The Role of Microstructure in the Impact Induced Temperature Rise in HTPB-HMX Based Energetic Materials Using the Cohesive Finite Element Method

In this work, impact-induced failure of hydroxyl terminated polybutadiene (HTPB) – Cyclo tetra methylene tetra nitramine (HMX) energetic material samples is studied using the cohesive finite element method (CFEM). The CFEM model incorporates a viscoplastic constitutive model using experimentally measured parameters, interface level separation properties, and temperature increase due to mechanical impact. Nanoscale dynamic impact experiments were used to obtain parameters for a strain-rate dependent viscoplastic constitutive model for HTPB, HMX, and the HTPB-HMX interfaces. Mechanical Raman spectroscopy (MRS) was used to obtain cohesive zone model parameters to simulate interface separation. Microstructures having circular HMX particles were found to show higher local temperature rise as compared to those with diamond or irregular shaped HMX particles with sharp edges. Regions within the analyzed microstructures near high-volume fraction of HMX particles were found to have relatively high temperature spikes.