Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China; Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China.
Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China; Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China; The Collaborative Innovation Center for Advanced Aero-Engine (CICAAE), Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China.
Acta Biomater. 2018 Jan;65:203-215. doi: 10.1016/j.actbio.2017.10.005. Epub 2017 Oct 5.
Natural bamboo with different water weight contents (0%, 6% and 22%) had distinguishingly different mechanical properties, where samples with water contents of 22% had tensile strength and elongations increased by ∼30% and ∼200% than the dry (0%), respectively. The deformation and fracture process was synchronously recorded and analyzed with the aid of the acoustic emission (AE), during which there were three kinds of real time fracture behaviors recognized: matrix (multi-walled parenchyma cells) failure, interfacial (fiber/fiber or fiber/parenchyma cell walls) dissociations and fiber breakage. More interfacial dissociations and higher fracture energy were detected as more water was added, since water molecules can make great differences on the bamboo's inner micro-structures and the mechanical properties. During the fracture process of the wet bamboo detected by AE, matrix failure and interfacial dissociations contributed most of the elongation, and the strength were mainly depended on the fiber breakage and interfacial dissociations. The discovered structural toughening mechanisms within the multi-scaled structures were microfiber bridging, multi-walled fiber pull-out, micro warts buckling and crack deflection. The micro-structural toughening effects were strengthened by the cellulose-hemicellulose-lignin complexes and a certain content of water molecules within the multi-scaled fibrous cellular structures, which are collaboratively working and ensuring the high mechanical performance of the natural bamboo.
The mechanical behaviors during the whole fracture process of bamboo were investigated by acoustic emission (AE). During the fracture process there were three kinds of fracture behaviors recognized by AE: matrix (parenchyma cells) failure, interfacial (fiber/fiber or fiber/parenchyma cell walls) dissociations and fiber breakage. The mechanical performance was greatly influenced by water contents (0%, 6% and 22%). Wet bamboos had higher fracture energy than the dry ones. There was more interfacial dissociation behaviors detected as more water was absorbed within the multi-scaled structures. The micro structural toughening mechanisms were strengthened by the macromolecular complexes and water molecules, which are working together and ensuring the excellent mechanical properties of the natural bamboo.
不同含水量（0%、6%和 22%）的天然竹子具有明显不同的机械性能，其中含水量为 22%的样品的拉伸强度和伸长率分别比干燥（0%）时增加了约 30%和 200%。借助声发射（AE），同步记录和分析了变形和断裂过程，在此过程中，识别出了三种实时断裂行为：基体（多壁薄壁细胞）失效、界面（纤维/纤维或纤维/薄壁细胞壁）分离和纤维断裂。随着水分的增加，检测到更多的界面分离和更高的断裂能，因为水分子对竹子的内部微观结构和机械性能有很大的影响。在 AE 检测到的湿竹断裂过程中，基体失效和界面分离对伸长贡献最大，而强度主要取决于纤维断裂和界面分离。在多尺度结构内发现的结构增韧机制包括微纤维桥接、多壁纤维拔出、微疣屈曲和裂纹偏转。纤维素-半纤维素-木质素复合物和多尺度纤维细胞结构内一定含量的水分子增强了微观结构增韧效果，它们协同工作，确保了天然竹子的高机械性能。
通过声发射（AE）研究了竹子整个断裂过程中的力学行为。在断裂过程中，通过 AE 识别出了三种断裂行为：基体（薄壁细胞）失效、界面（纤维/纤维或纤维/薄壁细胞壁）分离和纤维断裂。含水量（0%、6%和 22%）对力学性能有很大影响。吸水后的湿竹具有更高的断裂能。在多尺度结构内吸收更多的水分时，检测到更多的界面分离行为。微观结构增韧机制是由大分子复合物和水分子增强的，它们共同作用，确保了天然竹子优异的力学性能。
