineering