Topic of Research Seminar: Design and Development of Auxetic Polymeric Textile Composites for Enhanced Impact Resistance
Abstract: Textiles-fibers, yarns and fabrics are ubiquitous 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 with Negative Poisson’s Ratio (NPR) is an area of intense current research interest due to their potential for use in high performance textiles (e.g., military, sports, etc.). A simple method for preparation of braided helically wrapped yarns with NPR effect is described which was subsequently used for development of Auxetic woven fabric. Due to this unique interlacement braiding technology used for development of yarns, the slippage of the wrapped component from the core was avoided. The geometrical and auxetic behaviour of the braided helical structure for two various monofilament core materials including elastomeric Polyurethane (PU) and Polyester cord with similar combination of wrap materials that include multifilament Ultra-High Molecular Weight Polyethylene (UHMWPE) and Polyethylene Terephthalate (PET) fibres and various set of braiding angles were analyzed. Yarns braided at seven different angles were investigated to analyze materials’ behaviour towards NPR of the applied braided configuration. It was observed that the NPR of the Auxetic yarns was dependent upon the selection of the core and wrap materials and the braiding angle. The NPR value was higher for a core with the higher elasticity (e.g., PU elastomer compared with polyester); a lower wrap angle and lower braiding speed also exhibited higher NPR. The maximum NPR value of -1.70 was obtained using a PU core wrapped at an angle of 9°, when tested at a strain rate of 50%. There are two approaches to fabricate auxetic textiles from the auxetic yarns. In the first approach, conventional yarns are knitted or woven in a special geometrical arrangement e.g., plain, twill, satin, and matt design to get the auxetic effects. In the second approach, the auxetic yarns manufactured by various simple processes are used directly to knit or weave the textile fabrics from these yarns. Development of 2D woven Auxetic Fabrics (AF) is a new approach to develop mechanically stable auxetic textile structures. The mechanical response of such woven structure with various weave pattern is studied in detail. Several mechanical properties of Matt and Twill designed 2D woven AF are compared. AF was developed using auxetic yarn (combination of PU elastomer, UHMWPE and PET yarns having lowest angle of 9°) in weft direction and multifilament UHMWPE yarn in warp direction, using semi-automatic loom. Auxeticity of AF was analyzed and its various mechanical properties such tensile strength, impact energy absorption, in-plane, and outof-plane auxeticity, and puncture resistance were studied. Both the twill and matt design AFs showed superior mechanical properties that will be helpful in protective textiles applications like protective helmets, bullet proof shields, cut resistance gloves, blast resistant curtains, and puncture tolerant elastomeric composites.
Laminated composites were developed from these fabrics to observe the auxeticity obtained in composites developed from the two types of fabrics with Linear low-density polyethylene (LLDPE) used as matrix. The auxetic effect on the mechanical properties of the prepared fabric / LLDPE composites was investigated. The mechanical properties include the tensile, flexural and impact properties. All these properties play their role to enhance the auxetic behaviour in the composites.
Subject Field of Topic: Polymeric textile composites
Name of Speaker: Syed Arif Ali Shah Kakakhel
Professorial Rank of Speaker: PhD Scholar
University Email of Speaker: [email protected]
Affiliation of Speaker whether NUST: SCME/ NUST Scholar
Date and Venue: 05 October 2022 at 1200 hrs, Seminar Hall, NUST School of Chemical and Materials Engineering (NUST-SCME)