The compressive strength of the energetic composition EDC37 has been measured at a temperature of 293 ± 2 K over a range of strain rates from 10−8 to 103 s−1, and at a strain rate of 10−3 s−1 over a range of temperatures from 208 to 333 K. The results show that failure stress is a monotonic function of applied strain rate or temperature, which is dominated by the relaxation properties of the polymeric binder; this is confirmed by dynamic mechanical thermal analysis performed on both EDC37 and its binder. Similarities between the compressive strain rate/temperature data sets can be understood by temperature–time superposition; data collected at a strain rate of 10−3 s−1 over a temperature range 208 to 333 K were mapped onto a plot of strain rate dependent strength at 293 K, using an empirically determined sensitivity of −13.1 ± 0.3 K per decade of strain rate. Sample size was noted to have a modest effect on the stress–strain behaviour; small length to diameter ratios gave results consistent with an increased degree of confinement. Samples taken to large strains exhibited strain localization in the form of shear bands.

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.

Many high-strain-rate compression measurements (2000 per second) using a specially designed split Hopkinson pressure bar (SHPB) for the plastic-bonded explosive PBX9501 have been reported in the literature, but there is a sparsity of data for a United Kingdom polymer-bonded explosives (PBX) known as EDC37. Both EDC37 and PBX9501 are cyclotetramethylenetetranitramine-based (HMX-based) PBXs with high filler contents. The binder systems for the PBXs are very different: EDC37 consists of a nitroplasticized nitrocellulose and PBX9501 a nitroplasticized ESTANE. PBX9501 exhibits nearly invariant fracture strains of~1.5 pct as a function of temperature at high strain rates, whereas EDC37 fails at~2 to 2.5 pct. The maximum compressive strengths for both PBXs were measured at 150 Mpa at -55°C, but at +55°C, the PBX was found to have a maximum strength of~55 MPa compared with~20 MPa for EDC37. Both PBXs exhibit an increasing loading moduli, E, with increasing strain rate or decreasing temperature.

No abstract

No abstract

No abstract

Abstract. A review of imaging techniques which can be used to acquire three dimensional data on polymer composite materials is presented. The techniques chosen utilise a variety of contrast forming mechanisms including x-ray, nuclear magnetic resonance and optical & electron microscopy. Discussion is illustrated with reference to a particular HMX based UK PBX. The achievable contrast and spatial resolutions are considered, with arguments relating to destructive and non-destructive methods of acquiring data. The eventual use of this work will be in computational modelling.