Effect of wall thickness and node diaphragms on the buckling behavior of bamboo culm

The buckling behavior of bamboo culm is highly affected by internodal properties, i.e. material properties and geometric parameters of the trunk. In this study, the effects of Phyllostachys Edulis bamboo culms have on buckling phenomena under bending and compressive loads are investigated. Internodal walls are assumed to be composed of orthotropic functionally graded-type materials which are controlled by the volume fraction of the vascular fiber bundle. Provided that the trunk wall thickness near the node is greater than that in the internode and that the number of fibers is mostly unchanged, the internode and node walls are defined by shell elements with the same composite layup material but different thicknesses. It is found that, with a constant internodal length the buckling behavior transitions from global to local as the tube radius increases. The global buckling load increases with approximately a fourth order polynomial in relation with the radius while the local buckling load linearly increases with the tube radius. Nodal wall thickening enhances the buckling load in both the global and local domains. There is an interactive contribution of nodal wall and diaphragm thicknesses on the buckling behavior up to a certain point where the local buckling load is independently determined by each internodal structure. The buckle can occur within thin diaphragms, which results in much lower buckling load compared with the tube without/removed the diaphragms.