Electrical impedance analysis of carbon nanotube/epoxy nanocomposite-based piezoresistive strain sensors under uniaxial cyclic static tensile loading

Abstract

Carbon nanotubes-based nanocomposites have gained a great amount of attraction and play a key role in the realization of strain sensors owing to their remarkable physical properties. In this study, the piezoresistivity of multi-walled carbon nanotubes (MWCNTs)/epoxy-based nanocomposite-based strain sensor under static tensile load is examined using electrochemical impedance spectroscopy. Morphological examinations show that MWCNTs are randomly and homogeneously distributed in the epoxy polymer matrix. A simplified resistance constant phase element model is proposed and validated by impedance spectrum to fit the impedance spectra and the equivalent circuit parameters are extracted under uniaxial static load. Impedance results suggest that depending on the frequency regions, the sensor exhibits different responses under loading. Moreover, the proposed sensor gives high sensitivity, linearity and low hysteresis under cyclic quasi-static loading and unloading that makes the sensor a promising candidate for practical strain sensor applications.

Tuning the piezoresistive strain‐sensing behavior of poly(vinylidene fluoride)–CNT composites: The role of polymer–CNT interface and composite processing technique

“…Development of piezoresistive strain-sensors based on polymer nanocomposites has been intensively researched in recent years due to their potential applications in structural health monitoring, [1][2][3][4][5] energy harvesting, 6 wearable devices, 7,8 flexible electronics, 9 unmanned air vehicles and robotics 10 etc. Moreover, conducting polymer composites (CPC) using high aspect ratio conducting fillers, like carbon nanotubes (CNT) can be prepared and shaped easily by traditional polymer processing methods like casting (in case of thermoset polymer), melt mixing followed by compression or injection molding and solution casting, and the techniques like extrusion and electrospinning.…”

Improving the usability of piezoresistive bond lines in wood by using impedance measurements

“…The four assumptions are the intrinsic electrical resistance of a conductive particle itself (1), the contact resistance of contacting particles (2), the tunneling effect between conductive particles which are not touching (3), and micro-capacitors formed through the Maxwell-Wagner-Sillars polarization in the interfaces between conductive particles (4), if insulating polymer can be found between two conductive particles (Elimat et al 2010;Sanli et al 2016;Sanli and Kanoun 2020;Xia et al 2017). The impedance measured by impedance spectroscopy for a range of frequencies can be written as Z = Z � + iZ �� in the Cartesian form for each frequency, where Z′ is the real part (Re(Z)) and Z″ is the imaginary part (Im(Z)) of the impedance (Elimat et al 2010;Sanli and Kanoun 2020). Compared to the DC-resistance the impedance for alternating current takes phase differences into account and can be carried out for different frequencies (Elimat et al 2010;Sanli and Kanoun 2020) which gives the ability to receive more information on the electrical characteristics of the examined material.…”

“…The impedance measured by impedance spectroscopy for a range of frequencies can be written as Z = Z � + iZ �� in the Cartesian form for each frequency, where Z′ is the real part (Re(Z)) and Z″ is the imaginary part (Im(Z)) of the impedance (Elimat et al 2010;Sanli and Kanoun 2020). Compared to the DC-resistance the impedance for alternating current takes phase differences into account and can be carried out for different frequencies (Elimat et al 2010;Sanli and Kanoun 2020) which gives the ability to receive more information on the electrical characteristics of the examined material.…”

“…The effects (1) to (3) can be measured in the real part of the complex impedance (Xia et al 2017), which describes the dissipation of electrical energy as thermal energy and includes all ohmic parts (Funke 1993). On the contrary, effect (4) can be measured in the imaginary part of the complex impedance (Elimat et al 2010;Sanli et al 2016;Sanli and Kanoun 2020;Xia et al 2017) which describes the amount of electrical energy stored in the material containing induction and capacitance (Funke 1993).…”

“…Impedance spectroscopy can be used to identify optimal frequencies with high signal quality and reliability in electrically conductive bond lines. The described mechanisms react to different applied frequency ranges in the measured signal to a varying extent (Sanli et al 2016;Sanli and Kanoun 2020;Xia et al 2017). Thus, this research study focuses on the piezoresistive response of bonded wood samples at various frequencies under compressive shear load as one of the critical load situations in timber engineering, for example shear load at the end face or inclined cut of curved glulam beams.…”