Beyond Monofilaments - Twist Inserted NiTi Microfiber Yarns and Textiles with Controllable Performance

In traditional yarn manufacturing, twist is inserted into a bundle of fibers to create an interlocked cohesive structure capable of withstanding rigorous textile manufacturing processes. The process of twist insertion can be used to create multifunctional yarns and textiles through the integration of multifunctional material systems into a new structural form. However, there is little understanding of the role of yarn parameters (yarn count, fiber packing density, twist, structure) on the performance of multifunctional yarns and textiles. Through the implementation of a new combinatorial technique, Fort Wayne Metals can produce NiTi fibers with 3-5μm diameters, which are ideal for spinning into a functionalized yarn. This research demonstrates traditional shape memory and superelastic behavior in twist inserted NiTi microfiber yarn structures and highlights the increased performance tailorability and manufacturability achieved as a result of an understanding of the role that yarn parameters play within a multifunctional structure. A streamlined NiTi microfiber material, yarn, and textile manufacturing and processing procedure will be outlined. We will then experimentally demonstrate the impact of manufacturing and processing parameters on NiTi yarn performance. Experimental results will be analyzed from an understanding of material strains within a yarn structure. We will discuss modifications to traditional yarn models required to capture the performance deviations observed by NiTi yarns. This work presents a next-generation form of NiTi and identifies the performance tradeoffs associated with manufacturing and processing parameters for a crucial intermediate step towards a fully realized NiTi textile.