Piezoresistive Hybrid Nanocomposites for Strain and Damage Sensing: Experimental and Numerical Analysis

Carbon nanomaterials such as carbon nanotubes (CNTs) and graphite nanoplatelets (GNPs) demonstrate remarkable electrical and mechanical properties, which suggest promising structural and functional applications as fillers for polymer nanocomposites. The piezoresistive behavior of these nanocomposites makes them ideal for sensing applications. Besides, hybrid nanocomposites with multiple fillers like carbon nanotubes (CNTs) and graphite nanoplatelets (GNPs) are known to exhibit improved electrical and mechanical performance when compared to mono-filler composites. To comprehensively understand the mechanisms of electrical percolation, conductivity, and piezoresistivity in hybrid nanocomposites, the author develops a two-dimensional (2D) and a three-dimensional (3D) computational Monte Carlo percolation network models for hybrid nanocomposites with CNT and GNP fillers. In the experimental studies correlated to the computational models, the author fabricates the hybrid nanocomposites made of both fillers using resin infiltration techniques and show an improvement of their electromechanical performance when compared to CNT nanocomposites. Due to the limitations of the resin infiltration techniques, the author develops an inkjet printing procedure with a new water-based CNT ink to fabricated printed nanocomposites on both polyimide film (Kapton) and paper with high device-todevice reproducibility. The ink formulation, as well as the substrate surface treatment, have been optimized to obtain conductive and piezoresistive devices. The author shows the effectiveness of the printed devices as strain sensors and impact damage sensors respectively under mechanical strains and hypervelocity impact damages. Devices printed with the minimum number of ink deposited layers lead to the best sensing performance