3D flexible NiTi-braided elastomer composites for smart structure applications

Abstract

While outstanding functional properties of thin NiTi wires are nowadays well recognized and beneficially utilized in medical NiTi devices, development of 2D/3D wire structures made out of these NiTi wires remains challenging and mostly unexplored. The research is driven by the idea of creating novel 2D/3D smart structures which inherit the functional properties of NiTi wires and actively utilize geometrical deformations within the structure to create new/improved functional properties. Generally, textile technology provides attractive processing methods for manufacturing 2D/3D smart structures made out of NiTi wires. Such structures may be beneficially combined with soft elastomers to create smart deformable composites. Following this route, we carried out experimental work focused on development of 3D flexible NiTi-braided elastomer composites involving their design, laboratory manufacture and thermomechanical testing. We describe the manufacturing technology and structural properties of these composites; and perform thermomechanical tests on the composites, focusing particularly on quasistatic tensile properties, energy absorption, damping and actuation under tensile loading. Functional thermomechanical properties of the composites are discussed with regard to the mechanical properties of the components and architecture of the composites. It is found that the composites indeed inherit all important features of the thermomechanical behavior of NiTi wires but, due to their internal architecture, outperform single NiTi wires in some features such as the magnitude of recoverable strain, superelastic damping capacity and thermally induced actuation strain.

Design and application of ‘J-shaped’ stress–strain behavior in stretchable electronics: a review

“…The sample cut at 90° direction has the lowest initial stiffness and largest transition strain between low and high stiffness, followed by the 45° and 0° directions. For 3D textile fabrics, braiding (Figure 1f, right) is a widely used method, which forms the textile by inter-plaiting yarns along three orthogonal directions, also with capabilities in offering ‘J-shaped’ stress–strain behavior 138 . Figure 7c shows stress-strain responses and optical images of a fabric integrated with electronics under stretching 139 .…”

PEDOT:PSS-Based Conductive Textiles and Their Applications

“…Examples include fabrics that change their color with changes in temperature and fabrics that regulate garments' surface temperature to achieve physiological comfort. Smart materials can be incorporated into the textile structure by different technologies such as embroidering [1], non-woven textile [2], knitting [3], weaving [4], braiding [5], yarn spinning [6], fiber spinning [7], polymerizing [8], coating [9], plating [10] and printing [11].…”

Development of Active-Cells for Macroscopically Deformable Structures

“…More recent work more closely related to our approach has been the encasing of a Nitinol braid into a tube or solid sphere [14] and the creation of a cellular material where the pressure in each chamber affects the bulk material properties [15]. Our previous work considers the packing of cells for connectivity [16,17], neglecting any specific cell design, and our other work presented previously at this conference uses a similar approach of considering "cells of materials" for conductive pathways [18].…”