Characterization of bamboo extrinsic toughening mechanism in bending by X-ray micro-computed tomography(micro-CT)

Bamboo as a natural biomaterial with excellent strength and toughness is widely used in construction, furniture, decoration, handicrafts and other fields. However, the internal cracks that lead to the bending-fracture behavior of bamboo during its application are not yet fully understood. Herein, we used micro-computed tomography (micro-CT) to investigate the external toughening mechanism of bamboo during bending aiming to broaden the application areas of bamboo. These studies demonstrated that bamboo's outstanding strength and toughness were attributed to the synergistic extrinsic toughening mechanism dominated by fibers. Moreover, the fiber delamination and interfacial debonding affected crack deflection in the surrounding parenchyma and vessels. Additionally, the fiber content was positively correlated with the energy release rate of fiber pullout. When the fiber content was close, the fibers closed to the tension side had a better inhibition effect on the crack propagation. Furthermore, the effects of different microstructure arrangements on crack deflection, crack deflection inside fibers, crack deflection in parenchyma, and the toughening mechanism of fiber pullout were also discussed. Therefore, this work further advances the mechanism strategy for enhancing the flexibility of bamboo, which indicates the great potential in bending applications.