Quantitative Relationship Between Microstructure and Mechanical Properties of Taro Stem: Spatial Heterogeneity Revealed by Image Analysis

Taro (Colocasia esculenta) stems are promising bio-based feedstocks for composite materials, textile fibres and adsorbents; however, a quantitative understanding of how their microstructure governs mechanical behaviour remains lacking, constraining their application. This study conducted mechanical tests and scanning electron microscopy (SEM) tests on stems harvested from different ground elevations. The results show that axial tensile strength (σt) and nominal radial compressive stress (σc) increase first and then decrease with height above ground. σt (2.67 MPa) and σc (7.64 MPa) both peak at 50–100 mm above ground level. Furthermore, the ultimate nominal compressive strength (σc) is significantly higher than the ultimate tensile strength (σt) at all heights above ground. Correlation analysis revealed that cross-sectional area Ac (r = 0.83), fibre bundle area fraction Pc (r = 0.78) and fibre wall thickness Tc (r = 0.77) were significantly positively correlated with σt, while Ac (r = 0.62) and Tc (r = 0.70) were positively correlated with σc. The tensile and compressive properties are closely associated with three microstructural parameters: cross-sectional area, fibre bundle area fraction, and fibre wall thickness—whereas fibre cell area shows only weak correlations with all mechanical indicators (r < 0.5) and is not a key regulatory factor. The stem cross-section transitions from crescent at the base to near-circular at the apex, with the reduction in bearing area underlying the decline in mechanical properties. These results offer a fundamental basis for tailoring mechanical preprocessing parameters and for selective utilisation of stem segments with distinct mechanical performance, thereby supporting the efficient conversion of this abundant biomass into value added materials.