Real Time In-Situ Sensing of Damage Evolution in Carbon Nanotube-Polymer Nanocomposite Bonded Surrogate Energetics

摘要

The current work aims to explore the potential for in-situ structural health monitoring in polymer bonded energetic materials through the introduction of carbon nanotubes (CNTs) into the binder phase as a means to establish a significant piezoresistive response through the resulting nanocomposite binder. The experimental effort herein is focused towards electro-mechanical characterization of surrogate materials in place of actual energetic (explosive) materials in order to provide proof of concept for the strain and damage sensing. The electrical conductivity and the piezoresistive behavior of samples containing randomly oriented, well dispersed MWNTs at concentrations of 0.09-0.6 wt% introduced into the epoxy binder of 70 wt% granulated sugar-epoxy hybrid composites are quantitatively and qualitatively evaluated. Ductile failure behavior going through the initial linear elastic behavior, formation of microcracks leading to reduction in composite stiffness and finally macrocracks result in eventual failure were observed in the mechanical response of MWNT-sugar-epoxy hybrid composites. The real time in-situ relative change in resistance captured the effect of microcracks and macrocracks earlier than the stress strain response resulting in gauge factors between 5-10 before significant macrocrack formation and over 50 at composite failure.