Unravelling the sensory capability of MWCNT-reinforced nanocomposites: Experimental and numerical investigations

Multifunctional nanocomposite strain sensors, especially those that contain dispersed multiwall carbon nano-tubes (MWCNTs), are known to possess exceptional electrical conductivity. These nano-reinforced composites can be used for structural health monitoring. It is with this in mind that we focus our attention on calibrating the electromechanical behaviour of MWCNT-reinforced epoxy nanocomposites both numerically and experimen-tally. In particular, our main objective is to unravel the coupled electromechanical behaviour of the conducting composite prior to failure. In the numerical effort, we adopted the effective-medium homogenization and Mori-Tanaka method to account for tunnelling resistance and to predict the sensory capability of the newly developed composite. In the experimental effort, a conductive epoxy nanocomposite containing high quality MWCNTs randomly dispersed within liquid neat epoxy system was developed. The conducting domains of the developed nanocomposite were characterized using atomic force microscope (AFM) measurements. Electromechanical characterisation of the MWCNT-reinforced nanocomposites was also performed using controlled uniaxial tensile tests to evaluate its sensory capability against load. The results of our work reveal: (i) excellent agreement with the micromechanical model, and (ii) the dramatic influence of the concentration of the MWCNTs, their agglomeration and aggregation on the sensory sensitivity of the MWCNT-reinforced epoxy nanocomposite. Interestingly, an increase in the MWCNT filler loading led to a decrease in the sensory sensitivity of the nano-composite as measured by uniaxial strain gauge factor. The work was further extended to highlight the sources of errors that could lead to erroneous results in developing and calibrating electrically conducting pathways in polymer nanocomposites.