Title: Experimental Characterization and Computational Modeling of Deformation and Damage Sensing Through the Piezoresistive Response of Nanocomposite Bonded Surrogate Energetic Materials

Adarsh K. Chaurasia, Engin C. Sengezer, Krishna K. Talamadupula, Stefan Povolny, Gary D. Seidel,
Dept. of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, 224-13 Randolph Hall (0203) Blacksburg, VA 24061, USA

Journal of Multifunctional Composites -- 2014 -- Vol. 2 No. 4 ISSN 2168-4286 (backdated)

Abstract
The current work aims to explore the potential for in-situ structural health monitoringin polymer bonded energetic materials through the introduction of carbon nanotubes(CNTs) into the binder phase as a means to establish a significant piezoresistive responsethrough the resulting nanocompositebinder. The experimental effort herein isfocused towards electro-mechanical characterization of surrogate materials in placeof actual energetic (explosive) materials in order to provide proof of concept for thestrain and damage sensing. The electrical conductivity and the piezoresistive behaviorof samples containing randomly oriented, well dispersed MWNTs at concentrations of0.09–0.6 %wt introduced into the epoxy binder of 70 %wt granulated sugar-epoxy hybridcomposites are evaluated. In the computational modeling e.ort herein, the effectivepiezoresistive response of these nanocompositebonded polymer explosives (NCBX) isevaluated using a computational micromechanics approach based on a 2-scale hierarchalmodel connecting the CNT-polymer nanocomposite scale (nanoscale) to the explosivegrain structure scale (microscale). Scanning Electron Microscopy (SEM) basedmicrostructuremorphology of as-produced MWNT-sugar-epoxy hybrid composites isused to construct a representative microscale computational domain. The nanocompositebinding medium is modeled as electromechanical cohesive zones betweenadjacent explosive grains which are representative of effectiveelectromechanical responseof CNT-polymer nanocomposites. The effective electromechanical properties ofCNT-polymer nanocomposites are obtained using the Mori-Tanaka method allowing forrandom and aligned orientations of CNTs within the binder. The real time in-situ electricalresistance measurements under quasi-static tensile loading obtained both experimentallyand in computational modeling demonstrate the strain and damage sensingpotential in hybrid composites.

Key words: energetic materials, multiscale, cohesive zone, electromechanical coupling, strain sensing, damage detection