Highly Performing Nanocomposite Sensors for Damage Detection

Abstract

Due to their superior physical and electro-mechanical properties, Carbon Nanotubes (CNTs) are one of the most promising composite fillers to realize ultralight and flexible strain sensors that can be used, among others, to monitor strain concentrations within a structure when damage occurs. In this study, sensors are made of Multi-walled Carbon Nanotubes (MWNTs) embedded in a Polymide (PI) matrix. Nanocomposites are characterized under no-load conditions to study the electrical properties, and under tensile loading conditions, to evaluate the electromechanical and piezoresistive response. The results highlight a two orders of magnitude decrease in electrical resistivity if compared with previous studies, the capability to instantaneously respond to unpredictable deformations and to easily adapt to three-dimensional shapes. The beauty of the as conceived nanocomposite film, if compared with the commercially available strain gages, is its unprecedented potential expandability to monitor larger areas without the loss of ultra-low local (in scale) detection. Local detection is in fact allowed by nanoscale morphology changes that induce changes in local electrical conduction. The selected polyimide matrix allows the use of the proposed sensor to harsh and high temperature environments while keeping high flexibility and excellent mechanical properties, key parameters for the realization of reliable electromechanical films.