Diameter-Dependent Mechanical Behavior of Typha Natural Fibers: Morphological, Chemical, Thermal, and Statistical Insights

Natural lignocellulosic fibers are potential reinforcements for lightweight polymer composites, but their geometrical heterogeneity complicates mechanical characterization and material selection. This study investigated the influence of fiber diameter on the tensile behavior of commercial Typha fibers through integrated geometrical, morphological, chemical, thermal, mechanical, and statistical analyses. The fibers exhibited an apparent geometrical density of approximately 0.71 g/cm3, a moisture-related mass loss of 10.62%, and a main thermal degradation onset at 278.61 °C. Tensile properties varied markedly among diameter classes: mean tensile strength decreased from 438.85 MPa for fibers measuring 0.06–0.16 mm to 37.31 MPa for fibers measuring 0.50–0.80 mm, while Young’s modulus decreased from 7.49 to 1.43 GPa. An empirical power-law model described the relationship between class-averaged tensile strength and diameter (R2 = 0.983). Weibull moduli ranged from 2.71 to 8.30 within individual diameter classes but decreased to 1.25 when the classes were pooled. These findings indicate that combining dimensionally distinct fiber populations can substantially broaden the apparent strength distribution. Although the influence of cross-sectional geometry and intrinsic structural variability could not be separated, the results demonstrate the importance of diameter-aware characterization for reliable mechanical-property reporting and preliminary reinforcement selection. Further composite-level investigations are required to establish the practical implications of these findings.