Objective  Bamboo is a kind of typical unidirectional long fiber reinforced composite material. The reinforcement phase is bamboo fiber, and the matrix is parenchyma. At present, there are few researches on the mechanical properties of bamboo parenchyma limited by its geometrical morphology, while its mechanical parameters do play important role in building fine numerical model of bamboo, especially the assignment of matrix attribute.

  Method  In this paper, 7 groups of bamboo parenchyma from different heights of culm were extracted by slicing, the slices with a thickness of 30 μm were used to geometrical morphology of parenchyma cells and the slice with a thickness of 80 μm was used to perform tensile tests. The variations of its geometrical morphology and tensile properties including tensile strength, tensile elastic modulus and failure strain in the height direction of bamboo culm were tested and studied.

  Result  The results showed that in the height direction of bamboo culm, geometrical morphology of bamboo parenchyma had no obvious variation pattern. The average tensile strength, tensile elastic modulus and failure strain of parenchyma were 13.08 MPa, 830.86 MPa and 1.98%, and all the three tensile parameters had no obvious variation pattern in the height direction of bamboo culm. The linear regression analysis results showed that there were low correlationship among parenchyma tensile properties and parenchyma cell geometrical morphology. Tensile failure mechanism of parenchyma was analyzed, and it was found that the tensile failure of parenchyma was the tensile failure of parenchyma cell interface and cell wall, thus the tensile strength of bamboo parenchyma here ranged from 13.08 to 34.82 MPa actually.

  Conclusion  The test method and results are all reliable, which could provide theoretical basis for the further study of mechanical properties of bamboo, especially for the numerical simulation of bamboo. However, deep study should be performed to improve the accuracy of test results, and the relationship between parenchyma mechanical properties and the variation pattern of parenchyma cell organization structure still need to be explored.