The Japanese perennial knotweed (Fallopia japonica) is a globally widespread neophyte whose usability is being investigated, e.g., to use knotweed for biogas plants and as a substitute for firewood. The present study investigates the potential of Japanese knotweed for material use. Morphological studies were carried out on the stem cell structures and arrangements (microstructure) and the external stem structure (macrostructure) and showed that Japanese knotweed is a plant species with several hierarchical morphological levels being a highly complex fibre-matrix composite with a low density. Mechanical properties were investigated using tensile, bending, compression and impact tests for fresh and dry specimens and then mathematically converted in density-related lightweight construction indices and compared with other materials using Ashby maps. Particularly under compression, properties are close to woods and wood composites, making the plant an interesting material for lightweight sandwich panels, where assembled slices of the stalk could serve as core elements. Fibre bundles, extracted from the stalk, show relatively low mechanical properties (tensile strength: 93 MPa; Young’s modulus: 4.77 GPa) compared to bast fibres such as hemp. The shredded stalks could be compounded into homogeneous granulates directly after harvesting without other separation processes. Therefore, the study presents a proof of concept for Japanese knotweed to apply the shredded stalks in injection-moulded PLA composites (tensile strength: mean = 54 MPa; Young’s modulus: mean = 5.61 GPa) comparable or even better than wood fibre-reinforced polymers.

日本多年生虎杖（Fallopia japonica ）是一种全球广泛分布的新植物，其可用性正在研究中，例如，将虎杖用于沼气植物和作为木柴的替代品。本研究调查了日本虎杖作为材料使用的潜力。进行了形态学研究干细胞结构和排列（微观结构）和外部茎结构（宏观结构），并表明日本虎杖是一种具有多个层次形态水平的植物物种，是一种高度复杂的低密度纤维基质复合物。机械性能通过对新鲜和干燥试样的拉伸、弯曲、压缩和冲击试验进行研究，然后在与密度相关的轻质结构指数中进行数学转换，并使用 Ashby 图与其他材料进行比较。特别是在压缩条件下，其特性接近木材和木材复合材料，使植物成为轻质夹芯板的有趣材料，其中组装的茎片可以作为核心元件。从茎中提取的纤维束显示出相对较低的机械性能（抗拉强度：93兆帕; 杨氏模量：4.77 GPa）相比麻等韧皮纤维。切碎的茎秆可以在收获后直接复合成均匀的颗粒，无需其他分离过程。因此，该研究为日本虎杖在注塑成型的 PLA 复合材料（抗拉强度：平均 = 54 MPa；杨氏模量：平均 = 5.61 GPa）中应用切碎的茎秆提供了概念验证，与木纤维增强聚合物相当甚至更好.