Micromorphological and Micromechanical Property Heterogeneity: A Fine-Scale Analysis within a Single Thyrsostachys oliveri Culm

Bamboo fiber is a crucial structural component that significantly contributes to its mechanical properties. T. oliveri possesses excellent physical and mechanical properties and suggesting potential for pulp and paper applications. However, the micromorphology and mechanical properties of T. oliveri fibers remain largely unknown. Therefore, its axial and radial micromechanics and micromorphology must be investigated to enable a more in-depth study. This study was conducted on a single three-year-old culm; therefore, the results primarily describe within-culm spatial variation. In this study, we investigated the morphological characteristics of T. oliveri fibers at various locations of bamboo culm and analyzed their modules of elasticity and hardness using nanoindentation. The results indicated that the fiber morphology of T. oliveri exhibited gradient changes along both the axial and radial directions. Overall, in the investigated culm, T. oliveri fibers showed morphology-based indicators that appear favorable for pulping and papermaking applications. The modulus of elasticity of T. oliveri ranged from 22.1 to 24.0 GPa, while the hardness ranged from 601 to 663 MPa. Specifically, the elastic modulus of T. oliveri was highest in the outer culm wall at the top of the bamboo culm, whereas the hardness was highest in the inner culm wall at the base.