[en] Recent results have strongly suggested that the ballistic-resistance of different comminuted ceramics is similar, independent of the original strength of the material. In particular, experimental work focused on the ballistic response of such materials has suggested that ballistic response is largely controlled by shattered material morphology. Consequently, it has been postulated that control of the nature of ceramic fragmentation should provide a potential route to optimise post-impact ballistic resistance. In particular, such an approach would open up a route to control in multi-hit capabilities. Here, ballistic tests into pre-formed 'fragmented-ceramic' analogues assembled from compacted alumina powders with two differing morphologies were conducted. Strong hints of a morphology-based contribution to ballistic resistance were apparent, although there was insufficient fidelity in the experimental data set to categorically identify the nature of this contribution.

[en] We have subjected the aluminium alloy 7010-T7651 to shock loading. A heterodyne velocimeter system was used to interrogate both the HEL and dynamic tensile failure (spall). It was shown that the HEL in the short transverse direction is higher than in the longitudinal direction whereas the spall strength is higher in the longitudinal direction. The increased HEL in the short-transverse direction is thought to be due to the increased number of grain boundaries due to the highly elongated nature of the grains along the rolling direction. The spall strength was measured and compared with other high-strength aluminium alloys and was found to be 1.61 GPa ± 0.19 GPa in the longitudinal direction and 1.20 GPa ± 0.01 GPa in the short-transverse direction.

[en] There are a variety of theories relating to the origins of life on our home planet, some of which discuss the possibility that life may have been spread via inter-planetary bodies. There have been a number of investigations into the ability of life to withstand the likely conditions generated by asteroid impact (both contained in the impactor and buried beneath the planet surface). Previously published data regarding the ability of bacteria to survive such applied shockwaves has produced conflicting conclusions. The work presented here used an established and published technique in combination with a single stage gas gun, to shock and subsequently recover Escherichia coli populations suspended in a phosphate buffered saline solution. Peak pressure across the sample region was calculated via numerical modelling. Survival data against peak sample pressure for recovered samples is presented alongside control tests. SEM micrographs of shocked samples are presented alongside control sets to highlight key differences between cells in each case

[en] A requirement exists to generate realistic insults in energetic targets, for example ramp loadings leading to shock waves. This paper examines the development of a ceramic flyer ramp wave generation technique. Ceramic stereolithography was used to produce fully-dense, graded areal density alumina ceramic flyers. These flyers consisted of multiple square pyramids arranged on a solid base. The gas gun plate impact and electromagnetic particle velocity gauge techniques were used to observe the ramp waves generated when the flyers impacted a Kel-F 81 polymer target. Ramp waves of varying properties were successfully generated in the targets, and good agreement was obtained with 3D hydrocode modelling

[en] Scatter and non-linearity of the Hugoniot in the Us-up plane has been seen in a number of polymers including poly(methyl methacrylate) (PMMA), the polymer considered here. In this study the plate impact technique has been used to investigate the shock response of PMMA between particle velocities of 0.13 and 0.77 mm μs⁻¹. From this data no scatter was seen between our data and the experimental data of Barker and Hollenbach, and Carter and Marsh. Also a linear Hugoniot in the U_s-u_p plane was found, with the equation U_s = 2.99 + 0.92u_p. The non-linearity observed by Barker and Hollenbach was not present in this data, probably due to the non-linearity occur at particle velocities of below 0.13 mm μs^-1, within their experimental data. Gruneisen gamma has also been briefly considered using a shock reverberation experiment but more work is needed before a value can be ascertained.

[en] Laterally orientated manganin stress gauges have been used to obtain strength measurements in multiple materials, most commonly polymers and metals. Composites such as carbon fibre provide an interesting challenge for lateral gauges, as any long range order within the composite will be broken up by the inclusion of the gauge. This study has investigated the shear strength of multiple orientations of a carbon fibre composite (TWCP) which has then been compared with the matrix material. The Hugoniot elastic limit of the 90° fibre weave TWCP composite was 2.27±0.25 GPa, compared to 1.53±0.20 GPa found for the fibre weave orientated at 0^° with respect to the shock front. The lateral stress in both orientations however, was found to be the same, at a given particle velocity. This implies that either the matrix material dominates the lateral stress behaviour of this composite, or laterally orientated gauges are too intrusive and break up any long range order of the fibre weave. Further work utilising other strength assessment techniques will be employed to fully validate these experimental results.

[en] A number of experiments were carried out using a modified version of the standard particle velocity gauge technique in plate impact experiments with inert targets. Unusually these utilised dynamic metallic elements. Traditional methodology advises against the use of metallic flyers/barriers with this technique as conductive objects moving in the magnetic field produce perturbations in the output gauge voltage leading to inaccuracies in the derived particle velocities. This body of work investigated the causes of the perturbation effect, methods of minimising its magnitude and possible post-processing correction methods. In experiments with Al flyers, perturbations on the order of 10-15% of signal strength were observed. While the magnitude of the voltage traces were distorted, key features such as shock impact could still be observed, and shock tracker gauges were still effective. The case of metallic barriers was also examined and similar effects observed. This study has indicated that while a coarse empirical correction is possible, uncertainty in the validity of the correction would preclude the use of dynamic metallic elements in experiments where high fidelity data is required.

[en] In this paper the shock response of CrS, a cermet of potential interest as a matrix material for ballistic applications, has been investigated. Compacts with a Chromium: Sulfur ratio of 1.15:1 were investigated via the plate-impact technique. These experiments allowed the material to be loaded under a one-dimensional state of strain. Embedded manganin stress gauges were employed to monitor the temporal evolution of longitudinal and lateral components of stress. Comparison of these two components has allowed assessment of the variation of material shear strength both with impact pressure/strain-rate and time.

[en] Three different orientations of a tape-wrapped carbon fibre composite with phenolic resin matrix (abbreviated to TWCP) have been investigated under one-dimensional shock loading. This has been achieved via a single-stage gas gun, with manganin gauges as the diagnostic tool. The orientations of TWCP studied in this paper were 25°, 45° and 90°, with respect to the impact face. The shock response of these orientations, for this material, has been obtained (the Hugoniot equation of state). These results have been contrasted with previously reported literature data for the same material at different orientations (0° and 20°). It was found that orientation had minimal effect on the behaviour of this composite under shock. The exception to this was the 90° orientation which exhibited an elastic precursor at particle velocities of less than 0.65 mm µs⁻¹; where the shock velocity was equivalent to the elastic sound speed of the material.

[en] Despite its fundamental nature, the process of dynamic tensile failure (spall) is poorly understood. Spall initiation via cracks, voids, etc, before subsequent coalesce, is known to be highly microstructure-dependant. In particular, the availability of slip planes and other methods of plastic deformation controls the onset (or lack thereof) of spall. While studies have been undertaken into the spall response of BCC and FCC materials, less attention has paid to the spall response of highly anisotropic HCP materials. Here the dynamic behaviour of zirconium is investigated via plate-impact experiments, with the aim of building on an ongoing in-house body of work investigating these highly complex materials. In particular, in this paper the effect of impact stress on spall in a commercially sourced Zr rod is considered, with apparent strain-rate softening highlighted.