竹材维管束梯度结构环向应力-应变行为的协同变形机制

The bamboo based pipe products has been widely adopted in the fields of water conservation, agriculture, forestry and housing construction, which is good alternative for plastic, galss fiber reinforced plastics, steel pipes and concrete pipes. The structure optimization and performance improvement for bamboo pipe products rely on understanding the mechanism of bamboo’s stress-strain behaviors as well as the application of key technique. The objective of this project is to investigate how bamboo’s unique vascular gradient structure affects its circumferential stress-strain behaviors through using the advanced analytical techniques in both nano and micro scales. The thin bamboo strip was compared with those impregnated with resin. The effect of coordinated shape-shifting between bamboo vascular and parenchymatous tissue on the high-strength and high-stiffness will be identified. High-resolution imaging technique will be used to analyze the microstructure of the interface between bamboo gradient structure and resin under circumferential direction. The effect of combination state between bamboo vascular, parenchymatous tissue and immersed resin on circumferential bending interface will also be identified. The relationship between the bending stress-strain behaviors under the vascular gradient distribution and the characteristics of circumferential interface will be explored from the multi-level and multi-scale perspectives. The proposed project will be beneficial to expanding applications of bamboo resources. It will provide a base for the design and manufacture of high-performance bamboo based composite pipe products.

竹缠绕生物基复合管（BCPP）可替代塑料、玻璃钢、钢材和水泥管道，在水利、农业、林业、住建等领域得到广泛应用，竹材弯曲状态下的应力-应变行为及其与环向树脂界面结合特性是关系BCPP结构优化与性能提升的关键因素。本项目针对竹材维管束梯度分布的结构特点，以浸渍和非浸渍树脂的薄竹篾材为研究对象，采用先进的纳微观分析手段，研究环向加载下竹材应力-应变行为特征，揭示竹维管束、薄壁组织协同变形对高强高柔韧性的贡献机理；研究环向状态下竹材梯度结构与树脂界面高分辨率成像特征及微区力学性能，阐明竹维管束、薄壁组织与浸渍树脂结合状态对环向弯曲界面的作用机制；从多层次、多尺度建立竹材梯度结构弯曲状态下应力-应变行为与环向树脂结合界面特性的内在关系，为结构-功能一体化、高性能竹缠绕复合新材料的设计与制造提供物理学基础，对拓展竹材资源应用领域具有重要意义。

竹材柔韧性是竹学基础研究领域的热点科学问题之一，系统深入地评价竹材柔韧性对竹缠绕复合材料、竹编织、竹质曲面异型家具和竹纤维深度模压等高附加值创新产品的开发具有重要意义。本项目以毛竹篾为研究对象，提出了采用压弯法与挺度法相结合的竹篾柔韧性表征新方法，获得了挺度法、三点弯法、压弯法三种方法的适用范围。从解剖结构、物理性质和化学组成等方面研究竹材高强高柔韧性的贡献机制，结果表明：竹材高弯曲柔韧性与组织水平上维管束梯度分布、细胞水平上纤维-薄壁细胞协同变形以及在亚细胞水平上水分子对细胞壁层和胞间层的润滑作用均有密切关系。在纳米尺度上，竹子的柔性机制是通过纤维素无定形区域的分子链展开和纤维素微纤维与木质素-碳水化合物复合物 (LCC) 之间界面的分子间滑动来实现的；细胞水平上，纤维和薄壁细胞形态的协同变形贡献了高柔韧性机制；宏观尺度上，纤维拔出和裂纹扩展是竹材主要的增韧机制。在此基础上，探索了含水率、热处理、浸渍处理、碱处理等多种外界因素对竹材柔韧性的影响机理，细胞壁改性后的分子链和细胞间层/壁层弱界面对竹材柔性/韧性的增强/抑制作用。充分发挥竹材优异的柔韧性，创新开发了一种天然的高稳定性竹螺旋弹簧材料，具有减震储能等优势。相关研究结果发表于国内外知名刊物《Industrial Crops and Products》、《Journal of Materials Research and Technology》、《Journal of Wood Science》、《Forests》、《Materials》及《林业工程学报》等，并多次在国内外行业学术研讨会上进行学术交流。