CERES :: Browsing by Author "Painter, Jonathan"

Browsing by Author "Painter, Jonathan"

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Open Access
Characterisation of human tissues analogues for ballistic testing
(None - paper only available to conference delegates, 2023-08-30) Appleby-Thomas, Gareth J.; Khan, Irfan Ullah; Painter, Jonathan; Zioupos, Peter; Lordachescu, Alexandra; Hes, Roelof A. G.
Ballistic testing necessarily employs simulant target materials for ethical and fiscal reasons. Current tissue analogues utilised for ballistic testing / research are, however, typically relatively simplistic – such as ballistics soap or gelatin. Consequently, these materials are seldom representative of complex mammalian constructs. In this paper the authors have drawn together core elements of previously published in-house research with the aim of providing insight into potential approaches to create a composite simulant solution. In particular, tissue analogues covering the epidermal, epithelial, connective, muscular and skeletal components are presented. These results highlight the complementary nature of employing a range of tissue simulant materials and, in parallel, the importance – if ballistic testing data is to be truly representative – of fully understanding the nature of the analogues employed.
Open Access
Chemical characteristics of macroscopic pyrogenic carbon following millennial-scale environmental exposure
(Frontiers, 2020-01-21) Ascough, Philippa L.; Brock, Fiona; Collinson, Margaret E.; Painter, Jonathan; Lane, David W.; Bird, Michael I.
Pyrogenic Carbon (PyC) is ubiquitous in global environments, and is now known to form a significant, and dynamic component of the global carbon cycle, with at least some forms of PyC persisting in their depositional environment for many millennia. Despite this, the factors that determine the turnover of PyC remain poorly understood, as do the physical and chemical changes that this material undergoes when exposed to the environment over tens of thousands of years. Here, we present the results of an investigation to address these knowledge gaps through chemical and physical analysis of a suite of wood PyC samples exposed to the environment for varying time periods, to a maximum of >90,000 years. This includes an assessment of the quantity of resistant carbon, known as Stable Polyaromatic Carbon (SPAC) versus more chemically labile carbon in the samples. We find that, although production temperature is likely to determine the initial ‘degradation potential’ of PyC, an extended exposure to environmental conditions does not necessarily mean that remaining PyC always progresses to a ‘SPAC-dominant’ state. Instead, some ancient PyC can be composed largely of chemical components typically thought of as environmentally labile, and it is likely that the depositional environment drives the trajectory of preservation versus loss of PyC over time. This has important implications for the size of global PyC stocks, which may have been underestimated, and also for the potential loss of previously stored PyC, when its depositional environment alters through environmental or climatic changes.
Open Access
A comparison of the ballistic behaviour of conventionally sintered and additively manufactured alumina
(Elsevier, 2019-06-20) Appleby-Thomas, Gareth J.; Jaansalu, Kevin; Hameed, Amer; Painter, Jonathan; Shackel, James
Production of ceramic armour solutions on-demand/in-theatre would have significant logistical and military advantages. However, even assuming that such technologies could be successfully deployed in the field, such near net-shape manufacturing technology is relatively immature compared to conventional sintering of ceramics. In this study, the ballistic performance of a series of additively manufactured (AM)/rapidly-prototyped (RP) alumina tiles of 97.2% of the density of Sintox FA™ were investigated using both forward- and reverse-ballistic experiments. These experiments, undertaken with compressed gas-guns, employed the depth-of-penetration technique and flash X-ray as primary diagnostics to interrogate both efficiency of penetration and projectile-target interaction, respectively. The RP alumina was found to exhibit useful ballistic properties, successfully defeating steel-cored (AP) 7.62 × 39 mm BXN rounds at velocities of up-to c.a. 850 m/s, while exhibiting comparable failure modes to conventionally sintered armour-grade Sintox FA™. However, where a <1% by vol. Cu dopant was introduced into the RP material failure modes changed dramatically with performance dropping below that of conventionally sintered alumina. Overall, the results from both sets of experiments were complimentary and clearly indicated the potential of such RP materials to play an active role in provision of real-world body armour solutions provided quality control of the RP material can be maintained.
Open Access
The effects of quasi-one-dimensional shock on Escherichia coli while controlling pressure and temperature
(Elsevier, 2020-11-28) Fitzmaurice, Brianna C.; Appleby-Thomas, Gareth J.; Painter, Jonathan; Wood, David C.; Hazael, Rachael
The response of microorganisms to high pressures is of growing interest in the literature, regarding areas of research including the sterilisation of foodstuffs, panspermia and, more generally, the study of extremophiles. When examining organisms under shock pressure, there are a number of caveats that need to be considered, including temperature and the nature of the shock wave front. Both of these caveats have been explored in this study through the application of the plate impact technique to create quasi-one-dimensional shock waves with controlled shock fronts through bacterial targets. This was achieved using typical planar flyer plates to study the dynamic pressure response of the bacterium, Escherichia coli NCTC 10538. Additionally, in order to create an adiabatic, off-Hugoniot loading path, a novel graded areal density flyer produced by the Surfi-Sculpt® approach was used to assess the effects of lowering temperature during shock on E. coli growth rates. The maximum temperature generated by a Surfi-Sculpt® flyer impact was 5 K less than that produced by the planar flyer analogue. Higher growth rates of bacterial colonies post-impact by the Surfi-Sculpt® flyer compared to those by the planar flyer were observed, with this behaviour determined to be a possible function of the nature, although temperature was also decreased with the use of this adiabatic ramp loading technique. In an effort to purposefully increase pressure and temperature for the E. coli samples, a modified form of a previously developed bacterial encapsulation system was also employed in this study, allowing pressures of up to 10 GPa and growth rates of up to 0.09% to be reached.
Open Access
Environmental taphonomic processes and their effects on skeletal trauma analysis
(2019-07) Vachirawongsakorn, Vijarn; Marquez-Grant, Nicholas; Painter, Jonathan
In recent years there has been extensive research focusing on skeletal trauma as a result of different types of weapons inflicted on bone. However, an important factor that has not been investigated in depth is the potential modification to the observed dimensions and morphology of trauma marks after environmental exposure. Detailed information derived from traumatic lesions to bone is highly valuable in forensic anthropological casework. It is important to understand how taphonomic variables, namely the outdoor environment or fire, may alter trauma morphology. Therefore, the aim of this study is to evaluate the influence of different environmental taphonomic agents on fresh and burned bone trauma that have been inflicted by either blunt or sharp instruments. This research used blunt and sharp weapons to inflict trauma on manually macerated porcine ribs (n=364) and femurs (n=60). Subsequently each specimen was examined, analysed, and photographed. Qualitative and quantitative analyses were undertaken using macroscopic, microscopic and radiological techniques to investigate specific traumatic lesions, such as cut and chop marks, as well as bluntinflicted fractures. The traumatised bones were subsequently deposited on the surface or in a buried environment for a pre-determined length of time (6, 12 and 18 months). In addition, sharp force trauma was inflicted on ribs which were then burned at 850°C in a furnace prior to being buried or placed on the surface for 1 month. The samples were then re-examined and the trauma evidence was compared between pre- and post-environmental exposure. The results showed several trends. Surface colour and taphonomic alterations were linked to macro- and micro-environmental factors, and were also dependent on the duration of environmental exposure. Surface-deposited samples underwent higher degrees of degradation than buried samples. In addition, perimortem blunt and sharp force traumatic lesions on the ribs and femurs were still clearly identifiable after 18-month environmental exposure. This study also illustrated that taphonomic modifications of blunt and sharp injuries were different depending on the interaction between bone, the type of trauma and the surrounding environment. Fractures from different types of weapon showed dissimilar responses to environmental variables. ii Pre-exposure bone and different types of depositional environment had an effect on the rate and pattern of taphonomic modifications on dimensions and morphology of the traumatic lesion. The results of this study should enable an improved determination of skeletal trauma analysis after environmental exposure. Moreover, this study has emphasised the need for a combination of macroscopic, microscopic and radiological techniques to analyse taphonomic phenomena. As environmental factors have the potential to conceal perimortem skeletal trauma, this study advises that when carefully examining traumatic lesions on ribs and femurs as an alteration of their dimensions and morphology is likely to have occurred after prolonged environmental exposure.
Open Access
Failure modes of CFRP panels under hypervelocity impact: the effects of strain rate between 1 km/s and 6 km/s
(ASME, 2024-12-31) Lawrence, Jacob; Painter, Jonathan; Iordachescu, Alexandra; Footer, Charles J.; Seabright, Ryan M.; Appleby-Thomas, Gareth
Studying the effects of hypervelocity impacts on structural materials is essential for the aerospace and defense fields. However, there is a paucity of open-source and accessible data in the literature concerning the hypervelocity impact response of CFRP composites. This paper details our results from an experimental research program designed to aid in addressing this limitation by providing extensive data from multiple analysis techniques. This is part of a wider body of research focused on identifying failure modes and their evolution at elevated strain rates. Experimental work on the impact of commercially available CFRP composites at impact velocities between 1000 and 6000 m/s is presented and discussed. This work provides further validation for the response of an aerospace-relevant material to extreme loading conditions, with wider implications for the design and use of these structures in various industries. Preliminary results from optical imaging, HSV capture, SEM, VP-SEM, and target mass loss analysis are included and show a strain rate dependence in the CFRP material studied.
Open Access
Fragmentation studies by non-explosive cylinder expansion technique
(Elsevier, 2020-09-04) Rao, Prakash; Painter, Jonathan; Appleby-Thomas, Gareth J.; Critchley, Richard; Wood, David C.; Roberts, Andrew; Hazael, Rachael
Expansion and fragmentation of metallic cylinders is an important area of study both for designing munitions and mitigation techniques against fragments as well as in the failure of pressurised pipes in industry. Most of the reported studies on fragmentation have been carried out by detonating explosively filled metallic cylinders. However, this approach has inherent limitations in terms of both safety and repeatability – not least due to packing issues with explosive fills. Fragmentation studies on hollow metallic cylinders of both mild and stainless steel of various thicknesses (2–4 mm) were carried out by firing a polycarbonate projectile from a single-stage light gas gun. Strain rates of the order of 2 × 104 s−1 were observed at cylinder expansion velocities of 400–450 m s−1, calculated from flash X-ray radiographs. The differences in fragmentation behaviour of both materials was observed, attributed to their different response to high strain-rate loadings. Microscopic analysis of mild steel fragments showed interesting alignment of ferrite and pearlite grains, similar to reported effects of explosive loading. This suggests the potential to employ this technique to simulate explosive cylinder expansion in a non-explosive laboratory environment enabling a convenient recovery of fragments. Numerical modelling with using ANSYS AUTODYN® allowed for a better understanding of the various parameters controlling expansion and fragmentation. Analysis of recovered fragments by a Fragment Weight Distribution Map (FWDM), a method generally used for characterising pipe bombs, could clearly demonstrate the effect of casing material and thickness.
Open Access
The importance of considering both depth of penetration and crater volume in forwards-ballistic penetrative experiments
(AIP, 2023-09-26) Powell, Dan; Appleby-Thomas, Gareth J.; Painter, Jonathan; Brock, Fiona; Thirulogasingam, Thiru; Sagoo, Kam; Brown, Nick; Livesey, Chris
The most common method of analysing armour performance is the Depth of Penetration (DoP). However, this one-dimensional measurement does not provide insight into the method of penetration or energy absorbed by the target; the crater could be particularly narrow or very wide and yield the same DoP. Analysis of the crater through Crater Volume (CV) provides a more detailed metric to be used alongside DoP to visualise the crater, indicating whether energy was dispersed over a large area. CV provides a wider insight into how a material resisted penetration events, giving evidence of potential defeat mechanisms. Digital reconstruction of the craters using X-ray radiographs or Computed Tomography (CT) scanning can also provide a useful tool for computational models to be compared against. The simple calculation of CV through X-ray radiography and image processing has been demonstrated to be accurate to within ±6% of the CT scanned CV. Success in utilising this analytical tool was demonstrated through comparison of three armour configurations. A consistent difference in the ratio of DoP:CV was seen between steel targets, ceramic-steel targets and ceramic-air-steel targets, indicating variation in the defeat mechanism between the three target configurations.
Open Access
Improving adhesion in bonded ceramics through novel additively manufactured surface geometries
(Cranfield University Defence and Security, 2024-11-13) Powell, Daniel; Appleby-Thomas, Gareth; Painter, Jonathan
Many high-value industries (including medical, aerospace, and defence) utilise ceramics for their favourable properties, such as high hardness, low thermal / electrical conductivity, and chemical resistance. The latter property results from chemical inertness. However, this inertness leads to weaker bond strengths when joining ceramics with other materials, as is often required to overcome their brittle nature and low tensile strength.Geometries can be introduced to the surface of a material to act as adhesion promoters through increasing the surface area of the bond, but more interestingly through mechanical interlocking between the ceramic and bonding material. Whilst this would be impossible to achieve through conventional manufacturing techniques, additive manufacturing (AM) can create these novel surface geometries. This work pushes the capabilities of ceramic AM at a scale of no greater than 500 µm, finding the limits of the current technology. Furthermore, the potential for increased bonding through the generated geometries is investigated.
Open Access
Inelastic deformation and failure of tungsten carbide under ballistic-loading conditions
(Elsevier , 2010-12-31T00:00:00Z) Hazell, Paul J.; Appleby-Thomas, Gareth J.; Herlaar, K.; Painter, Jonathan
High-speed photography has been used to investigate the dynamic behaviour of similar grades of WC-Co hardmetals during ballistic impacts with velocities in the range of 28-484 m/s. Key features of the failure of similar grades of WC-Co materials during complimentary impacts have been observed and discussed. In particular, fast moving fragments were observed to emanate from the point of impact and flow radially across the target's surface analogous to the processes of interface defeat. Further, as the velocity of impact was increased a non-linear increase in the indentation depth was observed that corresponded with an apparent onset of trans-granular fracture in the WC crystallites. Comparisons with ANSYS AUTODYN™ simulations were made and good correlation has been established between the measured inelastic deformation and computations using a simple strain-hardening model.
Open Access
Internally bevelled conoidal entry wounds in sandwich bones; their genesis, impact dynamics and macroscopic and microscopic morpholog
(Cranfield University, 2021-01) Rickman, John; Painter, Jonathan; Hazael, Rachael
Projectile trauma to the sandwich bones of the neurocranium is of considerable forensic anthropological importance due to the high lethality associated with gunshot wounds to this anatomical region. The internally bevelled conoidal wound that typically results from perpendicular projectile impact has long been considered diagnostic of bullet involvement and is utilised in both differential diagnosis of gunshot trauma and in making trajectory determinations using the direction of bevel asymmetry as an indicator. However, despite the importance of these activities in forensic anthropological casework the fracture mechanisms underlying bevel formation have remained elusive, with multiple hypotheses presented but few empirical investigations carried out to test them. Further diagnostic complexity has been introduced by the recognition that bevelling also results from low-velocity impacts and that taphonomic agencies can both modify and create internally bevelled fractures. Despite the fact that bone is a complex hierarchical material the majority of analyses of projectile entry wounds in sandwich bones have been conducted at the macroscopic scale, leaving important questions as to whether lower scales of organisation may yield signatures of diagnostic importance. This thesis presents the findings of an experimental investigation into the fracture mechanisms that underlie internal bevelling and presents an analysis of the relationships between the dynamics of impact and quantitative wound morphology. A refined nomenclature for the components of internally bevelled fractures is presented and the layers composing the bevel formally defined. This thesis also presents a Scanning Electron Microscope (SEM) analysis of the effects of projectile impact on compact bone at lower hierarchical scales of bone organisation. Examination of fracture morphology with micro-computerised tomography (µ-CT) coupled with high-speed videography of the impact events revealed a novel cone cracking mechanism that fundamentally changes our understanding of bevel morphology. This mechanism explains how internal bevelling results from both low- and high-velocity impact events and suggests caution should be applied to trajectory determinations made using bevel asymmetry alone. Quantitative analysis of the perforation event revealed, for the first time in sandwich bones, a power relationship between incident velocity and absorbed kinetic energy. SEM analysis of cortical bone around the entry captured the early genesis of conoidal wounds through ring crack formation. Analysis of the periphery of the entry revealed two types of plastic deformation that are suggestive of changes to hydroxyapatite (HA) crystal structure that may be of diagnostic utility. Collectively, the findings presented in this thesis will enhance the diagnosis and interpretation of conoidal wounds in both forensic and archaeological contexts.
Open Access
An investigation into the use of a vehicle for improvised blast mitigation
(Institute of Explosives Engineers, 2022-03-31) Flynn, Daniel; Charters, Robert; Mangham, Patrick; Swallowe, Daniel; Tudor, Matthew; Harris, Michael; Painter, Jonathan
The Problem. Improvised explosive devices (IED) and/or vehicle borne IEDs (VBIED) are a worldwide threat and will remain so for the foreseeable future. Once located, the immediate response of the local security personnel would be to evacuate the area whilst specialists are called in to deal with the device. However, there may be circumstances that mean that bystanders cannot be moved, such as through prior injury, and therefore there is a need to investigate methods of rapid improvised blast mitigation. One such option is a vehicle as it could be moved quickly into position. But as there are a wide variety of vehicle shapes and sizes, as well as the need to optimise the positioning for maximum mitigation effectiveness, Hertfordshire Constabulary approached Cranfield University to assist in studying the feasibility of this tactic. The project was allocated to a syndicate undertaking the Addressing EOE Capability Caps (AECG) Module of the Explosive Ordnance Engineering (EOE) MSc. The four-person syndicate consisted of both civilian and serving military personnel, two of whom were on the first phase of their Ammunition Technical Officers Course.
Open Access
An investigation into the variability of ABS 3D printing filaments due to differing dye colourants used by manufacturers
(2019-12) Wright, Gary; Shackel, James; Errickson, David; Painter, Jonathan
Despite advances in polymer filaments available for 3D printing, ABS remains an attractive polymer for use because of its versatility, good mechanical properties and cost effectiveness. Personal experience has highlighted variability between manufacturer’s ranges and even occasionally between the colours within those ranges. This variability seems to affect the quality of print and level of success achieved. In this study, analytical techniques, including X-ray diffraction (XRD), Dynamic Mechanical Analysis (DMA), Differential Scanning Calorimetry (DSC), RAMAN spectroscopy, and Fourier Transform Infra-Red (FTIR) spectroscopy, as well as mechanical tensile testing and Scanning Electron Microscopy (SEM) imaging, were used to compare and contrast selected colours from 3 different manufacturer’s ranges. This allowed comparison by chemical composition, physical properties such as glass transition temperature and by mechanical performance. Differences were found in their chemical composition, base polymer properties and their mechanical performance and some of this data did not match the information supplied by the manufacturers. A large analytical comparative study such as this lends itself to becoming quite complex, and this was reinforced by the practical difficulties encountered during the work which limited the conclusions that could be drawn. Significant variability was found between the manufacturer’s ranges themselves, and in some instances by colours within ranges. These differences were evident by way of DSC and DMA responses for glass transitions, compositions shown by FTIR and crystallinity from XRD, and occasionally also large statistically significant variability in mechanical tensile properties. Despite these findings, and practical experience implying otherwise, there was no conclusive link found that the variability of colour of the filament is responsible for the variability of print quality. Indeed, the variability between the base polymer i blends comparing each of the manufacturer’s ranges was found to be higher than that between the colours within the ranges themselves.
Open Access
Investigation of the high-strain rate (shock and ballistic) response of the elastomeric tissue simulant Perma-Gel®
(Elsevier, 2016-04-01) Appleby-Thomas, Gareth J.; Wood, David C.; Hameed, Amer; Painter, Jonathan; Le-Seelleur, Victoria; Fitzmaurice, Brianna C.
For both ethical and practical reasons accurate tissue simulant materials are essential for ballistic testing applications. A wide variety of different materials have been previously adopted for such roles, ranging from gelatin to ballistics soap. However, while often well characterised quasi-statically, there is typically a paucity of information on the high strain-rate response of such materials in the literature. Here, building on previous studies by the authors on other tissue analogues, equation-of-state data for the elastomeric epithelial/muscular simulant material Perma-Gel® is presented, along with results from a series of ballistic tests designed to illustrate its impact-related behaviour. Comparison of both hydrodynamic and ballistic behaviour to that of comparable epithelial tissues/analogues (Sylgard® and porcine muscle tissue) has provided an insight into the applicability of both Perma-Gel® and, more generally, monolithic simulants for ballistic testing purposes. Of particular note was an apparent link between the high strain-rate compressibility (evidenced in the Hugoniot relationship in the Us-up plane) and subsequent ballistic response of these materials. Overall, work conducted in this study highlighted the importance of fully characterising tissue analogues – with particular emphasis on the requirement to understand the behaviour of such analogues under impact as part of a system as well as individually.
Open Access
Knife cut marks inflicted by different blade types and the changes induced by heat: a dimensional and morphological study
(Springer, 2021-10-29) Vachirawongsakorn, Vijarn; Painter, Jonathan; Márquez-Grant, Nicholas;
Detailed information on skeletal trauma analysis of burned bone is important to ascertain the manner and cause of death in forensic casework. This research used three different knife types, one with a non-serrated blade, one a fine-serrated blade, and one a coarse-serrated blade, to inflict trauma to manually macerated Sus scrofa ribs (n = 240), and these ribs were later exposed to heat. Qualitative and quantitative analyses were conducted using macroscopic and microscopic techniques to assess specific characteristics of the cut marks. Differences in cut mark dimension and morphology of the ribs were investigated. After heat exposure, the cut marks on the rib samples remained recognisable and did not alter considerably. A level of dimensional and morphological preservation was reliant on the cutting action and the features of the knife blade as well as surrounding bone injury. The cut marks inflicted by the non-serrated blade remained recognisable despite exposure to the burning process. However, the cut marks inflicted by the coarse-serrated blade were likely to change significantly when exposed to heat. This study leads to two important results: (1) identification of pre-existing cut marks prior to heat exposure is possible in reconstructed burned bone fragments, and (2) cut marks from different types of knife blades showed dissimilar responses to heat. The outcomes obtained in this study stressed the need to adopt great care with the effects of heat on skeletal trauma analysis.
Open Access
Multi-impact response of CR4 mild steel: Characterising the transition from absorption to failure
(IOP Publishing, 2023-03-15) Thawani, Bonny; Batchelor, T.; Painter, Jonathan; Hazael, Rachael; Critchley, Richard
Single impact perforation shots are well understood for various target materials and different shaped projectiles. Although considered a rare case, localised multi-impacts are not well understood as they involve both perforating and non-perforating impacts on the target. The lack of understanding of non-perforating impact on metallic materials makes it tough to predict the change in the material’s mechanical performance. Given the widespread use of metallic materials for protective applications, it is important to understand the material response when subject to multiple impacts. To determine the effect of a non-perforating shot on CR4 mild steel and establish a minimum energy impact that will define the transition point whereby the metal can no longer absorb energy a series of impact experiments were conducted. Results show a subsequent perforation event occurs at a lower than the experimentally determined perforation velocity. Results suggest that there could be a direct correlation between the material thickness and the critical crater depth (the depth of crater required to affect the materials ability to absorb energy, the measure of materials performance). As the crater depth increased from 3mm to 8.5mm for the first shot, the energy absorption of the steel plate reduced by 25%. This allowed the residual performance for CR4 mild steel to be quantified for a known impact crater, giving a 7% performance loss for every millimetre the critical crater depth grows beyond 3mm until the point of failure.
Open Access
On differences in the equation-of-state for a selection of seven representative mammalian tissue analogue materials
(Elsevier, 2017-10-10) Appleby-Thomas, Gareth J.; Fitzmaurice, Brianna; Hameed, Amer; Painter, Jonathan; Gibson, Michael C.; Wood, David C.; Hazael, Rachael; Hazell, Paul J.
Tissue analogues employed for ballistic purposes are often monolithic in nature, e.g. ballistic gelatin and soap, etc. However, such constructs are not representative of real-world biological systems. Further, ethical considerations limit the ability to test with real-world tissues. This means that availability and understanding of accurate tissue simulants is of key importance. Here, the shock response of a wide range of ballistic simulants (ranging from dermal (protective / bulk) through to skeletal simulant materials) determined via plate-impact experiments are discussed, with a particular focus on the classification of the behaviour of differing simulants into groups that exhibit a similar response under high strain-rate loading. Resultant Hugoniot equation-of-state data (Us-up; P-v) provides appropriate feedstock materials data for future hydrocode simulations of ballistic impact events.
Open Access
On the effects of powder morphology on the post-comminution ballistic strength of ceramics
(Elsevier, 2016-10-29) Appleby-Thomas, Gareth J.; Wood, David C.; Hameed, Amer; Painter, Jonathan; Fitzmaurice, Brianna C.
In this paper in order to try and elucidate the effects of particle morphology on ballistic response of comminuted systems, a series of experiments were carried out via the use of powder compacts with differing initial particle morphologies. This approach provided a route to readily manufacture comminuted armour analogues with significantly different microstructural compositions. In this study pre-formed `fragmented-ceramic' analogues were cold-pressed using plasma-spray alumina powders with two differing initial morphologies (angular and spherical). These compacts were then impacted using 7.62-mm FFV AP (Förenade Fabriksverken Armour Piercing) rounds with the subsequent depth-of-penetration of the impacting projectile into backing Al 6082 blocks used to provide a measure of pressed ceramic ballistic response. When material areal density was accounted for via differing ballistic efficiency calculations a strong indication of particle morphology influence on post-impact ceramic properties was apparent. These results were reinforced by a separate small series of plate-impact experiments, whose results indicated that powder morphology had a strong influence on the nature of compact collapse.
Open Access
Optimal skin simulant for ballistic testing
(Elsevier, 2023-03-24) Hes, R. A. G.; Painter, Jonathan; Appleby-Thomas, Gareth J.
An extensive literature review, combined with practical experience of forensic testing, has identified several concerns regarding existing studies into skin simulants. These can be summarized as arising due to human skin being a highly complex, multi-layered and anisotropic material whose mechanical properties depend on many factors such as age and gender of the host. In many studies (and papers) essential information is missing. Although there is some parallelism between the studies, the reported energy density at perforation is very inconsistent (a function of the natural variation of skin properties alluded to above) and differs from 0,113 J/mm2 [1] to 0,239 J/mm2 [2]. Which is, in fact, a more than 100% variation. Such a variation is arguably insufficient to enable accurate replication with a single simulant material. Combined with the missing common agreement about the energy density threshold between countries, laboratories and researchers, this analysis clearly identifies the need for an adjustable and / or customizable skin simulant. To-date, the most often used simulation material for human skin in ballistic testing is ‘Chrome crusted cow hide’ [3]. However, this is a natural material and, consequently therefore, inevitably physically variable in nature – both inter and intra hide. Ballistic tests on 10 chrome crusted cow hides using 4,5 mm BB’s gave v50% ranging from 113 m/s to 200 m/s, an uncontrolled variability for forensic experiments. Hence, the authors examined a skin analogue that could be produced in-house, enabling tailoring to match the desired properties, and with improved consistency. To this end, a thin, 4 mm thick, layer of gelatine (30 – 45 weight %, increasing per 1 weight %) was studied. The ballistic resistance of the gelatine skin analogue was compared to the v50%’s published values in literature, with good agreement found as the gelatine concentration was varied. In comparison to the chrome crusted cow hides this suggests that this relatively simple and accessible approach has potential to provide a more consistent standard.
Open Access
Pressure tolerance of Artemia cysts compressed in water medium
(Taylor and Francis, 2019-02-04) Hazael, Rachael; Matsuda, Shinsuke; Mori, Yoshihisa; Fitzmaurice, Brianna; Appleby-Thomas, Gareth J.; Painter, Jonathan; Meersman, Filip; Richaud, Myriam; Galas, Simon; Saini, Naurang L.; Ono, Fumihisa; McMillan, Paul F.
The high pressure tolerance of cysts of Artemia salina was investigated up to several GPa in water. No survival was observed after exposure to 1.0 GPa for 15 min. After exposure to 2.0 GPa for the same time duration, the hatching rate had recovered to 33%, but decreased to 8% following compression at 7.5 GPa. This contrasts with results using Fluorinert™ as the pressure-transmitting medium where 80–88% recovery was observed. The lower survival rate in water is accompanied by swelling of the eggs, indicating that liquid H2O close to the ice-VI crystallization pressure penetrated inside the eggs. This pressure exceeds the stability limit for proteins and other key biomolecules components within the embryos that could not be resuscitated. Rehydration takes several minutes and so was not completed for all samples compressed to higher pressures, prior to ice-VI formation, resulting in renewed survival. However H2O penetration inside the shell resulted in increased mortality