细胞壁多尺度分级结构中的界面相及其失效机制

The interface significantly influences the performance of composites such as strength, toughness and stabilization due to the stress transfer efficiency and failure modes of interface. And the ultrastructure of wood cell walls and its mechanism to the performance of composites have become a key scientific problem in the field of wood science. In this study, the cell wall of Masson pine wood was taken as the research object, and Nano probe techniques (Peakforce scanning and Nano IR) were introduced for directly measuring the interface mechanics and chemistry of graded-hierarchical structure in wood cell walls. Furthermore, Influence mechanism of graded-hierarchical structure on interface strength will be studied to reveal the fine variation of mechanical properties in the hierarchical structure of wood cell walls and the relationship between hierarchical structure and cell wall properties. And through building a relationship between interface thickness, interface bonding strength and stress transfer efficiency, to analyse the interface mechanism on the wood cell walls. Finally, to study the influence mechanism of cell wall graded structure on crack initiation, propagation and growth by Finite Element Analysis (FEA) of interface failure process. The achievement of the project will be also useful for the research and mechanical properties and failure mechanism of wood.

界面相决定了界面载荷传递效率以及界面破坏失效模式，对材料的强度、韧性及其稳定性都有着重要的影响；而解析木材细胞壁精细结构及其对材料性能的响应机制，已成为当今世界木材科学领域亟待解决的科学难题。本项目以马尾松木材细胞壁为研究对象，引进最新的纳米探针技术（Peakforce 和 Nano-IR）对细胞壁多尺度分级结构下的界面相开展力学和化学的表征技术研究，通过研究多尺度分级结构中界面结构对强度的影响机制，阐明木材细胞壁多尺度分级结构力学性能的精细变化规律，揭示其分级结构与细胞壁性能间的内在关系；建立细胞壁分级结构中界面相厚度、界面力学性能与界面应力传递效率之间的定量关系，揭示细胞壁界面相的界面作用机制；并通过有限元分析研究界面破坏过程，解析细胞壁分级结构对其裂纹萌生、扩展及长大的影响机制。本项目的研究成果对研究木材力学性质以及木材破坏机理分析具有重要的借鉴意义。

木材在实际使用过程中，受到外部载荷作用时通常会发生弯曲和受拉破坏，此外，木材破坏过程主要包括初始裂纹的萌生及裂纹扩展过程，其中易产生初始裂纹的部位称之为木材破坏过程中的弱相结构。为了深入探讨载荷作用下木材破坏过程中的弱相结构及裂纹扩展规律，本研究以马尾松为例，通过原位监测技术揭示了顺纹拉伸和弯曲作用下木材的起始破坏位置及裂纹扩展规律，精准定位了木材破坏过程中弱相结构；通过显微分析方法揭示了顺纹拉伸以及弯曲剪切应力作用下细胞壁破坏过程中的裂纹萌生及扩展规律，明确了不同破坏断面的细胞破坏类型；系统分析了早晚材管胞间力学性质差异、交叉区域管胞与射线间力学性质差异对木材结构破坏过程中的弱相结构及裂纹扩展的影响机制；阐明了细胞壁主要化学组分变形机制以及壁层间的应力传递规律对细胞壁结构破坏的影响机理。本项目的研究成果对研究木材力学性质以及木材破坏机理分析具有重要的借鉴意义。