Development of yarns from recycled carbon fiber based on friction spinning technology with specific properties for thermoset composites

Abstract

Because of a growing demand and usage of carbon fiber, effective methods to re-use waste and recycled carbon fiber recoverable either from process scraps or from end-of-life components are attracting increased attention. The development of different hybrid yarn structures consisting of recycled carbon fiber and thermoplastic fibers (recycled carbon fiber content approx. 50% by weight) for thermoplastic composites have been reported earlier. Yarns with high recycled carbon fiber content (>90% by weight) required for thermoset composites are still not realizable due to high shortening in recycled carbon fiber length (≥70%) during different processing steps of spinning. The reason lies in low shear strength, smooth fiber surface and high brittleness of recycled carbon fiber. Second, a lack of crimp in recycled carbon fiber leads to drafting errors during the drawing and spinning process. In this paper, the spinning limit regarding the core to sheath ratio of noble yarns with a recycled carbon fiber content greater than 90% by weight based on friction spinning technology for thermoset composites is reported. Slivers of recycled carbon fiber solely required for the development of yarns are produced on carding and drawing machines optimized for the gentle processing of recycled carbon fiber. Furthermore, different spinning parameters such as spinning drum speed and suction air pressure are investigated and their effect on tensile properties of yarn is analyzed. The results show that yarns with high recycled carbon fiber content (>90% by weight) can be produced with reproducible quality on the DREF-3000 friction spinning machine.