Comparative Study of Water Absorption and Dimensional Stability Between Bamboo Nodes and Internodes

Bamboo often suffers from moisture-induced cracking, in which the structural and dimensional differences between nodes and internodes may be key contributing factors. Taking Phyllostachys edulis (Carrière) J. Houz. as an example, this study systematically examined the water absorption behavior and dimensional stability of bamboo nodes and internodes, and further analyzed their pore structure and chemical composition to provide a comprehensive understanding of their moisture response. This study systematically compared nodes and internodes of Phyllostachys edulis in water absorption behavior, dimensional stability, pore architecture, and vascular structure. Results showed that internodes exhibited higher water absorption rates and capacities in both short- and long-term tests, whereas nodes displayed lower water uptake and were prone to cracking during drying, indicating reduced dimensional stability. Anatomical and infrared analyses revealed that diaphragms, transverse vascular bundles, and spiral networks in nodes increased fluid path tortuosity, reducing longitudinal permeability. Pore structure analysis further indicated that internodes contained abundant pores facilitating rapid liquid transport, while node pores were mainly medium to large, favoring liquid retention but limiting permeability. Higher cellulose crystallinity and lignin content in nodes enhanced hydrophobicity, further restricting water penetration. Additionally, the complex fiber orientation in nodes induced anisotropic swelling and internal stress, increasing the risk of twisting and cracking. This multi-scale investigation elucidates the structural and compositional mechanisms underlying the observed differences in water absorption behavior and dimensional stability between nodes and internodes. These findings offer valuable insights for improving the moisture resistance, dimensional stability, and overall performance of bamboo materials in engineered applications, and provide a solid foundation for their targeted modification and optimization.