In Situ Observation of Fracture Behavior of Bamboo Culm

The fracture behavior of bamboo culm under three-point bending has been studied using a micromechanical tester in conjunction with an optical microscope which enabled in situ observation of crack initiation and propagation in the microarchitecture of fiber bundles, parenchyma cells, and vascular bundles. Fiber orientation was found to strongly influence the bamboo's fracture behavior. When loading was orientated along fiber bundles, fracture occurred in a brittle manner, whereas when loading was applied perpendicular to fiber bundles, cracks propagated in a trans-parenchyma cell manner accompanied by crack bridging and fiber pulling-out. The cracks preferred to propagate in the fashion of trans-parenchyma cells and inter-fibers. The findings inform future simulation and modeling with correct boundary conditions and parameters, and provide additional design guidelines for developing high-performance bamboo-like composites.