Processing of waste carbon and polyamide fibers for high-performance thermoplastic composites: Modifications to the auto-leveling system to enhance the quality of hybrid drawn sliver

The auto-leveling system of a modern draw frame is widely used for conventional fibers to develop homogeneous, uniform, and defect free drawn slivers. This auto-leveling system also improves the quality of tapes and hybrid yarn structures by eliminating mass irregularities in hybrid sliver. However, the existing auto-leveling system exerts very high loads on feedstock, thus diminishing the quality of waste carbon in the delivered sliver. The aim of the present study was to process hybrid sliver based on waste carbon and polyamide fibers on a modern draw frame and modify the auto-leveling system to enable the damage-free processing of carbon fiber. For this purpose, hybrid card slivers were processed on an industrial draw frame with auto-leveling system. The different auto-leveling parameters, e.g., scan roller width and scan roller load, were modified and optimized for the uniform and damage-free processing of hybrid sliver. Results revealed that the scan roller load has a significant influence on the quality of waste carbon fiber in hybrid sliver. A uniform hybrid sliver ensures the reproducibility of unidirectional tapes and hybrid yarn at industrial scale, while simultaneously maintaining the quality of recycled carbon fiber-reinforced thermoplastics.