木材多尺度结构的干缩湿胀研究进展

Research Development of Shrinkage and Swelling of Wood with Multi-Scale Structures

木材干缩湿胀是影响木材加工利用的关键特性,与木制品尺寸和形状的稳定性密切相关。木材宏观到微观层次分明的多尺度分级结构导致木材干缩湿胀行为的复杂性。将木材干缩湿胀研究从宏观尺度引向介观和微观尺度,建立三者之间的有机联系,有助于阐明木材干缩湿胀行为的发生机制和演变机理,对深入认识木材性质,合理、高效利用木材具有重要理论价值和实践意义。本研究综述木材宏观尺度(无疵试样)、介观尺度(生长轮)和微观尺度(木材细胞)3种层级单元的干缩湿胀行为及其滞后现象,分析木材不同尺度结构的干缩湿胀行为发生和演变规律,介绍基于多尺度结构的木材干缩湿胀测试方法和技术手段。同时,对今后开展木材多尺度结构干缩湿胀行为研究提出建议:1)在介观和微观尺度上系统开展针叶材和阔叶材基于生长轮和木材细胞的干缩湿胀行为研究,建立木材多尺度结构与干缩湿胀行为之间的构效关系;2)揭示基于各向异性、非均质性和细胞类型多样性引发的干缩湿胀行为差异化响应规律及其互作机制;3)阐明木材干缩湿胀行为的时间滞后和湿胀滞后现象;4)引入相关理论模型,如有限元法的应用,构建木材多尺度结构的自由缩胀可视化有限元模型。

Shrinkage and swelling of wood are critical characteristics that impact its processing and utilization.This is closely link to the dimensions and stability of wood products.The complexities of shrinkage and swelling are closely correlated with the multi-scale hierarchical structure of wood,varying from macro-to micro-scales.The shrinkage and swelling behavior of wood is investigated across macro-,meso-,and micro-scales to establish an organic relationship between them.This contributes significantly to a better understanding of the occurrence and evolution mechanism and has important theoretical and practical implications for in-depth comprehension of wood properties and its rational utilization.In this paper,the wood shrinkage/swelling behavior and its hysteresis phenomena under macroscopic scale(clear wood sample),mesoscopic scale(growth ring)and microscopic scale(wood cells)were reviewed.This paper summarized the occurrence and evolution of the shrinkage and swelling behavior of wood at three scales,as well as the test methods and technical means employed to measure these phenomena in wood with multi-scale structures.Meanwhile,some suggestions for future research about the shrinkage and swelling behavior of wood with multi-scale structures are proposed:1)To conduct a systematic investigation into the shrinkage and swelling behavior of softwood and hardwood at the meso-and micro-scales,utilizing growth rings and wood cells,in order to establish the structure-activity relationship between multi-scale structures and their shrinkage and swelling performance.2)To reveal the differential responsive law and interaction mechanisms of the shrinkage/swelling behavior of wood induced by anisotropy,heterogeneity,and the diversity of cell types.3)To illuminate the time hysteresis and strain hysteresis phenomena of the shrinkage and swelling behavior.4)To introduce the related theoretical models,such as the application of finite element method,with the aims to build a visual element finite of the free shrinkage and swelling of wood with multi-scale structures.