Piezoresistive detection of simulated hotspots and the effects of low velocity impact at the mesoscale in nanocomposite bonded energetic materials via multiphysics peridynamics modeling

The growth of hotspots within polymer bonded explosives can lead to thermal decomposition and subsequent initiation of the energetic material. An embedded structural health monitoring framework is proposed where carbon nanotubes are embedded within the polymer binder medium of polymer bonded explosives. The presence of the distributed carbon nanotube network enables the detection of hotspots through the analysis of the piezoresistive sensing response. The piezoresistive response correlates changes in the resistivity with changes in the mesoscale strain and damage distribution. The focus of the present study is on the assessment of the detection of hotspots at the mesoscale through analysis of the mesoscale thermo-electro-mechanical response via a multiphysics peridynamics modeling framework. The framework is also applied to assess the combined effects of thermal loading due to the hotspots with inertial effects due to low velocity impact loading. Prescribed hotspots were randomly seeded at various locations within the energetic material and modeled as regions with fast rising temperatures up to and beyond the point of thermal damage initiation. It has been found that the present model is able to detect the presence of hotspot dominated regions within the energetic material through the piezoresistive sensing mechanism. The influence of prescribed hotspots on the thermo-electro-mechanical response of the energetic material under a combination of thermal and inertial loading was observed to dominate the lower velocity impact response via thermal shock damage. In contrast, the higher velocity impact energies demonstrated an inertially dominated damage response, with the transition between the two damage types occurring at an impact energy around 3.75 x 10(5) J/m(3).