竹材在压缩大变形下的力学行为Ⅱ.微观变形特征

Mechanical Behavior of Bamboo with Large DeformationⅡ. The Characteristics of Microcosmic Deformation

以毛竹小试件为对象,使用显微加载装置研究了竹材在三个方向的压缩大变形下微观结构的变化特征。研究表明,竹材在径向受压和弦向受压时具有相同的屈服极限,这主要取决于薄壁基本组织在横向具有相同的屈服行为。由于竹材基本组织是传递荷载的优良基体,竹壁在径向压缩和弦向压缩下具有相同的宏观力学行为,可视为两相纤维复合材料;在轴向压缩大变形下,竹材承载的主体是竹纤维,轴压屈服极限是横压屈服极限的3倍。

The relationship between the changes of microstructure and mechanical behavior of Moso Bamboo (Phyllostachys pubescens) with large compressive deformation were determined with a microscope-loading device. Bamboo samples were compressed in three directions: radial, tangential and longitudinal. The results indicated that: 1) under radial and tangential compression, parenchymatous ground tissue was the basic component for transferring loads. It exhibited the same yield performance and, therefore, bore the same yield limit. In the same way, the bamboo wall revealed the same macro mechanical behavior, which showed bamboo could be regarded as a two-dimensional composite material. 2) Under longitudinal compression, the loads were borne by bamboo fibers and, therefore, the yield limit of bamboo with longitudinal compressive deformation is three times higher than that with transverse compressive deformation.