In Situ Mechanical Characterization of Structural Bamboo Materials under Flexural Bending

Experimental mechanical characterization of structural biomaterials, coupled with advanced in situ microscopic imaging, is critical for understanding their deformation and failure mechanisms in engineering applications. Our earlier study suggested that bamboo materials, widely used as scaffolding in construction, exhibit superior and asymmetric bending flexural behavior, while their corresponding mechanisms for crack growth under bending are not fully understood due to the complicated hierarchical structure. Here, we developed in situ characterization techniques assisted with high-resolution macro telescope to directly observe the flexural responses of bamboo strips under different loading configurations. Our in situ results show that the hierarchical microstructure of bamboo plays a critical role in alternating the crack propagation behaviors as well as failure mechanisms. In addition, a finite element analysis (FEA) model mimicking bamboo's functional graded (FG) structure has been developed to quantitatively investigate the origins of bamboo's asymmetric characteristics, with a numerical model proposed for crack propagation. Our technique could offer microscopical insights in the flexural failures of structural bamboo materials under bending, which may be of help on the design of advanced FG cellular composites.