The mechanical response of a PBX and binder: combining results across the strain-rate and frequency domains

Abstract

Abstract. The mechanical response of a polymer bonded explosive has been measured using a Split Hopkinson Pressure Bar at a strain-rate of 2000 s -1 , across a range of temperatures from 173 to 333 K, with the aim of observing its behaviour in the glassy regime. The yield stresses increased monotonically with decreasing temperature and no plateau was found. The failure mechanism was found to transition from shear-banding with crystal debonding fracture to brittle failure with some evidence of crystal fracture. Similar experiments were performed on samples of its nitrocellulose-based binder material, at a strain-rate of 3000 s -1 across a temperature range of 173-273 K. The failure stresses of the binder approach that of the composite at temperatures near -70°C. The elastic moduli were estimated from post-equilibrium regions of the stress-strain curves, and compared to those obtained for the composite using 5 MHz ultrasonic soundspeed measurement, and powder DMA measurements and quasi-static behaviour reported in a previous paper. The moduli were plotted on a common frequency axis: a temperature-shift was applied to collapse the curves, which agreed with the Cox Merz rule.

Experimentally Simulating High Rate Composite Deformation in Tension and Compression: Polymer Bonded Explosive Simulant

“…In conclusion, the PBS in this study, due to the much more rubbery HTPB binder, is more rubbery than a PBS with 66 %, significantly less, crystalline filler material. Regardless of the differences seen in the HTPB binder used in this study, the overall behavior of transitions broadening as a result of the added explosive or simulant, is consistent with observations in literature [3,21].…”

“…Over the past 15 years, a wide range of investigations of the mechanical properties of polymer bonded explosives (PBXs), and their simulants (PBSs), under high rate deformation have been seen in literature [3,[16][17][18][19][20][21][22][23][24][25], often using Brazilian testing to study tensile behavior (e.g. [26,27]).…”

Strain-rate master curves for a PBX and binder

“…Full methodology and results are given in [8]. Briefly, disc specimens of the UK PBX were compressed at 2000 s -1 in an Inconel steel Hopkinson bar system, with annealed copper pulseshapers used to render smooth loading pulses.…”

“…Williamson's data did not probe this region. In a follow-up study by Drodge and colleagues, this region was explored by combining low-temperature and Hopkinson bar strain-rate [8].…”

Temperature and strain rate effects on the mechanical properties of a polymer-bonded explosive

“…[12][13][14][15][16][17][18][19][20][21][22][23][24]. The main conclusions of such research were: (i) the strain rate and temperature response are generally governed by the properties of the polymer binder [15,16]; (ii) the absolute value of the stress supported for a given strain rate and temperature is governed by the size of the explosive crystals [12,14]. Williamson et al quantified the relationship between strain rate and temperature for a particular PBX through a very detailed study in both monotonic and oscillatory loading [15].…”