The emergence of new high-performance thermoplastics to replace thermosets in fiber-reinforced polymers puts up a new challenge: their machining. In this study, carbon fiber-reinforced poly-cyclic butylene terephthalate laminates were manufactured, drilled, and inspected. Different commercial drill geometries and machining conditions were compared. Roughness, microscopy, and non-destructive tests allowed us to determine the hole quality as well as delamination. The surface tests showed better results after working at the most common cutting speed (3000 rpm) than at high speed (15,000 rpm) with a constant feed rate.
This fact can be explained based on the viscoelastic properties of the matrix that becomes fragile at high cutting speeds. The Delamination factor obtained by means of Ultrasonics and X-ray Computed Tomography also confirmed that the best results are achieved with a Twist drill bit at 3000 rpm. In contrast to carbon fiber-reinforced thermosets, the detected delamination at high cutting speeds is not as remarkable as expected. These results allow us to conclude that this new composite will certainly increase production rate without delamination damage. Chip formation takes also a special role. It can be recovered to be used as reinforcement in manufacturing processes due to the recyclability of the thermoplastic matrix.
