Durability evaluation of madake bamboo by FE analysis of fracture with consideration of fibre direction

Abstract

The flexural stiffness of bamboo is inherently influenced by heterogeneous material characteristic owing to its unique hierarchical structure. In addition, low interfacial strength and unequal distribution of fibres lead to a complex fracture behavior in the material. This research study aims to probe into the limited durability of MADAKE bamboo (Phyllostachys bambusoides) by investigating its fracture mechanism through numerical simulation. The influence of functionally graded material (FGM) on the fracture behavior of bamboo culm was evaluated. A half-solid cylindrical model consisting of a rigid section and a 4-layered wall section was simulated in pure bending mode on LS-DYNA. The effects of material homogeneity and inhomogeneity were replicated by inputting elastic and orthotropic-elastic material data comprising of longitudinal to flexural stiffness ratio. These ratios were derived from experimental results of three-point flexural test. Analysis of results, based on maximum principal strain, showed that the homogeneous model displayed fracture characteristics similar to conventional elastic material. In contrast, the inhomogeneous model displayed maximum principal strain on the lateral surface corresponding to fracture mode of bamboo culms observed in nature. Numerical study of material heterogeneity is a step further in understanding the fracture mechanics of functionally graded materials.