基于纳米压痕技术的棉秆微观力学性能分析

Analysis on Micro Mechanical Properties of Cotton Stalk Using Nanoindentation Technique

棉秆具有特殊分子力学现象的生物质材料,其内部微观结构与宏观力学性能息息相关,基于细胞壁水平的微观力学性能研究是探索棉秆复杂力学行为的重要途径。通过显微技术展现了棉秆多尺度、多孔、阶梯状结构特征,表明皮部、木质部和髓部体积比大致比例为23:45:32,其主体是木质部。基于纳米压痕技术分析了沿棉秆横切面径向方向的硬度、弹性模量的变化,结果表明皮部的弹性模量是木质部2倍以上、纳米硬度则小于2倍。该研究结果为棉秆粉碎机械、收获机械及采棉机关键部件的结构设计、材料选择及磨损提供理论基础。

Cotton stalk is biomass composite material with special molecular mechanics phenomenon,and the macro mechanical prop⁃erties is closely related to its internal microstructure.Nanoindentation technique is an important way to explore the complex mechanical behavior of cotton stalk based on experimental observation and characterization.In this study,the complex structures of cotton stalk with multi-scale,multiaperture and ladder-shaped were analyzed on SEM and laser confocal microscope.It is found that the volume ra⁃tio of phloem,xylem and pith is about 23:45:32,andthe hardness and elastic modulus of cotton stalk along the radial direction of a cross section was measured with the nanoindenter.The results showed that the elastic modulus of the phloem is more than 2 times to that of the xylem,but the nanohardness is less than 2 times.The results of the study provide theoretical basis to the structure design,material selection and wear mechanism of key components for crushing machinery,harvesting machinery of cotton stalk.