Explosive weapons may cause damage through both blast loading and fragmentation of their casings. Although air-detonated ordnance has been extensively studied, fragmentation hazards from underwater munitions remain underexplored, and therefore no standardised procedure exists to calculate safe standoff distances as a function of depth and charge mass in naval environments. This significantly hampers the safety planning process for underwater explosives ordnance disposal activities. Building on prior laboratory investigations of underwater fragmentation, this study extends the analysis toward full-scale applicability by estimating maximum fragmentation ranges and applying injury-criteria models to assess associated hazard limits. A series of well-controlled small-scale experiments compared cased explosive charges detonated in air and at varying submersion depths. Three casing configurations were tested to quantify the influence of depth and casing configuration type on fragment generation, in-flight behaviour, and size-velocity distributions. High-speed videography and in-situ witness panels were utilised to track fragmentation post-detonation and estimate velocities during flight and after impact. An in-house analysis code with optical and panel data was developed to compute fragment trajectories, maximum ranges, and soft-tissue penetration probabilities using established injury thresholds. Results indicate a pronounced reduction in fragment count, velocity and launch angle with increasing submersion depth, producing substantially shorter predicted penetration distances for all tested submerged charges. This paper outlines a practical methodology for scaling experimental observations toward larger charge masses and discusses implications for risk assessment and mitigation during underwater munitions clearance operations.

Explosions increasingly occur in densely populated, urban locations. Primary blast injuries (PBIs), caused by exposure to blast wave overpressure, can be predicted using injury criteria, although many are based on idealised loading scenarios that do not necessarily reflect real life situations. At present, there is limited understanding of how, and to what extent, blast-structure interaction influences injury risk, and the suitability of injury criteria that assume idealised loading. This work employed computational fluid dynamics to investigate the influence of blast interaction effects such as shielding and channelling on blast load characteristics and predicted PBIs. The validated modelling showed that blast interaction with common urban features like walls and corners resulted in complex waveforms featuring multiple peaks and less clearly defined durations, and that these alter potential injury risk maps. For example, blast shielding due to corners reduced peak overpressures by 43%–60% at locations behind the corner. However, when the urban layout included a corner and a wall structure, higher pressures and impulse due to channelling were observed. The channelling significantly increased the injury risk at the exposed location and reduced the shielding effects behind the corner. In these cases, the application and interpretation of existing injury criteria had several limitations and reduced reliability. This demonstrates that structural-blast interaction from common urban layouts has a significant effect on PBI risk. Specific challenges and further work to develop understanding and reliability of injury prediction for urban blast scenarios are discussed.

Explosions in an urban setting can have a significant negative impact. There is a need to further understand the loading effects caused by the blast’s interaction with structures. In conjunction with this, the effects of scaling and understanding the limitations of laboratory experiments are equally important given the cost incurred for full-scale experiments. The aim of this study was to determine the scaling effects on blast wave parameters found for reduced-scale urban blast scenario laboratory experiments. This paper presents the results of numerical modelling and physical experiments on detonating cuboidal PE-4 charges and measuring the pressure in direct line of sight and at three distinct positions around the corner of a small-scale “building” parallel to the rear wall. Two scales were used, namely 75% and 100%. Inter-scaling between 75% and 100% worked fairly well for positions shielded by the corner of the wall. Additionally, the lab-scale results were compared to similar (but not identical) field trials at an equivalent scale of 250%. The comparison between lab-scale idealised testing and the larger-scale field trials published by Gajewksi and Sielicki in 2020, indicated sensitivity to factors such as detonator positioning, explosive material, charge confinement/mounting, building surface roughness, and environment.

Lattice structures have shown potential for efficient protection against dynamic loading events, especially during high-strain rate scenarios such as a blast. Additive manufacturing enables the design of complex geometries to optimise lattice architecture and increase blast resistance. However, the lack of experimental data related to blast-resistant lattice structures poses challenges in developing and validating theoretical and numerical models. This study aims to design blast-resistant lattice structures that can improve protection efficiency at wider applicability in high-strain rate loadings. For that, hybrid-layered Triply Periodic Minimal Surfaces (TPMS) lattice structures were systematically designed using a Design of Experiments (DoE) approach and manufactured using additive manufacturing (AM). The Blast Hopkinson Pressure Bar (BHPB) rig was used to compare the influence of different lattice topologies and relative densities on energy absorption when specimens were subjected to compressive blast loading. High-speed imaging was utilised to measure transient deformation in addition to the load transferred through the specimens. The experimental results indicated that the BHPB rig could appropriately measure the energy absorption of compressive structures subjected to shockwave loading. Additionally, the results demonstrated that TPMS topology and relative density changes substantially affect its performance. The DoE approach was utilised to predict the performance improvements of layered-hybrid lattice structures, providing valuable data for blast protection specialists and engineers designing AM lattice structures to resist blast loading.

This paper presents experimental work to characterise the dynamic behaviour of aluminium matrix syntactic foams subjected to compression, Split Hopkinson Pressure Bar and terminal ballistic impact tests as well as blast loading. Numerical models have also been developed to simulate the dynamic response of the composite foams. The effect of strain-rate on their compressive crush behaviour has been investigated, given that the ratedependent characteristics of these materials are required for designing dynamically loaded structures. Characterisation of the behaviour of the foam under high strain-rate loadings and the identification of the underlying failure mechanisms were also undertaken to evaluate their effective mechanical performance. The results show that the aluminium syntactic foam is sensitive to strain-rate in terms of initial stiffness, peak stress and plateau stress and show a pronounced high-rate dependence at a strain rate above 1000 s-1. The concrete damage plasticity model with rate-dependent features were used to simulate the dynamic behaviour of the foams, with the failure modes being captured. The model was verified and validated against the experimental results, and predictions were made for the normal and oblique ballistic impact response. Overall, the level of agreement between the numerical simulations and the experimental results is encouraging.

Over the last two decades, highly publicized disasters caused by explosions have become an all too frequent occurrence [...]

This paper reports results from an experimental and computational study on the influence of bend radius and internal angle on the damage and impulse transfer characteristics of flexible steel V-structures subjected to localized explosion loading. This issue has bearing on the manufacturing of V-hulls used for Mine Resistant Ambush Protected vehicles used around the world. Global impulse transfer, damage and transient deformation were measured during small-scale explosive detonations on 1:8-scale V-structures. The work found that increasing the bend radius to values that can be used in practical manufacturing generated damage that was less localized than the damage observed in V-structures with tighter bend radii. High-speed imaging was able to measure transient deformation that was maximal in the centre, and lower elastic post-peak vibration magnitudes at high charge masses. The impulse transfer increased as the bend radius increased and the internal V-angle increased. Since V-structures with tighter bend radii exhibit less permanent deformation and higher deformation gradients, they will be more prone to localized ruptures when deployed for blast protection, whereas structures with larger tip radii will need a larger region of the V-structure repaired after a blast event but may be less prone to rupturing when the blast loading is localized.

‘Primary’ blast injuries (PBIs) are caused by direct blast wave interaction with the human body, particularly affecting air-containing organs. With continued experimental focus on PBI mechanisms, recently on blast traumatic brain injury, meaningful test outcomes rely on appropriate simulated conditions. Selected PBI predictive criteria (grouped into those affecting the auditory system, pulmonary injuries and brain trauma) are combined and plotted to provide rationale for generating clinically relevant loading conditions. Using blast engineering theory, explosion characteristics including blast wave parameters and fireball dimensions were calculated for a range of charge masses assuming hemispherical surface detonations and compared with PBI criteria. While many experimental loading conditions are achievable, this analysis demonstrated limits that should be observed to ensure loading is clinically relevant, realistic and practical. For PBI outcomes sensitive only to blast overpressure, blast scaled distance was demonstrated to be a useful parameter for guiding experimental design as it permits flexibility for different experimental set-ups. This analysis revealed that blast waves should correspond to blast scaled distances of 1.75

As the use of more sustainable natural fibres and bio-based resins in fibre reinforced polymers (FRPs) becomes more widespread, their susceptibility to damage due to explosive detonation needs to be evaluated. In this paper, flax and jute FRP panels were blast tested and compared to equivalent mass glass FRP panels. Comparisons were made between flax and glass FRPs manufactured using a synthetic Prime 20 epoxy and a Super Sap epoxy resin containing bio-based raw materials. The transient measurements revealed that all the FRPs exhibited high-peak displacements and viscously damped elastic vibrations. The results showed the predominance of fibre strength and stiffness, and the lesser influence of resin system. The presented modified non-dimensional analysis approach could be extended to predict peak displacement of FRPs during blast events in the future. The failure mode progression for each panel type was identified, providing unique and detailed insights for designers and blast protection engineers. The work should prove valuable to blast protection engineers considering the effects of explosive detonations on structures containing FRPs.

There is currently a poor understanding of blast behaviour of natural fibre composites, yet these materials are extensively used in various other applications. An experimental study was carried out to examine the behaviour of flax fibre reinforced epoxy composites and a South African locally produced medium density fibreboard subjected to uniform blast loading. The transient response was similar for both materials and showed that the evolution of the mid-point displacement was viscous elastic and damped. A similar cracking pattern was observed on the surfaces; however, a different cracking phenomenon were found along the cross-section.

This paper presents insights into the influence of ball size on the flight characteristics and damage of a ball bearing embedded in a rear detonated cylindrical charge. It includes results from a post-test damage analysis of ball bearings from previously reported experiments. Computational simulations using Ansys Autodyn were used to provide extra information about the velocity variation during flight and the damage sustained by the ball bearings during the blast event. The influence of bearing size (diameter and mass) was investigated using the validated simulation models to extend the dataset beyond the initial experimental work. The peak bearing velocity is influenced by the charge mass to ball bearing mass ratio and the aspect ratio of the charge. Larger ball bearings require extra momentum to accelerate them to higher velocities, but their higher surface area means a greater portion of the explosive charge is involved in transferring kinetic energy to the projectile. Tensile spalling was to be the major damage mechanism within the ball bearings. The charge aspect ratio also influenced the hydrostatic pressure propagation within the ball bearing itself, affecting the location and degree of internal cracking within the bearings. These findings will prove valuable to blast protection engineers considering the effects of embedded projectiles in improvised explosive devices.

The ability to measure the structural and material response to air-blast loading is vital to developing a proper understanding of near-field blast loading and response. Computational modelling has advanced significantly but, until recently, experimental techniques lagged behind. This paper discusses recent advances in these experimental techniques. The first part describes a bilateral test programme between the UK and South Africa. The high-speed imaging and digital image correlation system at Cape Town gives repeatable and accurate impulse distributions across a central strip of a panel, useful for model validation. Flexural wave behaviour was observed from the transient velocity and displacement profiles, giving good insights into the mechanics of plate response from blast loads. The second part demonstrates the value of high-speed stereo-imaging for measuring the transient response of blast loaded fibre reinforced polymer panels and sandwich structures. The peak displacements. elastic rebounds and transient oscillations provide valuable insights into the damage propagation within these types of structures. The final part of the paper describes some of the continued developments since the success of those early trials, resulting in a new optical diagnostics for blast capability at the University of Sheffield. The imaging system operates at higher frame rates and can cover a wider region of interest on the structure. Ultra-high speed imaging is also shown to be a useful tool for visualising detonations fronts in explosive charges and the expanding fireball.

Blast injuries remain a serious threat to defence and civilian populations around the world. 'Primary' blast injuries (PBIs) are caused by direct blast wave interaction with the human body, particularly affecting aircontaining organs. Work to define blast loading conditions for injury research has received relatively little attention, though with a continued experimental focus on PBIs and idealised explosion assumptions, meaningful test outcomes and subsequent clinical applications, rely on appropriate simulated conditions. This paper critically evaluates and combines existing PBI criteria (grouped into those affecting the auditory system, pulmonary injuries and brain trauma) as a function of idealised blast wave parameters. For clinical blast injury researchers, analysis of the multi-injury criteria indicates zones of appropriate loading conditions for human-scale test items and demonstrates the importance of simulating blast conditions that are both realistic and relevant to the injury type. For certain explosive scenarios, spatial interpretation of the 'zones of relevance' could support emergency response and hazard preparedness by informing triage, patient management and resource allocation, thus leading to improved health outcomes. This work will prove useful to clinical blast injury researchers, blast protection engineers and clinical practitioners involved in the triage, diagnosis, and treatment of PBIs.

This paper presents insights into the response and failure of medium density fibreboard (MDF) panels subjected to air-blast loading. The MDF panels are representative of a cheap, and potentially sustainable, structural material that is commonly used in homes and buildings. Simplified computational simulations were used to design a series of air-blast experiments to elucidate a range of responses and failures within the MDF. The blast-loaded MDF panels exhibited multiple surface cracks, substantial in-plane cracking throughout the less dense parts of the cross-section, and fragmentation failures. The transient results show MDF exhibits peak displacement that are many times greater than the permanent deformation, and that the internal damage due to cracking reduced the stiffness of the panels. These findings provide unique and detailed insights into the cracking and fragmentation of MDF that will prove valuable to blast protection engineers considering the effects of explosive detonations inside buildings containing MDF furnishings, and any increased risk of secondary blast injuries due to flying MDF debris. The experimental data can be used by modellers to validate simulations of damage due to explosive events in the future.

Mine resistant ambush protected vehicles often use mono‐V structures in the design of their hulls for blast protection purposes. These hulls deflect blast waves laterally in the event of a landmine detonation directly beneath the vehicle. Lower internal angles offer greater deflection capability, reducing the impulse transfer to the vehicles, but at the cost of increased ride height. This paper reports results of attempts to improve on V‐hull structural designs for air‐blast loading applications, where scaled blast tests are performed to evaluate the designs in terms of structural deformation, rupture and impulse transfer characteristics. Structures with double V and W profiles are compared to mono V structures with a 120° internal angle, such that the proposed designs do not increase the ride height. Results showed that the double V‐structures limit the central deformation, but some designs have severe deformation at the interface of the central V plate and the shallow base angle structure. W structures seem to be susceptible to rupture at low charge masses. There is no single answer to improved blast protection of vehicle hulls, as design choices must be driven by the anticipated threat range, the important performance metrics and other operational considerations.

This paper presents insights into the blast response of sandwich panels with lightweight foam cores and asymmetric (different thicknesses) glass fibre epoxy face sheets. Viscously damped elastic vibrations were observed in the laminates (no core), while the transient response of the sandwich panels was more complex, especially after the peak displacement was observed. The post-peak residual oscillations in the sandwich panels were larger and did not decay as significantly with time when compared to the equivalent mass laminate panel test. Delamination was the predominant mode of failure on the thinner facesheet side of the sandwich panel, whereas cracking and matrix failure were more prominent on the thicker side (which was exposed to the blast). The type of constituent materials used and testing conditions, including the clamping method, influenced the resulting failure modes observed. A probable sequence of damage in the sandwich panels was proposed, based on the transient displacement measurements, a post-test failure analysis, and consideration of the stress wave propagation through the multilayered, multimaterial structure. This work demonstrates the need for detailed understanding of the transient behaviour of multilayered structures with significant elastic energy capacity and a wide range of possible damage mechanisms. The work should prove valuable to structural engineers and designers considering the deployment of foam-core sandwich panels or fibre reinforced polymer laminates in applications when air-blast loading may pose a credible threat.

This paper presents the unique failure characteristics, such as fragmentation, internal cracks, general deformation and pitting, observed on a SS420C ball bearing from direct blast loading using a cylindrical PE-4 explosive. Axisymmetric simulations were performed to gain insights of the failure mechanisms. While additional work is needed to fully understand all characteristic found, valuable findings have been presented to explain some of the failures.

•Numerical analysis used to derive spherical equivalence of cylindrical explosives.•Kinetic energy uptake used to equate between cylinders and spheres.•Aspect ratio 0.2≤L/D≤5 and scaled distance 0.108≤Z≤0.485 studied.•Results compiled into design charts to rapidly convert between cylinders and spheres.•Accuracy demonstrated using verification exercise, accurate to 1%.

This paper presents new insights into the influence of explosive charge backing on the impulse transfer and transient response characteristics of plates subjected to close-proximity air blast loading. The results of the combine experimental and computational studies show the critical influence of charge backing, which caused between a 3-5 times increase in the impulse transfer when the charge was metal-backed. The permanent deflections from the metal-backed detonations were larger than for air, but not to the same degree as the impulse increase. These findings demonstrate the important influence of charge backing, in close proximity detonations, which greatly exceeded anything previously measured. These valuable insights will assist blast protection engineers considering the effects of explosions in situations when the charge backing is something other than air, which is a frequent occurrence in explosion scenarios.

This paper presents an all-Mach method for two-phase inviscid flow in the presence of surface tension. A modified version of the Hartens–Lax–van Leer Contact (HLLC) solver is developed and combined for the first time with a widely used volume-of-fluid (VoF) method: the compressive interface capturing scheme for arbitrary meshes (CICSAM). This novel combination yields a scheme with both HLLC shock capturing as well as accurate liquid–gas interface tracking characteristics. It is achieved by reconstructing non-conservative (primitive) variables in a consistent manner to yield both robustness and accuracy. Liquid–gas interface curvature is computed via height functions and the convolution method. We emphasize the use of VoF in the interest of interface accuracy when modelling surface tension effects. The method is validated using a range of test-cases available in the literature. The results show flow features that are in sensible agreement with previous experimental and numerical work. In particular, the use of the HLLC-VoF combination leads to a sharp volume fraction and energy field with improved accuracy.