Revealing the AC electromechanically coupled effects and stable sensitivity on the dielectric loss in CNT-based nanocomposite sensors

Abstract

This work is concerned with the characterization of load-dependent dielectric loss and sensitivity analysis for CNT-based nanocomposite sensors (CNCSs) under AC loading. To this end, an electromechanically coupled microstructural theory is developed from the bottom up to quantitatively predict their overall dielectric loss change ratio and strain-sensitivity factor. In the theory, various categories of load-dependent functional interface effects, such as strain- and filler-dependent electron hopping and dielectric relaxation, are incorporated into it. The electric damage process under mechanical load is characterized through the principle of irreversible thermodynamics. The outcome is a microstructure-based coupled theory whose predictions of AC dielectric loss change ratio can be directly calibrated with the experimental data of MWCNT/PVDF nanocomposite sensor over a broad strain loading range from 0 to 10% and a wide frequency spectrum from 5 kHz to 500 kHz, where PVDF is a shape memory polymer. The theory further demonstrates the advantage of demarcating CNCSs via the dielectric loss over the traditional electric resistance. It can be used to rapidly determine the macroscopic dielectric loss change ratio by choosing a specific CNT volume concentration and AC working frequency, and further simplify the design procedure of highly sensitive strain sensors.

Keywords

• CNT-based nanocomposite sensors (CNCSs)
• Electromechanically coupled
• AC frequency
• Dielectric loss
• Sensitivity analysis