The effect of interface shock viscosity on the strain rate induced temperature rise in an energetic material analyzed using the cohesive finite element method

Abstract

In this work, shock induced failure and local temperature rise behavior of a hydroxyl-terminated polybutadiene (HTPB)—ammonium perchlorate (AP) energetic material is modeled using the cohesive finite element method (CFEM). Thermomechanical properties used in the model were obtained from four different experiments: (1) dynamic impact experimental measurements for fitting a viscoplastic constitutive model, (2) in situ mechanical Raman spectroscopy (MRS) measurements of the separation properties for fitting a cohesive zone model, (3) a pulse laser induced particle impact experiment combined with the MRS for measurement of the interface shock viscosity, and (4) Raman thermometry experiments for measurement of HTPB, AP, and HTPB-AP interface thermal conductivity. HTPB-AP interface regions with high density of particles were found to be more susceptible to local temperature rise due to the presence of viscoplastic dissipation as well as frictional heating. The increase in the interface shock viscosity lead to a decrease in both the viscoplastic and frictional dissipation. This resulted in a decrease in the maximum temperature and the density of local regions with a maximum temperature rise within the HTPB-AP microstructure. A power law relation for the decrease in viscoplastic energy dissipation, temperature rise and the density of the local temperature rise with the interface shock viscosity was obtained.

Simulation guided experimental interface shock viscosity measurement in an energetic material

“…This time step was considered in order to approximate the time in which the longitudinal wave traverses the smallest bulk element in at least ten steps, as has been used in shock wave modeling by other researchers [57,58]. In order to explicitly resolve the fracture path inside of the bulk material, as well as at the interfaces, all of the element boundaries were considered to be cohesive surfaces [52,59]. The cross-triangle elements were used in the mesh which enabled the model to be flexible for resolving crack pattern, as well as to reduce the possibility of element locking, figure 1(a) [53,60].…”

Data science assisted cohesive finite element modelling of impact behaviour of AP‐HTPB crystal binder composite

“…Energetic composite materials, used in propellants, fuels and pyrotechnics, are typically composed of crystals of high chemical energy and a binder that agglomerates the crystals into a packed, solid shape. [1][2][3][4][5][6][7][8] Ammonium perchlorate (AP), a white solid inorganic compound, is a strong oxidizer, has high thermal stability and produces low weight fraction of solids in combustion gases. [9] Hydroxyl-terminated polybutadiene (HTPB), a liquid prepolymer, has a high solid loading capacity, great mechanical and ageing properties.…”

“…[10] The microstructure of such materials presents complex mechanical interactions under impact loading, which leads to conditions that can lead to detonation. [1][2][3][4][5][6][7] To understand how detonation happens and establish measures to avoid inadvertent detonation, it is vital to examine the circumstances leading to failure in these solid rocket fuels. Under impact loading, the possible reasons for failure may include the local strain rate, temperature and the presence of pre-existing pores and cracks.…”

Thermo-mechanical behavior measurement of polymer-bonded sugar under shock compression using in-situ time-resolved Raman spectroscopy

“…Conversely, experiments under shock conditions have provided insights into temperature rise due to gas compression 4 , 19 and void collapse 17 , 21 . Interparticle friction 15 , 16 , 24 , 28 , 29 and viscous heating 26 , 30 , 31 effects have been addressed under weak shock conditions. However, the contribution from friction and plastic deformation in microscale domains at shock conditions has not been explored due to the lack of an ability to simultaneously measure stress and temperature under shock conditions.…”

“…For a crystalline such as HMX, shear banding due to large velocity gradients is observed as a possible reason for shock viscosity 22 , 23 . The fracture mechanics of the interface also affects the overall shock viscosity during shock wave rise 7 , 26 , 37 . Shear-thinning has been observed in many metals and granular materials with increasing strain rates 38 .…”