Entwicklung und Evaluierung eines neuartigen Recyclingverfahrens für thermoplastische Tapes ; 1. Auflage

Fiber-reinforced plastics (FRP) are characterized by their high strength combined with low weight and are therefore a preferred material for a wide range of lightweight construction applications in various industries. Unidirectional fiber-reinforced plastics are used in high-tech applications with demanding performance requirements, such as in the aerospace industry and the high-pressure vessel industry. The production of these raw materials, especially carbon fibers, requires a high amount of energy and therefore causes significant greenhouse gas emissions. A circular economy based on high-quality recycling of resources offers today's industrialized nations potential for cost reduction and growth. At the same time, this approach helps to minimize environmental impact. The opportunities and challenges of the FRP recycling industry are illustrated in this thesis by analyzing the security of supply, the political framework and the economic drivers. The development of the circular economy in the field of fiber-reinforced plastics is still in an early stage. The current state of recycling technologies is analyzed in a review on the state of science and technology. Although existing industrial recycling processes require less energy than the production of new fiber-reinforced plastics, the fibers can only be recovered in a shortened and disordered form with reduced strength. As a result, these fibers are unsuitable for use in high performance products. Consequently, there is a need for recycling technologies that are designed to overcome these limitations. Since 2018, the Fraunhofer-Gesellschaft is in possession of a patent for a recycling process that permits the recovery of unidirectional fiber-reinforced, tape-shaped thermoplastic semi-finished products (tapes) without shortening the length of the fibers or losing the orientation of the fibers. In this thesis, a process strategy for the recycling process will be developed, which is the fundament for the development and validation of a test rig. In addition to the recycling process, the properties of the recovered material are relevant to demonstrate the feasibility of high-quality recycling. The reusability of the recycled material is demonstrated for automated tape winding and hot press molding processes. The mechanical performance of test specimens made from recycled material is compared with those made from virgin material. This PhD thesis elaborates the basis for a novel, sustainable and effective recycling strategy for fiber-reinforced plastics that offers both ecological and economic benefits.