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In situ detection of the fracture behaviour of moso bamboo (Phyllostachys pubescens) by scanning electron microscopy

Abstract The remarkable fracture toughness of bamboo culms is highly attributed to the proper embedding of the stiff fibre caps of the vascular bundles into the soft parenchyma matrix. In this study, the fracture behaviour of small specimens of moso bamboo (Phyllostachys pubescens) in tension and bending were investigated in situ with a scanning electron microscope (SEM) to visualise crack initiation and propagation within bamboo tissues and its interactions with the structural components (fibres and parenchyma tissues). Fracture surfaces were studied by field-emission SEM. The fracture of bamboo in either tension or bending was non-catastrophic, and cracks propagated in a tortuous manner with massive interfacial delamination. The stiff fibre bundles played an important role in restraining crack propagation, acting as bridges to inhibit cracks opening and also as “crack stoppers” inducing extensive crack-deflections. Microstructural analysis of the fractured surfaces revealed that substantial interfacial debonding, sliding and fibre pull-outs occurred at various length scales, which are believed to be effective in dissipating the crack energy. The synergistic effects of crack-deflection, crack-bridging and interfacial debonding are regarded to be mainly responsible for the remarkable fracture toughness of bamboo.