Recycling of Discontinuous Long Fibre Thermoplastic Composites

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Composite materials continue to replace metal in a growing number of applications due to their recognized performance, tailorability, and manufacturing advantages. While continuous fibre composites are the primary materials employed to replace metallic components in aerospace applications, their current use is generally limited to large shell-like structures. There is thus an emerging interest in the aerospace industry to use composite materials at a smaller scale to replace complex-shaped metallic components. Lying between traditional continuous fibre composites and short-fibre injected plastics are Discontinuous Long Fibre (DLF) composites, a bulk moulding compound type of material comprised of randomly oriented chips of prepreg tape that can be compression moulded into complex-shaped parts. This process is a very attractive candidate for the replacement of metallic parts, as it offers the possibility to produce net-shaped components having complex features. By producing net or near-net shape parts, material waste is considerably reduced, while the need for traditional post-moulding operations such as cutting, trimming and/or drilling is practically eliminated. Moreover, recent studies have demonstrated that DLF thermoplastic composites have potential to be fully recyclable. However, the development of such a technology is not trivial, mainly due to the challenges involving the processing of DLF composite parts. The main objective of the proposed research program is to develop a robust processing scheme for efficient recycling of polymer composites. The material system will consist of thermoplastic prepreg tape, which is increasingly used in aerospace applications. Using a framework that includes processing and characterization, a methodology will be developed to evaluate the effect of key processing related characteristics on the quasi-static and fatigue behaviour of two types of recycled DLF composites. The findings of this study will help determine the main drivers to take into account during the design and manufacturing of recycled DLF composite parts. The proposed program will develop new processing methods and process control technologies to further increase the life cycle and sustainability of thermoplastic composites.