Citation: Shah, A.A.; Shahid, M.; Siddiqui, N.A.; Nawab, Y.; Iqbal, M. Effect of Geometric Arrangement on Mechanical Properties of 2D Woven Auxetic Fabrics. Textiles 2022, 2, 606–623. https://doi.org/10.3390/ textiles2040035 Academic Editor: S M Fijul Kabir Received: 22 September 2022 Accepted: 17 November 2022 Published: 21 November 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article Effect of Geometric Arrangement on Mechanical Properties of 2D Woven Auxetic Fabrics Arif Ali Shah 1, *, Muhmmad Shahid 1, * , Naveed Ahmad Siddiqui 2 , Yasir Nawab 3 and Mazhar Iqbal 2 1 School of Chemical and Materials Engineering, National University of Sciences & Technology, Islamabad 44000, Pakistan 2 Centres of Excellence in Science & Applied Technologies (CESAT), Islamabad 44000, Pakistan 3 Dean School of Engineering and Technology (SET), National Textile University, Faisalabad 44000, Pakistan * Correspondence: arifphd.scme@student.nust.edu.pk (A.A.S.); mshahid@scme.nust.edu.pk (M.S.) Abstract: Textiles-fibres, yarns and fabrics are omnipresent in our daily lives, with unique mechanical properties that fit the design specifications for the tasks for which they are designed. The development of yarns and fabrics with negative Poisson’s ratio (NPR) is an area of current research interest due to their potential for use in high performance textiles (e.g., military, sports, etc.). The unique braiding technology of interlacement for preparation of braided helically wrapped yarns with NPR effect with later development of auxetic woven fabric made it possible to avoid the slippage of the wrapped component from the core. The applied geometrical configuration and NPR behaviour of the braided helical yarn structure with seven different angles comprising of monofilament elastomeric polyurethane (PU) core with two wrap materials that include multifilament ultra-high molecular weight polyethylene (UHMWPE) and polyethylene terephthalate (PET) fibres were investigated and analysed. The mechanically stable 2D woven textile auxetic fabrics (AF) with various weave patterns such as 2/2 matt and 3/1 twill were developed from the auxetic yarn with PU elastomer core having maximum NPR effect of −1.70 using lower wrapped angle of 9 ◦ to study and compare their mechanical responses. The auxetic yarn was used in weft direction and multifilament UHMWPE yarn in warp direction, using semi-automatic loom. Auxeticity of AF was analysed and its various mechanical properties such tensile strength, impact energy absorption, in-plane, and out-of-plane auxeticity, and puncture resistance were studied. Higher energy absorption of 84 Nm for matt fabric was seen compared to twill fabric having an energy of 65 Nm. The puncture resistance capability of matt fabric was better than twill fabric. While twill fabric exhibited better auxetic effect in both in-plane and out-of-plane mode compared to matt fabric. In short, both the twill and matt design AF’s showed unique characteristics which are beneficial in making various protective textiles such as protective helmets, bullet proof shields, cut resistance gloves, blast resistant curtains, and puncture tolerant elastomeric composites. Keywords: negative Poisson’s ratio; yarn; woven auxetic fabric; twill; matt; puncture resistance; protective textile 1. Introduction Auxetic materials are compose a new class of materials that behave contrary to the normal materials, which contract in transversal direction when expanded longitudinally [1]. These materials are better described by the Poisson’s ratio having negative values in contrast to normal materials [2]. Auxetic materials are categorized both as natural and synthetic. Auxetic honeycomb (AHC) exhibit best auxetic nature amongst all auxetic geometries [3]. Natural Auxetic materials are human body parts such as bone tissues, tendons, skin [4], cubic crystals, cow skin, and cat teats [5]. Foams, fibres, yarns, fabrics, and composites are classified as synthetic auxetic materials. Auxetic foams have higher load bearing capacities and formability than conventional foams [6]. Therefore, auxetic foams are categorized as Textiles 2022, 2, 606–623. https://doi.org/10.3390/textiles2040035 https://www.mdpi.com/journal/textiles