Effect of yarn structure on mechanical properties of natural fiber twisted yarns and green composites reinforced with the twisted yarn

Abstract

Natural fiber twisted yarn has high potential as a reinforcement of green composites, because the yarn is produced as a continuous form, which is necessary for exhibiting reinforcing mechanism in a composite. In a twisted yarn, spun yarn filaments meander from the twisted yarn surface to inner along the yarn axis. This phenomenon is called -migration-, and yarn structural mechanics has been developed by taking an ideal migration into consideration. In the yarn mechanics, yarn tensile properties are often expressed as a function of twist angle, while yarn structure depends strongly on performance of twisting machine. Thus, the present study deals with the effect of twist contraction ratio (TCR), one of the most important parameters in yarn structure, on tensile properties of twisted yarns and green composite reinforced with twisted yarn. Ramie spun yarn filaments were used as a test material, and the twisted yarn were produced using auto or hand twisting machine. The results show that relation between mechanical properties of the twisted yarn and yarn structure can reasonably be comprehended when choosing TCR as an evaluation parameter. Furthermore, this study additionally deals with relation between theoretical elastic modulus, and twist angle or TCR based on the experimental data of green composites as well as twisted yarns.© 2012 The Society of Materials Science, Japan.