Multifunctionality of polymer composites based on recycled carbon fibers: A review

Carbon fiber reinforced polymers (CFRP) offer outstanding lightweight potential and can play a key role for modern energy and mobility concepts. However, production of carbon fibers is energy- and cost-intensive, while at the same time waste rates of common manufacturing technologies are quite high and repair possibilities for damaged parts still limited. Therefore, holistic recycling approaches are urgently required in order to reach acceptable cost-efficiency and sustainability. What makes the recycling so challenging, is the fact that true recycling, i.e. re-usage of fibers in high-performance composites, requires preservation of a high fiber length and enabling of accurate fiber orientation. This generates a trade-off between the best possible exploitation of the fiber properties and the effort to minimize the recycling costs. Hence, this paper does not only give a brief overview of technologies to recover carbon fibers from waste and to process them to new CFRP components. In addition, different approaches are presented, that exploit the specific characteristics of semi-finished products based on recycled carbon fibers, in order to achieve process- or material-related multifunctionality. This includes quasi-plastic deformation behavior (enables deep-drawing or curved tow placement), improved surface quality through reduced fiber print-through, robust resin impregnation through supersaturated nonwovens, and high energy absorption.