Mechanical properties of a novel tri-component high stiff auxetic reinforced composite structure

Helical Auxetic Yarn (HAY) possesses negative Poisson’s ratio. These yarns can be successfully used as reinforcing elements in composite materials. This paper proposes a novel tri-component helical auxetic structure capable of enhancing the initial modulus of HAY. The novel structure comprises a high modulus thin secondary core II positioned along the first low modulus thick primary core I. An additional stiff strand wraps the cores I and II. Using statistical techniques, evaluation of the secant modulus and not Young’s modulus was carried out and validated. The resultant structure was found to possess a relatively high elastic modulus in the range of 11–15 GPa. The structure exhibited an auxetic phenomenon of −62. It was revealed that such high stiffness auxetic yarn could successfully be utilized as reinforcing elements in high stiffness cost-effective auxetic composite structures.