Computational micromechanics analysis of electron hopping and interfacial damage induced piezoresistive response in carbon nanotube-polymer nanocomposites

Abstract

Carbon nanotube (CNT)-polymer nanocomposites have been observed to exhibit an effective macroscale piezoresistive response, i.e., change in macroscale resistivity when subjected to applied deformation. The macroscale piezoresistive response of CNT-polymer nanocomposites leads to deformation/strain sensing capabilities. It is believed that the nanoscale phenomenon of electron hopping is the major driving force behind the observed macroscale piezoresistivity of such nanocomposites. Additionally, CNT-polymer nanocomposites provide damage sensing capabilities because of local changes in electron hopping pathways at the nanoscale because of initiation/evolution of damage. The primary focus of the current work is to explore the effect of interfacial separation and damage at the nanoscale CNT-polymer interface on the effective macroscale piezoresistive response. Interfacial separation and damage are allowed to evolve at the CNT-polymer interface through coupled electromechanical cohesive zones, within a finite element based computational micromechanics framework, resulting in electron hopping based current density across the separated CNT-polymer interface. The macroscale effective material properties and gauge factors are evaluated using micromechanics techniques based on electrostatic energy equivalence. The impact of the electron hopping mechanism, nanoscale interface separation and damage evolution on the effective nanocomposite electrostatic and piezoresistive response is studied in comparison with the perfectly bonded interface. The effective electrostatic/piezoresistive response for the perfectly bonded interface is obtained based on a computational micromechanics model developed in the authors' earlier work. It is observed that the macroscale effective gauge factors are highly sensitive to strain induced formation/ disruption of electron hopping pathways, interface separation and the initiation/evolution of interfacial damage.

Effect of external loads on damage detection of rubber‐toughened nanocomposites using carbon nanotubes sensory network

“…Although a monotonic decrease in electrical resistance up to 45% was observed under quasi‐static and high strain rate conditions, a decreasing (up to 60%) and sudden increasing in resistance (up to 1%) was noticed under medium strain rates. Chaurasia et al conducted computational micromechanics modeling to Study the effective macroscale piezoresistivity of carbon nanotube‐polymer nanocomposites for strain and damage sensing. They identified the formation and disruption of the electron hopping pathways is to be one of the dominant mechanisms affecting macroscale effective piezoresistive response.…”

Effective electrical conductivity of carbon nanotube–epoxy nanocomposites

“…The experimental values of the electrical percolation threshold, lower then those calculated according to geometrical continuum percolation theory, 21 can be explained by nanoscale effects such as hopping 6,23–25 or tunneling 25–27 for electron transport, which do not require direct contact between the CNTs. However, the question about the true mechanism of providing such a low percolation threshold is debatable until now.…”

“…It should be noted that the more complex nanoscale CNT–polymer interface was considered in Chaurasia et al., 24 where it was modeled through the coupled electromechanical cohesive zones within a finite element based on computational micromechanics framework. Such modeling allowed the authors to consider such effects as interfacial separation and damage.…”

Enhanced imaging of piezoresistive nanocomposites through the incorporation of nonlocal conductivity changes in electrical impedance tomography

“…Although such models are accurate on the micro-scale, they can be computationally burdensome to implement on the macro-scale. Computational micro-mechanics models use finite element methods to model representative volume elements (RVEs) consisting of nanofillers and the surrounding matrix material (Chaurasia et al, 2014a, 2014b; Ren et al, 2015, 2016). This approach is useful for understanding mechanical effects such as interfacial separation and damage evolution in nanocomposites.…”