The unique flexibility feature of bamboo: Cantilever-beam loading form the coupling bending-shear effects

Bamboo's remarkable attribute of flexibility has earned it widespread recognition, positioning it as an exemplary material for mimicking biological structures in advanced engineering construction. While the tension, compression, bending, shear, and torsion properties of bamboo have been extensively documented, its response under combined loads remains a topic that warrants comprehensive investigation. Filling this knowledge gap, the present study employs the cantilever-beam principle as a methodological framework to scrutinize the fracture mechanism and mechanical properties of bamboo under the coupling effect of bending-shear. The obtained results reveal a linear decrease in the bending moment from the fixed support to the free end of the strip, while the shear force maintains a constant distribution along the strip's length. Within a specific segment of the strip, the bending stress exhibits a linear increase with the distance from the neutral axis, whereas the shear stress manifests a parabolic variation above or below the neutral axis. During the plastic stage, simultaneous transverse and radial fractures occur, effectively dissipating crack energy through interfacial debonding, fiber sliding, and fiber bridging mechanisms. The presence of stepwise deflection between adjacent internodes allows for substantial overall angular deflection of the bamboo culm without incurring damage. Furthermore, the mechanical properties of the strips demonstrate a positive linear correlation with both the fiber volume fraction and the density of vascular bundles. A notable achievement of this study is the establishment of a numerical structure activity relationship, elucidating the bending-shear coupling performance. This relationship serves to clarify the fracture toughness exhibited by bamboo and provides a valuable reference for performance testing and the formulation of standardized protocols in the realm of biomimetic material production.