CERES :: Browsing by Author "Appleby-Thomas, Gareth J."

Browsing by Author "Appleby-Thomas, Gareth J."

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Open Access
Application of shell jetting analysis to determine the location of the virtual origin in shaped charges
(Elsevier, 2018-07-25) Agu, Henry; Hameed, Amer; Appleby-Thomas, Gareth J.
Shaped charges are designed to produce high-velocity jets for penetration. During jet formation, the liner collapses and converges at a point source, also known as the virtual origin (VO), along the distance–time plane. The location of the VO must be known to allow the development of penetration analytical models. Here we determined the location of the VO using the ANSYS® Autodyn 2D shaped charge jetting technique. Jetting analysis was conducted for two shaped charges of 18 and 32 mm diameter. The explosive and casing were represented by Eulerian two-dimensional finite difference grids, whereas the liner was modelled using a shell formulation. The summary/history of the jetting analysis was used to determine the VO position in the shaped charges. Interpolating the point of intersection on the liner between the jet velocity (U-Jet) and the cumulative jet mass revealed the location of the VO at a distance equivalent to approximately two-thirds of the inner cone diameter of the shaped charges, in agreement with earlier studies based on different methods. Validation of this technique using the DiPersio, Simon and Merendino (DSM) model based on the Allison-Vitalli equation also showed good agreement with the numerical results.
Open Access
Bacterial survival following shock compression in the GigaPascal range
(Elsevier, 2017-09-01) Hazael, Rachael; Fitzmaurice, Brianna C.; Foglia, F.; Appleby-Thomas, Gareth J.; McMillan, P. F.
The possibility that life can exist within previously unconsidered habitats is causing us to expand our understanding of potential planetary biospheres. Significant populations of living organisms have been identified at depths extending up to several km below the Earth's surface; whereas laboratory experiments have shown that microbial species can survive following exposure to GigaPascal (GPa) pressures. Understanding the degree to which simple organisms such as microbes survive such extreme pressurization under static compression conditions is being actively investigated. The survival of bacteria under dynamic shock compression is also of interest. Such studies are being partly driven to test the hypothesis of potential transport of biological organisms between planetary systems. Shock compression is also of interest for the potential modification and sterilization of foodstuffs and agricultural products. Here we report the survival of Shewanella oneidensis bacteria exposed to dynamic (shock) compression. The samples examined included: (a) a "wild type" (WT) strain and (b) a "pressure adapted" (PA) population obtained by culturing survivors from static compression experiments to 750 MPa. Following exposure to peak shock pressures of 1.5 and 2.5 GPa the proportion of survivors was established as the number of colony forming units (CFU) present after recovery to ambient conditions. The data were compared with previous results in which the same bacterial samples were exposed to static pressurization to the same pressures, for 15 minutes each. The results indicate that shock compression leads to survival of a significantly greater proportion of both WT and PA organisms. The significantly shorter duration of the pressure pulse during the shock experiments (2-3 μs) likely contributes to the increased survival of the microbial species. One reason for this can involve the crossover from deformable to rigid solid-like mechanical relaxational behavior that occurs for bacterial cell walls on the order of seconds in the time dependent strain rate.
Open Access
The bactericidal effect of shock waves
(Institute of Physics, 2014-05-07) Leighs, J. A.; Appleby-Thomas, Gareth J.; Wood, David C.; Goff, Michael J.; Hameed, Amer; Hazell, P. J.
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.
Open Access
Ballistic behaviour of explosively shattered alumina and silicon carbide targets
(Maney Publishing, 2011-12-31T00:00:00Z) Nanda, H.; Appleby-Thomas, Gareth J.; Wood, D. C.; Hazell, P. J.
The resistance offered by three ceramic materials of varying strength that have been subjected to explosive loading has been investigated by depth-of- penetration testing. Each material was completely penetrated by a tungsten carbide cored projectile and the residual penetration into a ductile aluminium alloy backing material was measured. The resulting ballistic performance of each damaged ceramic was found to be similar implying that the resistance offered to the projectile by the damaged ceramic is not dependent on the intrinsic strength properties of the intact material. This was taken as evidence that the important controlling parameter for enhancing the ballistic performance of a damaged ceramic material was not the strength of the ceramic but rather the fragment morphology.
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
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
Comparison of the microstructure of machined and laser sintered shaped charge liner in the hydrodynamic regime
(Springer, 2019-07-30) Agu, Henry; Hameed, Amer; Appleby-Thomas, Gareth J.
To gain further insight into the mechanisms underlying jet formation and elongation of laser sintered shaped charge liners under high strain rate deformation, Cu–Cr–Zr alloy liners fabricated by selective laser sintering process were deformed by explosive detonation. Their as-manufactured (liner) and resultant (slug) microstructure have been investigated in comparison with those of traditional machined liners employing both optical and scanning electron microscopy. The resultant slug microstructure of both machined and laser sintered liners revealed a smaller refined equiaxed grain size consistent with traditionally fabricated liners, characteristic of dynamic recrystallization. The disappearance of the (originally present) pores in the post-shot/recovered material microstructure was observed for laser-sintered liners. Comparison of the forward and rear region of the slug revealed variations in liner deformation, a result attributed to temperature variation across the slug. In contrast with the machined liner, a unique feature of precipitation, observed in the ending (slug) microstructure of the laser sintered liner is indicative of the associated extreme high strain and strain rate liner deformation which occurred during slug formation. The precipitates are likely compounds of Chromium and Zirconium which are constituents of the laser sintered copper alloy—the first time this observation is reported. This study provides a link between post charge evolution microstructure and liner manufacturing processes, potentially providing a new route to help optimise jet formation and effectiveness.
Open Access
Constitutive model for fibre reinforced composites with progressive damage based on the spectral decomposition of material stiffness tensor
(Elsevier, 2022-05-11) Vignjevic, Rade; Djordjevic, Nenad; Galka, Agata; Appleby-Thomas, Gareth J.; Hughes, Kevin
Complex nature of the fibre reinforced composites, their non-homogeneity and anisotropy make their modelling a challenging task. Although the linear – elastic behaviour of the composites is well understood, there is still a significant uncertainty regarding prediction of damage initiation, damage evolution and material failure especially for a general loading case characterised with triaxial state of stress or strain. Consequently, simplifying assumptions are often unavoidable in development of constitutive models capable of accurately predicting damage. The approach used in this work uses decomposition of the strain energy based on spectral decomposition of the material stiffness tensor and an assumption that each strain energy component represent free energy for a characteristic deformation mode. The criteria for damage initiation are based on an assumption that the damage corresponding to a deformation mode is triggered when the strain energy for that mode exceeds a specified critical limit. In the proposed model the deformation modes are not interacting at continuum scale due to orthogonality of the eigenvectors, i.e. the stiffness tensor symmetry. Damage and its evolution are modelled by reduction of the principal material stiffness based on the effective stress concept and the hypothesis of strain energy equivalence. The constitutive model was implemented into Lawrence Livermore National Laboratory (LLNL) Dyna3d explicit hydrocode and coupled with a vector shock Equation of State. The modelling approach was verified and validated in a series of single element tests, plate impact test and high velocity impact of hard projectile impact on an aerospace grade carbon fibre reinforced plastic. The model accurately predicted material response to impact loading including the test cases characterised by presence of shock waves, e.g. the plate impact test. It was also demonstrated that the model was capable of predicting damage and delamination development in the simulation of the high velocity impact tests, where the numerical results were within 5% of the post impact experimental measurements.
Open Access
Damping of post-impact vibrations
(Elsevier, 2019-08-22) Muster, Michael; Amer, Hameed; Wood, David C.; Appleby-Thomas, Gareth J.; Wasmer, Kilian
During the impact of a body on a plate, flexural waves are set which travel circularly outwards from the point of impact. These waves can be used to determine the properties of the impacting body. For accurate measurements, it is advantageous if both the flexural and compression waves pass the sensor just once without being backscattered or reflected from the boundaries. In this paper, various plate shapes are analysed to evaluate the shape which offers the best damping properties against an impact. Experimental analysis indicated that the reflection of the flexural waves can be halved using a plate with star-shaped 60° edges with a damping layer. The damping properties can be further doubled by using a star-shaped plate with power law edges in combination with a damping layer which is attached to the edges. The work reported here offers a possible solution to get significant damping properties. This is achieved by combining a damping layer with edge shaping against a strong single excitation event. The results demonstrate that it is a promising approach for an impact detection systems which could be equally applicable to acoustic damping applications.
Open Access
Deviatoric response of an armour-grade aluminium alloy
(AIP American Institute of Physics, 2009-12-31T00:00:00Z) Appleby-Thomas, Gareth J.; Hazell, P. J.; Millett, J.; Bourne, Neil K.; Buttler, W. T.
Aluminium alloys such as 5083 H32 are established light-weight armour materials. As such, the shock response of these materials is of great importance. The shear strength of a material under shock loading provides an insight into its ballistic performance. In this investigation embedded manganin stress gauges have been employed to measure both the longitudinal and lateral components of stress during plate-impact experiments over a range of impact stresses. In turn, these results were used to determine the shear strength and to investigate the time dependence of lateral stress behind the shock front to give an indication of material response.
Open Access
The dynamic behaviour of a modified polyurethane resin
(2011-06-15) Appleby-Thomas, Gareth J.; Hazell, P. J.; Stennett, C.; Cooper, G.; Cleave, R.
The dynamic response of both a pure and nano-reinforced polyurethane replacement resin (PRR) have been investigated using plate impact techniques. Similar U-P-U- S Hugoniot equations of state have been established for both materials, despite the altered cross-linking associated with the addition of inorganic polyhedral oligomeric silsesquioxane (POSS) blocks of c. 1.5 nm size to the resin matrix. At higher particle velocities a similar U-P-U-S response to that of polyurethane from the literature was observed. However, at lower particle velocities a non- linear response was noted in both forms of PRR, similar to that observed for polymers elsewhere. Ultrasonic measurements were also undertaken and indicated the presence of two distinct phases in the reinforced elastomer.
Open Access
The dynamic behaviour of ballistic gelatin
(AIP American Institute of Physics, 2009-12-31T00:00:00Z) Shepherd, C. J.; Appleby-Thomas, Gareth J.; Hazell, P. J.; Allsop, D. F.
In order to characterise the effect of projectiles it is necessary to understand the mechanism of both penetration and resultant wounding in biological systems. Porcine gelatin is commonly used as a tissue simulant in ballistic tests because it elastically deforms in a similar manner to muscular tissue. Bullet impacts typically occur in the 350–850 m/s range; thus knowledge of the high strain-rate dynamic properties of both the projectile and target materials are desirable to simulate wounds. Unlike projectile materials, relatively little data exists on the dynamic response of flesh simulants. The Hugoniot for a 20 wt.% porcine gelatin, which exhibits a ballistic response similar to that of human tissues at room temperature, was determined using the plate-impact technique at impact velocities of 75–860 m/s. This resulted in impact stresses around three times higher than investigated elsewhere. In US−uP space the Hugoniot had the form US = 1.57+1.77 uP, while in P−uP space it was essentially hydrodynamic. In both cases this was in good agreement with the limited available data from the lit
Open Access
The dynamic response of dense 3 dimensionally printed polylactic acid
(Springer, 2019-05-22) Agu, Henry; Hameed, Amer; Appleby-Thomas, Gareth J.; Wood, David
Polylactic acid (PLA) is commonly used as a feedstock material for commercial 3D printing. As components manufactured from such material become more commonplace, it is inevitable that some of the resultant systems will be exposed to high strain-rate/impact events during their design-life (for example, components being dropped or even involved in a high-speed crash). To this end, understanding the shock properties of polylactic acid, in its role as a major raw material for 3D printed components, is of particular importance. In this work, printed samples of PLA were deformed by one-dimensional shock waves generated via the plate impact technique, allowing determination of both the Hugoniot Equation of State (EOS) and shear strength of the material. Both linear and non-linear EOS forms were considered in the US-Up plane, with the best-fit found to take the general form US=1.28+3.06−1.09Up2" role="presentation" style="display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border-width: 0px; border-style: initial; position: relative;">US=1.28+3.06−1.09U2pUS=1.28+3.06−1.09Up2 in the Us−Up" role="presentation" style="display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border-width: 0px; border-style: initial; position: relative;">Us−UpUs−Up plane, consistent with other polymers. Use of lateral Manganin gauges embedded in the material flow allowed consideration of lateral stress evolution at impact pressures ranging from 0.3 to 4.0 GPa. Shear strength was observed to increase with impact stress, however, with minimal strengthening behind the shock front. Deviation of the measured stress from the predicted elastic measurement (corresponding to the PLA’s Hugoniot Elastic Limit) was observed at longitudinal stress of 0.90 ± 0.05 GPa, within range of polymeric materials of similar characteristics—the first time this important parameter has been measured for PLA. As a result, this material characterisation will allow numerical modellers to accurately predict the structural response of PLA-based components/structures against high strain rates such as impacts or drops.
Open Access
The effects of 3D printed material properties on shaped charge liner performance
(Cranfield University, 2019) Agu, Henry; Hameed, Prof. A.; Appleby-Thomas, Gareth J.
Shaped charges operate by explosively loading a (typically metallic) liner to produce a jet travelling at extremely high velocity (9-12 km/s). Such explosive loading involves highly non-linear transient phenomena. As such, a very wide range of physical processes must be considered to enable accurate characterisation of such events – with material behaviour within these (pressure / strain-rate) regimes providing insight into problems ranging from shaped charge performance itself through to formation of new material phases at high pressures. Unlike other high strain impact events, the shaped charge phenomenon results in hydrodynamic material flow of the liner which is an integral aspect of the shaped charge design. As such, the study of shaped charge liners has been the subject of numerous scientific research studies for over 50 years since its discovery. When explosively loaded, the liner is stretched extensively during their elongation to form a jet. The jet length depends on the ductility of the liner material, and this is strongly linked to the microscopic crystal structure, which depends on the original material properties and the processes used to produce the liners. There are several processes currently used for liner production. This thesis outlines the different liner production techniques, their advantages/disadvantages and explores the potential of employing additive manufacturing (3D printing) technique for shaped charge liner production. As 3D printed parts are being considered as a possible replacement for conventionally processed parts, this PhD work fits into this long-term vision; with built parts compared in density and mechanical strength to their bulk material equivalents. More so, 3D printing is shown to present some potential benefits for the production of efficient liners including high precision, cost-effectiveness and the potential to realise customized geometries. The use of fine powders may also allow alternative microstructures to be produced with potentially interesting results. This element of the study forms the first part of this thesis, aimed at investigating the mechanism elucidating the performance of 3D printed liners processed through direct metal laser sintering process (selective laser sintering) and filament deposition modelling processes (Polylactic Acid). The next part of this work provided additional insights on the additive manufactured processed employed through investigation of the dynamic behaviour of polylactic acid, employed in the filament deposition modelling process and static (optical and scanning micrographs) observation of the laser sintered liners in their as - manufactured and deformed state, in comparison with traditional machined liners. Autodyn 2D numerical hydrocode was employed to understand how temperature influences the deformation pattern (grain refinement); providing new insights on liner deformation. Finally, a novel computational technique to determine the Virtual Origin of shaped charges was developed to provide a ready route to predict more accurate SC performance.
Open Access
The effects of changing chemistry on the shock response of basic polymers
(2016-07-11) Millett, J.; Brown, E. N.; Gray III, G. T.; Bourne, Neil K.; Wood, D. C.; Appleby-Thomas, Gareth J.
The shock response of four common semicrystalline thermoplastic polymers—polyethylene (PE), polyvinylchloride (PVC), polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE)—have been studied in terms of their Hugoniots, release velocities and shear strengths. Through the variations in behaviour caused by changes to the attached atoms to the carbon backbone, it has been possible to suggest that there are two main factors in play. The first is an electrostatic repulsion between adjacent polymer chains. Where this force is large, for example in PTFE with highly electronegative fluorine atoms, this results in this force dominating the shock response, with low shock velocities, high release velocities and little if no hardening behind the shock front. In contrast, in materials such as PE, this force is now weaker, due to the lower electronegativity of hydrogen, and hence this force is easier to overcome by the applied shock stress. Now the main factor affecting shock behaviour is controlled by the shape of the polymer chain allowing inter chain tangling (tacticity). This results in higher shock velocities, lower release speeds and significant hardening behind the shock front as the chains are forced together. This is prevalent in materials with a relatively open structure such as PE and is enhanced with the presence of large side groups or atoms off the main polymer chain.
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
Fragmentation studies by non-explosive cylinder expansion technique
(Elsevier, 2020-09-04) Rao, Prakash; Painter, Jonathan; Appleby-Thomas, Gareth J.; Critchley, Richard; Wood, David; 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
Gas gun ramp loading of Kel-F 81 targets using a ceramic graded areal density flyer system
(Elsevier, 2015-03-06) Goff, Michael J.; Hazell, Paul J.; Appleby-Thomas, Gareth J.; Wood, David C.; Stennett, Christopher
Kel-F 81 (PCTFE/Polychlorotrifluoroethylene) polymer targets were subjected to ramp loadings generated by a ceramic flyer accelerated into the targets by a gas gun in the plate impact configuration. This approach used a ceramic graded areal density flyer in conjunction with a ceramic buffer plate to induce a ramp loading in the target. The flyer was comprised of a rapid prototyped alumina ceramic. The loading was observed with embedded electromagnetic particle velocity gauges (PV gauges) with the results compared with ANSYS Autodyn™ hydrocode simulations. Experimental results show that ramp loadings of varying duration and magnitude were induced into the target. These loadings can be described as shockless compressions leading to shocked states within the material. In addition, numerical simulations provided further insight into the loading approach – with good agreement found with experimental data, opening the potential to design more complex loading systems in future.
Open Access
Impact, penetration, and perforation of a bonded carbon-fibre-reinforced plastic composite panel by a high-velocity steel sphere: An experimental study
(Professional Engineering Publishing, 2010-12-31T00:00:00Z) Hazell, P. J.; Appleby-Thomas, Gareth J.; Kister, G.
In this work, the response of a bonded CFRP composite panel, manufactured by bonding two laminates together, to impact, penetration and perforation by a high-velocity steel sphere has been studied. The response of a relatively thick (c.a. 12 mm) laminate has been compared to similar data from [1] where relatively thin monolithic laminates were impacted by the same type of projectile. It was found that the ballistic performance of the system was increased over the impact energy range of interest when compared to these similar relatively thin composite laminates. Furthermore, both the energy absorbed per-unit-thickness of laminate and the level of damage as measure by C- Scan was similar when the panels were perforated at normal and oblique incidence. This raises the prospect of reducing experimental testing at oblique angles, if the behaviour at normal incidence is known.
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.