Variation In Bamboo Properties Of Bambusa Rigida And Investigation Of Its Ageing Resistance

The bamboo properties and aging resistances of Bambusa rigida were systematically investigated in the present thesis. The variation in culm characteristics, anatomy and physic-mechanical properties were analysed with ages, along culm heights and culm wall thickness zones. Based on the study of internodes’anatomy, physico-mechanical properties, the vatiation of nodes’characteristics were determined along culm height. The ageing resistances of culms were evaluated by using accelerated ageing method. Results of this investigation were as following:The age had a little influence on the culm characteristics, while the culm height had a remarkable effect on those. The internode length of culms was accorded to the regulation of short-long-short along culm height and the culm wall thickness was conformed to second linear fitting relationship. Meanwhile, the internodes diameter decreased according to logarithmic fuction from base to top portion.The vascular bundle size and parenchyma lumen diameter decreased little with ages. The vascular bundle frequency, metaxylem vessel size and parenchyma length reduced along culm height and the longest fiber length was found in the middle portion of culm height. There were significant differences of vascular bundle size, metaxylem vessel size and parenchyma lumen diameter among culm wall thickness zones. In the inner zones, the metaxylem vessel and parenchyma lumen diameter were larger than other zones, and in the middle zones, the fiber length and parenchyma length were relatively longer, and in the ouer zones, there had the thickest fiber cell wall thickness and parenchyma cell wall thickness compared to inner and middle zones. In conclusion, the fiber cell wall thickness and parenchyma cell wall thickness thickened significantly from 1 to 3 years, which was to say that Bambusa rigida was in the stage of maturation during this period.The physico-mechanical properties increased from 1 to 3 years, and then remained relatively steady from 3 to 5 years. The moisture content and shrinkage of culms wall thickness decreased from base to top portion, while the density increased along culm height. Meanwhile, the moisture content reduced from inner zones to outer zones. The compressive strength, shear strength, modulus of rupture and modulus of elasticity of 3-year bamboo culms increased gradually from base to top portion. Since 1-year bamboo culms did not have stable phycio-mechanical properties, and 5-year culms’top portion had a reduction in mechanical properties, the 3-year culm could be harvested for construction purposes.Compared to internode sections, the nodes had lower mechanical properties. From the results, the fiber lumen diameter, vascular bundle frequency, air-dried density, compressive strength, shear strength, modulus of rupture and modulus of elasticity in internode sections were higher than those in the node sections. However, the node sections had higher vascular bundle size (in tangential to radial ratio), metaxylem vessel size, fiber diameter, parenchyma diameter, fiber cell wall thickness, parenchyma cell wall thickness and parenchyma lumen diameter in comparison with internode sections. In addition, the longest fiber length and parenchyma length within one internode were observed in the middle internodes, while those figures for upper internodes were shorter, and that for nodes were shortest.The basic density, volume shrinkage and mechanical properties of aged bamboo culms were lower than that for controls. Furthermore, the base portion of clums was most significantly affected by ageing treatment. The differences in chemical composition provided evidence that the reduction in physical and mechanical properties was related to the loss of low-molecular weight substances and the depolymerization of the carbohydrates cellulose and hemicellulose. Lignin caused the main resistance to the accelerated aging test because the aged specimens had relatively high Klason lignin content. Significant differences (p<0.05) in surface color between the control and aged specimens were observed.