Penetration performance of protective materials from crossbow attack: a preliminary study.

Crossbow-related injuries resulting in serious and mortal consequences have increased in recent years, and although significant research exists for both injury and fatality on the human body, limited data exists on the lethality of the bolt and the failure modes of protective materials. This paper concerns itself with the experimental validation of four differing crossbow bolt geometries, their effects on material failure and potentially lethality. During this study, four different types of crossbow bolt geometries were tested against two protection mechanisms that differed in mechanical properties, geometry, mass and size. The results show that at 67 ms-1, ogive, field and combo tips do not provide lethal effect at 10-m range, whilst a broadhead tip will perforate both the para-aramid and a reinforced area of polycarbonate material consisting of two 3-mm plates at 63-66 ms-1. Although perforation was apparent with a more honed tip geometry, the chain mail layering within the para-aramid protection and friction caused by polycarbonate petalling on the arrow body reduced the velocity enough to demonstrate the materials under test are effective at withstanding crossbow attack. Subsequent calculation of the maximum velocity that arrows could achieve if fired from the crossbow within this study shows results close to the overmatch value of each material and therefore a requirement to advance the knowledge in this field to influence the development of more effective armour protection mechanisms.

Sustainable and economical alternatives to fragment capture materials in explosive and ballistic trials.

Strawboard has been utilised as a fragmentation capture material since the 1960s, mainly employed to capture fragments from explosives and explosive devices from arena trials of munitions. As this material has historically been calibrated to a known standard, it has a proven record of allowing research establishments to ascertain the velocity of a fragment based on the depth of penetration of the strawboard. During the time of calibration, strawboard was used as a common building material which was both widely available and relatively affordable; however, due to the recent economic crisis and geopolitical supply issues, this is no longer the case. Building on initial testing, this paper investigates alternatives to strawboard to determine if a cheaper, more readily available material can be used instead. The alternatives are compared and judged based on the NATO ARSP-03 guideline for capture material which includes metrics such as price and attainability, as well as assessing environmental impact and its ability to be used as a viable alternative to strawboard in an explosive environment. Based on these NATO guidelines, explosive fragmentation and ballistic experiments were conducted, and ten materials were tested based on the following criteria: Handling, Density, Flammability, Calibration, Cost and Availability. Medium Density Fibreboard (MDF) was found to be a suitable alternative to strawboard. The data demonstrates that it provides the same capture performance as strawboard at approximately a quarter of the cost and is far more readily available. Other materials also showed potential and further testing should be undertaken to validate these materials as alternatives to MDF.

Quantification of fragmentation capture materials and an assessment of the viability of economical alternatives: a preliminary study.

High pressure, high-temperature events need to be quantified experimentally. Where fragmentation occurs, i.e. against personal protective equipment, there is a requirement for both a reliable and repeatable measurement of numerous experimental metrics. Typically, the most critical is calculating the energy absorbed by the target material, to characterize target performance. This is achieved by detonating a device and capturing a proportion of the fragmentation in a suitable material that can achieve successful recovery of all fragmentation produced. Therefore, allowing the estimation of the target's response using the depth of penetration within the capture material which allows the calculation of energy absorption. The current standardized fragmentation capture material used within the UK is known as strawboard. Although effective, this material is both expensive and limited in its availability. This study explores the classification of strawboard to provide a suitable baseline to compare against medium density fibreboard (MDF) and flooring underlay, which represent two more economically friendly alternatives on the openmarket. It was found that the uniformity of response for the MDF material was better than that of strawboard, due to its reproducibility between batches and velocity ranges. To further explore this phenomena, high explosive trials were conducted, further demonstrating MDF to be a viable, reliable and cheaper alternative. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'.

Ballistic protective properties of material representative of English civil war buff-coats and clothing.

One type of clothing system used in the English Civil War, more common amongst cavalrymen than infantrymen, was the linen shirt, wool waistcoat and buff-coat. Ballistic testing was conducted to estimate the velocity at which 50% of 12-bore lead spherical projectiles (V50) would be expected to perforate this clothing system when mounted on gelatine (a tissue simulant used in wound ballistic studies). An estimated six-shot V50 for the clothing system was calculated as 102 m/s. The distance at which the projectile would have decelerated from the muzzle of the weapon to this velocity in free flight was triple the recognised effective range of weapons of the era suggesting that the clothing system would provide limited protection for the wearer. The estimated V50 was also compared with recorded bounce-and-roll data; this suggested that the clothing system could provide some protection to the wearer from ricochets. Finally, potential wounding behind the clothing system was investigated; the results compared favourably with seventeenth century medical writings.

Ballistic research techniques: visualizing gunshot wounding patterns.

There are difficulties associated with mapping gunshot wound (GSW) patterns within opaque models. Depending on the damage measurement parameters required, there are multiple techniques that can provide methods of "seeing" the GSW pattern within an opaque model. The aim of this paper was to test several of these techniques within a cadaveric animal limb model to determine the most effective. The techniques of interest were flash X-ray, ultrasound, physical dissection, and computed-tomography (CT). Fallow deer hind limbs were chosen for the model with four limbs used for each technique tested. Quarantined 7.62 × 39 mm ammunition was used for each shot, and each limb was only shot once, on an outdoor range with shots impacting at muzzle velocity. Flash X-ray provided evidence of yaw within the limb during the projectile's flight; ultrasound though able to visualise the GSW track, was too subjective and was abandoned; dissection proved too unreliable due to the tissue being cadaveric so also too subjective; and lastly, CT with contrast provided excellent imaging in multiple viewing planes and 3D image reconstruction; this allowed versatile measurement of the GSW pattern to collect dimensions of damage as required. Of the different techniques examined in this study, CT with contrast proved the most effective to allow precise GSW pattern analysis within a cadaveric animal limb model. These findings may be beneficial to others wishing to undertake further ballistic study both within clinical and forensic fields.

Experimental fragmentation of pipe bombs with varying case thickness.

Among all the improvised explosive devices (IEDs) known, pipe bombs are one of the most popular devices used by terrorists. They are simple to use, easy to construct and materials are readily available. For this IED, fragmentation is the primary injury mechanism, which makes them a desirable weapon for terrorists aiming to inflict maximum human casualties. Although the investigation of fragmentation pattern is not novel, there is limited data available on pipe bombs performance in the open literature. Therefore, this research is looking at validating results in current literature, which showed limited repetition and weak experimental design so far; by trial with six pipe bombs with two different thickness (3 of each). The pipe bombs consisted of mild steel casing and aluminised ammonium nitrate as the explosive filler. Fragments were collected, with an average recovery of 72%, and measured regarding mass and velocity. The experiment results show a correlation between the pipe thickness and both the size and velocity of fragments.

Experimental and computation assessment of thermomechanical effects during auxetic foam fabrication.

Auxetic foams continue to interest researchers owing to their unique and enhanced properties. Existing studies attest to the importance of fabrication mechanisms and parameters. However, disparity in thermo-mechanical parameters has left much debate as to which factors dominate fabrication output quality. This paper provides experimental, computational, and statistical insights into the mechanisms that enable auxetic foams to be produced, using key parameters reported within the literature: porosity; heating time; and volumetric compression ratio. To advance the considerations on manufacturing parameter dominance, both study design and scale have been optimised to enable statistical inferences to be drawn. Whilst being unusual for a manufacturing domain, such additional analysis provides more conclusive evidence of auxetic properties and highlights the supremacy of volumetric compression ratio in predicting Poisson's ratio outcomes in the manufacture process. Furthermore statistical results are exploited to formulate key recommendations for those wishing to maximise/optimise auxetic foam production.