Effects of node with discontinuous hierarchical fibers on the tensile fracture behaviors of natural bamboo

Bamboo is widely planted in the world and many species of bamboo are intensively used as sustainable bio-composite materials in the construction of houses, pavilions, furniture and bridges, etc. The bamboo nodes play an important role on natural bamboo's strength. This paper is focused on the structure-property-fracture relations of the natural Moso bamboo with node. The inner structures are characterized by optical and scanning electron microscopy (SEM), which indicated that bamboo node has coarser fiber bundles, higher volumes of fibers and 3D woven hierarchical fibrous structures. Though the fibers on the out and inner skins of node are discontinuous, it has higher strength than internodes samples. There are three kinds of fracture behaviors within bamboo node during the tensile fracture process as detected by acoustic emission (AE), which are matrix (parenchyma cells) failure, fiber dissociation and fiber breakage. The AE results indicated bamboo node has much lower volumes of fracture behaviors, higher proportions of fiber dissociation and matrix failure due to its hierarchical fibrous woven structure. The strengthening effects within bamboo node are concluded as coarse fiber bundles, high volumes of fibers, fiber pull-out and crack deflections.