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    Item-typ:Veröffentlichung,
    Novel Low-Twist Bast Fibre Yarns from Flax Tow for High-Performance Composite Applications
    The use of natural fibres for components subjected to higher mechanical requirements tends to be limited by the high price of high-quality semi-finished products. Therefore, the present study deals with the development of more cost-effective staple fibre yarns made from flax tow. In the subsequent processing stage, the yarns were processed into quasi-unidirectional (UD) fabrics. The results of the fibre characterisation along the process chain have shown that no significant mechanical fibre damage occurs after slivers' production. Fibres prepared from yarns and fabrics show comparable characteristics. The yarns were processed to composites by pultrusion to verify the reinforcement effect. The mechanical properties were comparable to those of composites made from a high-quality UD flax roving. The fabrics were industrially processed into composite laminates using a vacuum infusion and an autoclave injection process (vacuum injection method in an autoclave). While impact strength compared to a reference laminate based on the UD flax roving was achieved, tensile and flexural properties were not reached. An analysis showed that the staple fibre yarns in the fabric show an undulation, leading to a reorientation of the fibres and lower characteristic values, which show 86-92% of the laminate made from the flax roving. Hybrid laminates with outer glass and inner flax layers were manufactured for the intended development of a leaf spring for the bogie of a narrow-gauge railroad as a demonstrator. The hybrid composites display excellent mechanical properties and showed clear advantages over a pure glass fibre-reinforced composite in lightweight construction potential, particularly flexural stiffness.
    Wissenschaftlicher Artikel
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      87
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    Item-typ:Veröffentlichung,
    Unidirectional Tape‐Based Composites from Hemp and Pineapple Leaf Fiber: Mechanical Performance in Conventional and Bio‐Based Matrices
    (Wiley, 2025-12) ; ;
    Ackermann, Valentin
    ;
    Baumann, Roja M.
    ;
    Bischoff, Corvin
    A newly developed unidirectional semi-finished product made from hemp or pineapple leaf fibers (PALF) is examined for its reinforcing potential in various polymer matrices, including epoxy, bio-based epoxy, polyhydroxyalkanoate (PHA), polybutylene adipate terephthalate (PBAT), and polylactide (PLA), at a fiber volume fraction of ≈40%. Compression-molded composites are characterized with respect to mechanical properties, interlaminar shear strength (ILSS), density, and void content. All systems show promising performance, with tensile strengths ranging from 110 MPa for PALF/PHA to 227 MPa for hemp/bio-based epoxy, and Young's moduli ranging from 9.8 to 22.7 GPa. At comparable ILSS levels, hemp-based composites exhibit higher strengths and stiffnesses, whereas PALF composites show increased void content. The observed microvoids appear less detrimental than macrovoids, supporting the materials’ suitability for lightweight structures. PALF composites demonstrate greater toughness than their hemp counterparts, with PALF/bio-based epoxy achieving an unnotched Charpy impact strength of 39 kJ m−2 compared with 29 kJ m−2 for hemp/bio-based epoxy. Although the full tensile strength potential of PALF cannot be realized—because the composites do not reach the fibers’ maximum elongation and therefore their maximum stress—the combination of low density and favorable mechanical behavior highlights both PALF and hemp-based composites as promisi ng candidates for structural lightweight applications.
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