利用扫描电镜原位拉伸研究竹材增韧机制

为了阐明竹材优良韧性的力学原理，以毛竹为研究对象，使用扫描电镜联用原位加载设备观察了竹材薄片纵向拉伸过程的裂纹扩展规律，并对断裂表面进行了组织水平、细胞水平、亚细胞水平的多尺度显微观察。结果表明:竹材纵向拉伸断裂裂纹拓展一般呈阶梯型展开。维管束与基本组织之间、竹纤维与薄壁组织细胞之间、纤维和薄壁细胞的壁层之间均有明显的分层现象，表明竹材断裂过程中存在从组织到细胞，乃至亚细胞水平的多级弱界面。这些弱界面可以有效阻碍裂纹扩展，增加断裂消耗功，从而显著增强竹材的韧性。 

Toughness mechanism of bamboo by in-situ tension

In order to reveal the toughening mechanism of bamboo,micro-tensile test combined with scanning electron microscopy ( SEM ) was used to observe its in-situ crack propagation process during tension. Furthermore,high resolution field emission gun ( FEG) SEM was applied to study the consequent fracture surface with different magnification. The results showed that the micro-crack in the bamboo followed the way of "zigzag"during longitudinal tension,in addition to the frequently observed delamination located between vascular bundles and parenceymal cells,among bamboo fibers or parenchymal cells,and even between the lamellae in the cell wall of fibers or parenchymal cells. All the above observations pointed to the existence of multi-scale weak interface from tissue,cell to sub-cellular level in bamboo,which could increase the toughness of bamboo by blocking the growth of cracks and maximizing the work to fracture.