科研之友
微信
新浪微博
Facebook
分享链接
摘要
Bamboo is one of the fastest growing plants and it is abundantly growing in most of the tropical regions. It is considered as a composite material because its structure is composed of long and aligned cellulose fibers embedded in a lignin matrix. Moreover, the bamboo culm shows a composite type of structure on both of the macroscopic and microscopic levels. Additionally, bamboo properties vary significantly along the culm length and culm wall thickness. According to these characteristics, the bamboo culm is a functionally graded natural composite material.
This paper deals with the characterization of the micro-structure of bamboo culms (Dendrocalamus asper) by Digital Image Analysis. The variation of the fiber volume fraction and microstructure across transversal section of the bamboo culm were studied. Furthermore, bamboo properties which influence the specific gravity and bending strength were analyzed along the culm length.
The results show that bamboo culms in transverse section composed of numerous fibers embedded in the parenchymatous ground tissue. The distribution of fiber shows a specific pattern within the culm, both horizontally and vertically. The parenchyma and conducting cells are more frequent in the inner one-third of the wall, while the percentage of fiber is higher in the outer part of the wall. In vertical direction, the fiber area percentage increases from bottom to top with the decreasing parenchyma content. The number of vascular bundles is high and the vascular bundles are dense in the outer part compared to the inner part. The vascular bundles near inner part are almost circular while they are more of elliptical shape near, the outer part of the culm wall. The specific gravity of D. asper rangs from 0.58 to 0.71 while Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) range from 132 to 181 MPa and from 9,465 to 15,115 MPa, respectively. These values are increasing from the bottom to the top of the culm. The results indicated a correlation between microstructure and properties of bamboo material. The specific gravity and bending strength increase linearly with the volume fraction of fiber.
From the microscopic point of view, bamboo is a functionally gradient material with a hierarchical structure. The decrease of fiber volume fraction from the outer to the inner part of the culm wall changes density and properties which have to be considered for bamboo. Moreover, the volume fraction of fiber increases from the bottom to the top of the culm. Subsequently, bamboo can distribute and resist the bending stress generated by wind load. These characteristics make bamboo a good substitute for raw material in construction if the variation of properties is considered in design of products. Bamboo being the fastest growing plant on earth opens a good opportunity for environmental friendly and sustainable resource supply.
- 出版日期2015
