Investigation of twist structure contributing to strength improvement of a ramie twisted yarn

Abstract

Fiber reinforced plastics (FRP) using artificial fibers exhibit excellent strength and stiffness, and therefore have been used in various fields, whereas after use they have brought significant environmental problems such as abandoned scrapped FRP boats. In recent years, as a sustainable FRP, composite materials reinforced by natural fibers, called “green composites” are attracting attention. Thus, in the past we investigated the optimum twist structure of a ramie fiber twisted yarn to improve the composite strength. In this study, we developed a manual twisting machine producing the optimum structure, and evaluated the tensile strength of a twisted yarn green composite consisting of seven inside single yarns and twelve outside single yarns. Twisted yarn specimens were manufactured using the machine with or without a motor that moves a yarn fixing jig. As a result, tensile strength of the twisted yarn was reduced by using the motor, but the strength could be improved by impregnating an epoxy resin. Furthermore, when the yarn was impregnated with ethanol in advance, the orientation angle decreased during twisting and the tensile strength was improved.