抄録
The purpose of this study is to improve the strength and stiffness of natural fibers and natural yarn green composites through mechanical treatment, and to compare the mechanical properties of the composites with those of glass fiber composites. Cyclic tensile stress at 50% or 70% level of their initial strengths was applied five or twenty times for single ramie fibers, twenty or a hundred times for ramie yarn green composites. Tensile strength of as-supplied ramie fibers was improved approximately 50% higher than their initial value, for the cyclic stress at their 70% level and the number of cycles at twenty, while mercerized ramie fibers was improved in strength approximately 20% higher than the original value. On the other hand, the mechanical treatment was not so largely affected in strength for ramie yarn green composites, approximately 8% higher than that of the untreated composites, while Young's moduli of cyclic-loaded green composites were significantly improved, i.e. 56% to 67% higher than that of untreated composites. Young's moduli of the improved composites are comparable to the level of usual glass fiber composites.
