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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.

Carbon fiber reinforced cyclic butylene terephthalate composites have been processed by vacuum infusion under two different non-isothermal processing routes starting from a one-component cyclic butylene terephthalate resin system. One of them was processed under a short cycle with fast cooling, and another one was processed under a long cycle with slow cooling. Both the micro-structure and low-energy impact properties of the composites have been investigated. On one hand, the fast cooling generates randomly dispersed voids and porosities in the resin-rich regions during the crystallization-induced shrinkage. On the other hand, the slow cooling generates a highly crystalline and brittle matrix without porosity. However, many micro-cracks appear in the resin-rich regions due to the combination of the brittleness and longitudinal shrinkage of the matrix. The critical delamination energy of the slow cooled composite is slightly higher than that of the fast cooled one, whereas this latter absorbs over 25% more energy before being penetrated, as well as performing in a less brittle way. The lower interlaminar shear strength of the fast cooled composite is suggested to be the origin of its higher energy absorbing capability and less brittle behavior.

Carbon fiber reinforced epoxy composites were successfully manufactured by a new compression resin transfer molding process. The main innovation is that the injection stage is vacuum assisted. The high fiber volume fraction and low void content are promising properties for structural applications. The samples were tested under instrumented falling weight impact loading. Based on the contact time and delamination plots, the damage initiation energy threshold has been found to be 1.42 J, and from the energy plot a 30.25 J penetration energy threshold is deduced. Damage propagation is more energy dissipative process than the initiation one, since the ductility index takes a value of 1.97.

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