On the manufacturing defects of thermoplastic carbon/epoxy composites manufactured by automated tape placement

Thermoplastic composites are highly recommended for structural application, not only for their superior characteristics derived from the fiber and matrix materials but also for their recycling possibilities, which is a major issue in the today's engineering practice. The manufacturing techniques for thermoplastics are different from those for the well-established thermoset composites. This paper addresses the quality of the thermoplastic composites by assessing the distribution of the fiber, the void contents and the waviness of the fibers, compared to the thermoset composites. IM7/PEEK and AS4/PA12 are the two thermoplastic composite systems used for this study, whereas, IM7/8552 is the thermoset composite used as reference. The specimens were examined using optical microscopy and computed tomography (CT) and the results were statistically treated using circular statistics. Compared to the IM7/8552 composite, the analysis reveals that the IM7/PEEK and AS4/PA12 composites, manufactured by ATP result in a higher volume of voids. On the other hand, ATP processing improves the alignment of the fibers, as the solidification process occurs while the fibers are in tension. The microscopy studies also show that the ATP manufactured composites have an area in between the different layers of tape with a low number of fibers, compared to the other areas.