Research on the extraction of fluffing characteristic parameters and cluster analysis of heat-treated bamboo bundles based on grayscale image threshold segmentation

Heat-treated bamboo bundles (HB) are essential for producing bamboo scrimber, and their fluffing characteristics significantly affect the final product. However, limited research on quantitatively characterizing the fluffing degree of HB has hindered the performance classification, optimization of bamboo scrimber, and its application in areas such as building structures. This study introduced the grayscale image threshold segmentation to obtain eight morphological parameters and their distribution ranges for 200 HB specimens: average diameter (0.26 ∼ 3.42 mm), average fractal dimension (1.12 ∼ 1.25), connectivity (0.11 ∼ 8.45 pcs/mm²), crack ratio ( T-CR ) (6.56 ∼ 90.41 %), fiber bundle area ( T-FBA ) (19.18 ∼ 328.44 mm²), and maximum area of individual fiber bundle ( T-MIFBA ) (1.42 ∼ 286.84 mm²) on the transverse section, crack ratio ( L-CR ) (1.27 ∼ 83.25 %) and fiber bundle area ( L-FBA ) (558 ∼ 11,366 mm²) on the longitudinal section. A multi-scale image analysis approach was employed to analyze the extracted morphological parameters. Relational clustering analysis indicated that the eight morphological parameters can be categorized into four distinct categories. Qualitative clustering analysis revealed clear hierarchical distributions for average diameter and connectivity but fragmented distributions for L-CR and average fractal dimension . Thus, average diameter and connectivity was found to be effective indicators of HB fluffing degree, while L-CR and average fractal dimension were less suitable. This study achieved the quantitative characterization of HB fluffing degree, thereby establishing a solid foundation for optimizing the fluffing process and facilitating the hierarchical classification and utilization of bamboo scrimber. • Eight morphological parameters of HB were extracted by grayscale threshold segmentation. • Eight morphological parameters can be categorized into four distinct categories. • The average diameter and connectivity reliably quantify HB fluffing degree.