Forced conveying as a novel method for spreading fiber rovings

Unidirectional fiber-reinforced thermoplastic (UD) tapes are used increasingly in lightweight construction for local reinforcement of plastic parts. A critical step in UD tape manufacturing is spreading of the fiber rovings by mechanical, electrostatic, pneumatic, or acoustic means to obtain a homogeneous carpet. This is a prerequisite for homogeneous impregnation, which in turn is a requirement for defect-free reinforced components. A major challenge in fiber spreading is the inconsistent and scattering width of the fiber rovings within a bobbin or between different bobbins caused by the manufacturing process of the rovings. Especially for heavy tows – carbon-fiber rovings consisting of more than 24K filaments – variable input quality of the rovings renders obtaining a constant final roving width with existing spreading techniques impossible. We propose a novel spreading technique based on the principle of forced conveying that aims to provide constant final widths that are largely independent of the quality of the input roving. In a feasibility study, we investigated the forced conveying spreading behavior of a 60K carbon fiber roving; our new spreading method provided constant final widths independent of initial width and cross-sectional shape. Statistical analysis showed that both the wrap angle and the circumferential speed of the roller and their quadratic influences have highly significant effects on the final spread width. With an {R}² of 0.9972, the quadratic model determined has good predictive accuracy for the spread width in the measured range.