Tensile Experiment and Numerical Simulation of Carbon Fiber and Polyvinyl Alcohol Fiber Helical Auxetic Yarns

Based on the negative Poisson’s ratio (NPR) effect obtained from the design of fiber, an auxetic structure of carbon fiber and PVA fiber was designed in this study. Based on the diameter ratio of 1:3, the mechanical behavior and negative Poisson’s ratio (NPR) of fiber helical auxetic yarns (HAYs) with different wrap angles were tested, and the mechanical behavior of fiber HAYs was obtained by digital speckle correlation method (DSCM). It is found that the Poisson’s ratio of HAYs is related to the initial wrap angle, and the maximum value of NPR is −1.35 when the wrap angle is 10°. Based on the test results, the finite element simulation method was used to discuss the mechanical behavior of fiber HAYs with different parameters. The results of the model were basically consistent with the experimental results under the diameter ratio of 1:3, while the maximum value of NPR in the model is −7.03, which appears when the wrap angle is 10° and the diameter ratio is 1:2.