Influence of cellulose content, lignin content, and fiber breakage on the tensile strength of fiber bundles extracted for different bamboo stem regions

• Lignin content increases significantly in the top section above 7.5 m. • Increased lignin content correlates with reduced tensile strength in bamboo bundle. • The middle section of bamboo stem is ideal for composite reinforcement application. • The base section has inferior mechanical properties than the middle section. The objective of this study is to examine the relationship between lignin content, cellulose content, fiber breakage, and the tensile strength of bamboo fiber bundles across different regions of the bamboo stem according to height. Mature bamboo culms (3–4 years old, Dendrocalamus sp. , at least 7.5 m tall) from northern Thailand were divided into six sections of 1.5 m each, including shoots and leaves, resulting in eight parts in total. Each section was hand-cut into smaller pieces and oven-dried at 105°C overnight. One portion of the samples was ground into powder to determine lignin, cellulose, and broken fiber contents, while another portion was processed into fiber bundles for tensile strength testing in accordance with ASTM 3379. The results indicate that the tensile strength of bamboo fiber bundles is influenced by lignin content, cellulose content, and fiber breakage. Along the stem, lignin content increases with height, whereas cellulose content decreases. The highest tensile strength is observed in the middle regions of the bamboo stem, where lignin content is not at its maximum, but the proportion of broken fibers is relatively low. Therefore, the middle portion of the bamboo stem is the most suitable source of fibers as reinforcement applications in composite materials.