Mesoscale strain and damage sensing in nanocomposite bonded energetic materials under low velocity impact with frictional heating via peridynamics

The formation of hotspots within polymer bonded explosives can lead to the thermal decomposition and initiation of energetic materials. A frictional heating model is applied at the mesoscale in this study to assess the potential for the formation of hotspots under low velocity impact loadings. The frictional heating mechanism predominantly depends on the formation and growth of microstructural damage within the energetic material. Monitoring of the formation and growth of damage at the mesoscale is considered through the inclusion of piezoresistive carbon nanotube network within the energetic binder providing embedded strain and damage sensing. A coupled multiphysics thermo-electro-mechanical peridynamics framework is developed to perform computational simulations on an energetic material microstructure subject to low velocity impact loads. The coupled framework allows for the assessment of traveling compressive waves caused by impact with piezoresistive sensing, growth of damage with damage sensing and the possible formation of hotspots. The sensing mechanism has been shown to capture the presence of the compressive mechanical wave at different locations within the microstructure before large damage growth. It is observed that the development of hotspots is highly dependent on the impact energy. Higher impact energy leads to larger amounts of microstructural damage providing more damaged surfaces for friction to take place. The higher impact energy also yields larger relative velocities of sliding damage surfaces resulting in more frictional heating. With increase in impact energy, the model also predicts larger amounts of sensing and damage thereby supporting the use of carbon nanotubes to assess damage growth and subsequent formation of hotspots.