抄録
The purpose of this study is to confirm a rotation phenomenon around the fiber axis of a kenaf fiber, a representative multi-cell type fiber, during tensile loading, and clarify the rotation mechanism through 3D finite element analysis. The degree of rotation was quantified by measuring rotation angle during the tensile test of a single fiber, by giving a free mechanical condition perpendicular to the tensile direction. Results showed that, although many fiber specimens did not rotate during tensile loading, the rotation was confirmed for approximately one fourth of all the specimens. Young's moduli of the rotation identified specimens are almost the same level as non-rotating fibers, while these fibers indicated a slight decrease in strength, as compared with non-rotating fibers. The coordinates transformation matrix simulating a spatial spiral structure of cellulose microfibrils (CMF) was constructed, and applied for 3D finite element analysis. The calculation results show that rotation occurs in one-cell and seven-cell finite element models, but the magnitude of rotation is much smaller in the seven-cell model. Furthermore, a cell twisted finite element model was carried out to simulate a small-scale disorder in the multi-cell orientation structure, which was observed on the kenaf fiber surface. Finally, it is estimated from the calculation results that rotation occurs only for the fiber in which the mechanical balance between CMF spiral structure and multi-cells' intertwist is not enough.
