Tensile Properties and Reliability of a Ramie Spun Yarn/ PP Composite Strand

摘要

Recently, natural fiber spun yarns have been anticipated for use as reinforcement of composite materials because natural fibers are environmentally friendly. The form of the spun yarns is unidirectional, so that more increase in mechanical properties is also expected, as compared to randomly-oriented short natural fibers. A continuous ramie spun yarn/PP composite strand was produced using M-PaRI (multi-pin assisted resin impregnation) process, a long fiber pellet production method proposed in the previous paper. Tensile tests were conducted to measure the strands elastic modulus and tensile strength for different MAPP (maleic anhydride grafted polypropylene) contents. It was confirmed that tensile strength and elastic modulus did not change significantly in different MAPP contents. The results also showed that tensile properties increased with increasing fiber volume fraction. In addition, it was confirmed that the variation in fiber orientation angle at the yarn surface affected the C.V. (coefficient of variation) of elastic modulus, and furthermore, comparison among conventional theoretical models and experimental data implied that the angle had a large variation even in the inner layers of the yarn. It is expected that variations in elastic modulus can be decreased by decreasing the coefficient of variation of fiber orientation angles in a spun yarn.