Experimental feasibility and environmental impacts of compression molded discontinuous carbon fiber composites with opportunities for circular economy

Compression molding of carbon fiber sheet molding compounds (CF-SMC) is a promising technology to reduce the waste of carbon fiber composites and to drive sustainable development in lightweight applications. Both, the production waste of prepreg scrap and the end-of-life waste of carbon fiber components can be used efficiently in the recycling process with an apparent sandwich structure of virgin and recycled materials. This contribution investigates the technology on the example of a structural automotive component (transmission crossmember). A one-shot compression molding process was developed which enables cost-efficient, large-scale manufacturing with cycle times of about two minutes. The process-structure-property-performance relationship was experimentally characterized with manufacturing studies and prototype tests. A multilayered hybrid structure of virgin and recycled carbon fiber materials maintains the manufacturability and the mechanical performance compared to primary CF-SMC. The environmental impacts were assessed within a comparative life cycle assessment (LCA). Different material and recycling scenarios were analyzed for the components produced. It revealed lower environmental impacts than an industrially used reference version in aluminum in most impact categories. The combination of the compression molding technology with multilayered hybrid carbon fiber composites reveals opportunities for circularity and the multistage use of industrial recyclates for varying quality requirements in lightweight applications.