Auxetic metamaterials: A route to auxeticity in textile fibrous structures - potential application on protective apparel

Auxetic fibrous structures represent an innovative class of metamaterials that exhibit a negative Poisson’s ratio, meaning they expand laterally when stretched and contract when compressed. This counterintuitive behaviour, which sets them apart from conventional materials, is achieved through various strategies, of which the use of specially developed auxetic yarns, unique patterns associated with common auxetic geometries, and specific material arrangements can be highlighted. The study of auxetic fibrous structures span a range of applications due to their enhanced mechanical properties, such as increased energy absorption, improved fracture resistance, and superior indentation resistance. This review examines the path of creation of auxetic fibrous structures, from auxetic yarns to knitted and woven designs, as well as reinforced fibrous structures, emphasizing the mechanical principles that drive their auxetic behaviour. Additionally, it explores the potential applications of these structures with special focus on protective garments. By summarizing recent progress and identifying significant challenges and trends, this review aims to provide a detailed understanding of the principles governing the auxetic behaviour of diverse fibrous structures and their relevance to protective apparel.