Recovering Carbon Fibers

S ince 2000, the worldwide market for carbon-fiber-reinforced composite materials (CFRP) has grown from 30,500 to 43,500 tons per year. According to the latest estimates, the demand for carbon fibers will rise to some 1,300,000 tons by 2020 [1]. When preforms are used for manufacturing CFRP parts by the Liquid Composite Molding (LCM) process, up to 40 % waste accrues, resulting in a considerable economic loss. This textile waste currently serves as the main source of recycled fibers. Carbon fibers can also be recovered from end-of-life parts. However, since CFRP is a material that is relatively young to plastics processing, it will take years for the amount to become sizeable. Then, at the latest, will there be a need to have a suitable process available for recycling CFRP materials. The following investigations focus on the recovery of carbon fiber from end-oflife parts by means of microwave-aided pyrolysis. This research work at Fraunhofer ICT in Pfinztal, Germany, was aimed at developing a microwave pyrolysis oven by performing experiments on the pyrolysis of CFRP. Fibers obtained in this were compared with new fibers, as well as with fibers recycled by thermal pyrolysis; fiber surface and diameter were investigated under a scanning electron microscope. Measurements of strength, E-modulus and maximum strain on individual fibers supplement the characterization. State-of-the-Art