EAGER: Knit One, Purl Two, Studies on the Properties of Knitted Fabrics for Advanced Engineering Applications

This EArly-Concept Grants for Exploratory Research (EAGER) project concerns the study of an ancient and ubiquitous, yet understudied, class of materials: knitted fabrics. The aim is to explore these novel materials, and their unusual elastic properties, using recently developed concepts in theoretical physics together with basic experiments for the establishment of a firm foundation upon which this field of study can grow. Engineers and artisans have developed for millennia methods for weaving yarns into fabrics with desired properties, and nowadays many novel applications are appearing, such as soft actuators, animated toys, artificial muscles, improved roadways, and armament protection, to name a few. Despite the wide range of uses of knitted fabrics, basic and foundational questions remain about their true nature – how their structures give rise to their unusual elastic properties. Answering this question can allow us to design new fabrics that are stronger and more robust than existing materials. Further, it can allow us to design fabrics that transport energy in directed and predictable ways for use in actuators and energy dissipation systems. The study of knitted fabrics is also a perfect vehicle for broadly connecting the wider public with science and engineering as there are many artisans and hobbyists working with knitted materials. To that end the project includes outreach activities to school children and knitting hobby communities. The objective of this project is to establish a theoretical mechanics-based understanding of anomalous elastic phenomena in knitted fabrics using novel methods and ideas from condensed matter physics. Using these approaches, this work also seeks to open the field of topologically protected vibrational edge modes in these materials and to experimentally observe these modes in designs that would be identified theoretically. The approach will focus on the application of knot theory and condensed matter group theory applied to periodic and quasi-periodic structures (including defected systems) to explain the odd elastic properties seen in experiments and to explain the high elasticity seen in these systems despite being composed of high rigidity yarns. In this regard, the effort will also examine the role of chirality and group theory in explaining experimentally seen behaviors. Analogous to Anderson localization in condensed matter physics, the approach will also explore the possibility that disorder in fabrics leads to localization of vibrations, and whether designed disorder can lead to strength enhancements. The gained theoretical understanding and experimental demonstrations are intended to lay the foundation for new and promising applications. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.