Anisotropic tensile performance of bamboo parenchyma tissue and its influencing factors

The anisotropic mechanical properties of bamboo significantly affected its processing and wide utilization. It was reasonable to speculate that bamboo anisotropic mechanical performance could be related to parenchyma cells, due to parenchyma cells’ considerable volume fraction and different fracture modes when bamboo was subjected to different directions loads. However, few studies had investigated the anisotropic mechanical properties of parenchyma tissue and their effects on bamboo anisotropy, due to the difficulty to prepare parenchyma tissue samples in different directions. This paper investigated the mechanical properties of parenchyma tissue in three typical directions, namely, longitudinal, radial, and tangential directions, and summarized the tensile fracture behaviors and modes of parenchyma tissue and its influencing factors. The results indicated that the anisotropic tensile performance of parenchyma tissue was reflected in the tensile properties, fracture modes and crack paths. The longitudinal, radial, and tangential tensile strength were 20.92 MPa, 24.22 MPa, and 27.59 MPa, respectively. The transverse, radial and tangential crack were propagated along different interfaces at different crack deflection angles. The microfibrils angle, chemical composition, pits size and distribution density, cell quantity, and cell dislocation degree affected the parenchyma tissue’ anisotropic mechanical properties. Compared to the effect on bamboo strength, the parenchyma tissue’ anisotropic mechanical performance might have a greater effect on the zigzag crack growth path of bamboo failure. This finding could help designing biomimetic materials with high toughness.