Abstract: "Carbon fiber composites are recognized as a critical strategic material due to their exceptional properties, such as light weight, high strength, and corrosion resistance, demonstrating significant potential for civil applications. To promote the development of carbon fiber composites in civil fields, reducing costs has become imperative, making large-tow carbon fiber composites the primary choice. With the advancement of pultrusion technology, pultruded composites have been widely used in civil applications. To enable the application of pultruded composites in civil fields, especially in rail transportation, and to enhance the core competitiveness of China's high-speed rail vehicles in terms of low cost and lightweight development, higher requirements have been placed on the dimensions and cross-sectional shapes of pultruded composites. Therefore, the fabrication of large-tow carbon fiber pultruded multi-cavity profiled beams provides a viable solution to meet these demands. Traditional pultrusion processes often uses yarns as reinforcement materials, resulting in products with simple structures and significant differences in longitudinal and transverse mechanical properties, which cannot meet the needs of multi-field applications. Currently, a small number of researchers have begun to explore the use of multi-axial warp-knitted fabrics as reinforcement materials to fabricate multi-cavity profiled composites and have verified the feasibility of applying fabric-reinforced pultruded composites to rail transportation vehicles. However, most of these studies focus on testing entire components, with relatively limited research on the uniformity of mechanical properties in different parts of the components and the factors influencing them. In this paper, multi-axial warp-knitted fabrics made of large tow carbon fibers were used as reinforcement materials. Taking high-speed rail components as an example, a multi-cavity profiled beam structure was designed, and a detailed layup and resin injection scheme was formulated. The multi-cavity profiled beam was then prepared through the pultrusion process. Seven regional cavity walls were selected based on variations in layup and resin injection volume. The thickness, fiber volume fraction, and porosity of the cavity walls in these seven different regions were measured to assess the uniformity of the molded parts and analyze the causes of deviations. Additionally, the tensile, compressive, and interlaminar shear tests were conducted on different cavity walls to analyze the failure modes and the reasons for differences in mechanical properties. The results show that the mechanical properties of the multi-cavity profiled beams successfully prepared using the fabric pultrusion process are closely related to the fiber volume fraction, and the mandrel is a critical factor causing dimensional deviations. This study not only provides data reference for the subsequent preparation of multi-cavity profiled pultruded composites, but also holds significant importance for promoting the further application of composites in fields such as rail transportation."

Key words: large-tow carbon fiber, multi-axial warp-knitted fabric, pultrusion, multi-cavity profiled, composites

摘要： 为了促进拉挤成型复合材料在多领域的应用，以大丝束碳纤维多轴向经编织物为原料，采用拉挤成型工艺制备了大丝束碳纤维织物多腔异型梁复合材料，测量了不区域腔壁的厚度、纤维体积含量及孔隙率，根据腔壁的位置选择了7个区域进行了拉伸、压缩和层间剪切测试，并分析了不同腔壁力学性能产生差异的原因。结果表明：拉挤多腔异型梁复合材料各腔壁的力学性能与纤维体积含量及纤维取向相关，且芯棒是导致各腔壁尺寸偏差的关键因素。研究结果可为后续多腔异型拉挤复合材料的制备工作提供数据参考

关键词: 大丝束碳纤维, 多轴向经编织物, 拉挤成型, 多腔异型, 复合材料