Effect of bamboo nodes on crack generation of round bamboo and bamboo-based composites during drying

Cracking of bamboo results in structural failure, safety issues, resources waste, and economy loss. The influence of nodes on the cracking behavior of bamboo still remains unclear. In this study, cracks in bamboo were classified into three types (end cracking, node cracking, and internode cracking), and the node cracking mechanism was clarified. The results revealed that 72%, 77%, and 89% of the cracks in the middle portion of the samples were generated at the node positions for the round bamboo, laminated bamboo lumber, and flattened bamboo board, respectively, indicating that much more cracks were generated in the nodes than in the internodes during drying process. The reason was the greater tangential shrinkage of bamboo nodes. The thickening and deflection of vascular bundles in nodes caused a higher fiber content and substance density, and thus resulted in greater shrinkage. This study confirmed that bamboo node played a dominant role in the crack generation in both bamboo and bamboo-based composites. The results in this study provided fundamental information for understanding the cracking behavior of bamboo and developing anti-cracking techniques for bamboo.