Ogawa Fumio, Liu Fan, Hashida Toshiyuki
Fracture and Reliability Research Institute, Tohoku University, 6-6-11, Aza-Aoba Aramaki, Aoba-ku, Sendai-shi 980-8579, Japan.
Materials (Basel). 2023 Feb 19;16(4):1725. doi: 10.3390/ma16041725.
Carbon nanotubes (CNTs) exhibit high strength, Young's modulus, and flexibility and serve as an ideal reinforcement for composite materials. Owing to their toughness against bending and/or twisting, they are typically used as fabric composites. The conventional multiaxial braiding method lacks tension and resultant strength in the thickness direction. Some braiding patterns are proposed; however, they may have shortcomings in flexibility. Thus, this study proposed three types of braiding pattern for fabrics based on natural products such as spider net and honeycomb, in accordance with thickness-direction strength. The spider-net-based structure included wefts with spaces in the center with overlapping warps. At both sides, the warps crossed and contacted the wefts to impart solidness to the structure and enhance its strength as well as flexural stability. In addition, box-type wefts were proposed by unifying the weft and warps into boxes, which enhanced the stability and flexibility of the framework. Finally, we proposed a structure based on rectangular and hexagonal shapes mimicking the honeycomb. Moreover, finite element calculations were performed to investigate the mechanisms through which the proposed structures garnered strength and deformation ability. The average stress in fabrics becomes smaller than half (43%) when four edges are restrained and sliding is inserted. Under three-dimensional forces, our proposed structures underwent mechanisms of wrapping, warping, sliding and doubling, and partial locking to demonstrate their enhanced mechanical properties. Furthermore, we proposed a hierarchical structure specialized for CNTs, which could facilitate applications in structural components of satellites, wind turbines, and ships. The hierarchical structure utilizing discontinuity and sliding benefits the usage for practical mechanical systems.
碳纳米管（CNTs）具有高强度、杨氏模量和柔韧性，是复合材料的理想增强材料。由于其抗弯曲和/或扭曲的韧性，它们通常用作织物复合材料。传统的多轴编织方法在厚度方向上缺乏张力和强度。人们提出了一些编织图案；然而，它们在柔韧性方面可能存在不足。因此，本研究根据厚度方向的强度，提出了三种基于蜘蛛网和蜂窝等天然产物的织物编织图案。基于蜘蛛网的结构包括中心有空隙且经纱重叠的纬纱。在两侧，经纱交叉并与纬纱接触，使结构更坚固，增强其强度以及弯曲稳定性。此外，通过将纬纱和经纱统一成盒子的方式提出了盒式纬纱，增强了框架的稳定性和柔韧性。最后，我们提出了一种模仿蜂窝的基于矩形和六边形的结构。此外，还进行了有限元计算，以研究所提出的结构获得强度和变形能力的机制。当四条边受到约束并插入滑动时，织物中的平均应力小于一半（43%）。在三维力作用下，我们提出的结构经历了包裹、翘曲、滑动和加倍以及部分锁定的机制，以展示其增强的力学性能。此外，我们还提出了一种专门针对碳纳米管的分层结构，这有助于在卫星、风力涡轮机和船舶的结构部件中应用。利用不连续性和滑动的分层结构有利于实际机械系统的使用。
