Time-Dependent Effects on the Coupled Mechanical-Electrical Response of Carbon Nanotube Yarns under Tensile Loading

Jude Anike,Angeline Bajar,Jandro Abot

doi:10.3390/c2010003

Jude Anike, Angeline Bajar + Show 1 more

Open Access

https://doi.org/10.3390/c2010003

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Abstract

Carbon nanotube yarns have extraordinary mechanical, electrical and thermal properties that make them attractive for high-performance and multifunctional composite materials. They also exhibit a unique piezoresistive response when subjected to mechanical strain. This characteristic is of interest for sensing applications including strain measurement and damage detection when integrated in polymeric and composite materials. Thus, there is a need to understand the coupled mechanical and electrical behavior of the carbon nanotube yarns to fully comprehend the entire scope of their sensing applications. Of particular interest are their characteristics when used as piezoresistive strain sensors in structures that are subjected to dynamic loading including fatigue and impact, or quasi-static cyclic loading. This paper presents a study about the presence of hysteresis and other time-dependent effects in carbon nanotube yarns during quasi-static cyclic uniaxial tensile loading. By simultaneously measuring the resistance, the load and the displacement histories, any direct correlations between the mechanical and electrical characteristics of the carbon nanotube yarns are investigated including the effect of strain level, strain rate, and stress relaxation. It was observed that all these effects play a significant role in the piezoresistive response of the carbon nanotube yarns. In particular, a low strain rate appears to bring out a unique piezoresistive response that is not observed at higher strain rates. The underlying phenomena determining the piezoresistive responses are hypothesized and discussed in the context of strain rate and maximum strain level.

Highlights

Carbon nanotubes (CNTs) exhibit mechanical and electrical properties that render them inherently multifunctional [1,2]
Studies of CNT yarns have shown that upon the application of mechanical strain, their resistance changes. This phenomenon is known as piezoresistivity and can be tailored to achieve automated structural health monitoring (SHM) in composite materials as CNT yarns can be used as a mechanism for sensing and actuation in real-time [3,4,5,6]
Five CNTreaches yarn its and unloads sample until no load is the applied the was crosshead samples were tested at a low strain level, 0.1%, seven at an intermediate strain level, 0.5%, and original position

Summary

Introduction

Carbon nanotubes (CNTs) exhibit mechanical and electrical properties that render them inherently multifunctional [1,2]. Studies of CNT yarns have shown that upon the application of mechanical strain, their resistance changes. This phenomenon is known as piezoresistivity and can be tailored to achieve automated structural health monitoring (SHM) in composite materials as CNT yarns can be used as a mechanism for sensing and actuation in real-time [3,4,5,6]. The size of the individual CNTs and the wire-like assemblies of axially aligned CNT yarns make them easy to integrate and widely distribute into composite materials for damage detection and strain measurement. Before the CNT assemblies may be used on a large scale, their thermomechanical and electrical responses need to be studied under varying conditions and states including their performance at the subscale.

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