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The development of innovative bio-based composites with efficient manufacturing processes is the purpose of the current project C4 in the framework of the Excellence Cluster MERGE EXC 1075, funded by DFG (Deutsche Forschungsgemeinschaft). Efficiency in terms of mass-production, reproducibility and flexibility requires the performance of successive steps in the manufacture of semi-finished and final bio-based products. About bio-based materials, natural fibres composite (NFC) prepregs have been recently investigated as a potential cost-efficient semi-finished product. By means of continuous production processes, prepreg rolls can be manufactured with unidirectional natural fibres (flax) fabrics as reinforcement and thermoplastic biopolymers films as matrix. The used natural fibre non-crimp fabrics are made of high twisted yarns. For a better impregnation and higher stiffness properties, non-crimp fabrics with non-twisted yarns, which have been lastly developed by natural fibres suppliers, represent an appropriate solution. A second suitable option is the substitution of the biopolymer films, whose impermeability does not facilitate the release of humidity from the natural fibres while the impregnation, by produced low cost thermoplastic spunlace fabrics with a higher permeability and lower reachable surface weights. With these material developments and innovative process optimizations suitable to natural fibres, NFC prepreg properties tend to be improved. From prepregs to finished parts can be implemented by discontinuous processes, with compression molding and back-injection molding, or by continuous processes, with devices gathering several stages such as cutting, stacking, points welding, pre-heating and back injection molding. By stacking, a multi-axial orientation of prepregs can be performed in order to optimize the placement of reinforcing yarns according to the possible load path of future products. The mechanical properties profile of the combination of non-crimp natural fibres fabrics with thermoplastic films or thermoplastic spunlace fabrics has been here studied in detail with press-engineered samples and has confirmed the potential as an alternative to glass fibre-reinforced composite.

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