Mono-material sandwich structures for semi structural parts - combining lightweight with circularity goals

In times of resource depletion and climate change, conventional fiber-reinforced plastics in lightweight application are an essential component to meet climate goals, especially in application in motion. However, considering sustainability issues, circular economy and recycling of these materials show a significant disadvantage due to their hybrid composition. Therein, fiber shortening during mechanical recycling or critical substances in chemical recycling are two main concerns. One alternative approach is using self-reinforced composites, in which fiber and matrix are based on the same polymer family and therefore are predestined for recycling. By combining different material morphologies of one polymer like high tenacity fibers, bulk material, and foam to a sandwich structure, the lightweight potential of one single material is maximized. At first this paper introduces the mechanisms leading to a self-reinforcement, which are applicable to PP, PET and PLA. Finally, the focus is on the development of polyamide based self-reinforced sandwich structures for semi-structural parts within the EUREKA PassEnger project. Herein a short overview of the development of fibers, foam-cores, face-sheet production, sandwich manufacturing, part processing and recycling is given.