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In 1989, Nurick and Martin published two review papers on the deformation of thin steel plates subjected to impulsive air-blast loading. The state of the art has progressed significantly in the following 25 years, and this review paper restricts itself to experimental studies that investigate the response of monolithic metal plates subjected to air-blast loading generated by detonating plastic explosive. From the large number of experiments reported, it is shown that the failure progressions in circular and quadrangular plates are similar and can be adequately described by three “failure modes” – namely large plastic deformation (mode I), tensile tearing (mode II) and shearing (mode III) although the severity and location of these failures on the plates is primarily determined by spatial distribution of the blast loading across the plate surface, and that boundary conditions significantly influence the onset of shearing and tearing failures due to variation in the in-plane movement of the plate material. The non-dimensional analysis approaches used by Nurick and Martin have been expanded to include the effects of load localisation and stand-off distance, and show good correlation with the expanded sets of test data published since 1989. It is concluded that these approaches still hold merit as simple tools for evaluating the likely effect of a close proximity air blast load on a flat metal plate. [ABSTRACT FROM AUTHOR]

The response of circular steel plates subjected to loading arising from the detonation of plastic explosive PE4 was investigated experimentally. The shape of the explosive charge, the charge dimensions and the charge mass were varied during the experiments. Cylindrical, truncated cone and the inverted truncated cone shaped explosives were detonated in close proximity to fully clamped circular plates fixed to a ballistic pendulum. The impulse, for the detonation of a given charge mass, was found to be highest for the inverted truncated cone. However, the maximum permanent displacement of the circular plates was greatest for the truncated cone shape. An analytical approach, combining the ZND detonation model with the concept of effective mass of explosive, was developed to gain understanding of the shape and intensity of the shock wave resulting from the explosion. The distribution of the shock wave obtained from the analytical approach was used to explain some of the experimental observations. [ABSTRACT FROM AUTHOR]

Abstract: This work considers the validity of the assumption that the influence of radial displacements and bending strains can be ignored when constructing closed form analytical solutions for the large displacement response of impulsively loaded circular plates. Three successive energy based analyses are presented. The first analysis considers only membrane strains, but includes radial displacements in addition to transverse displacements. It is shown that the inclusion of radial displacements alters the plastic strain distribution but does not alter the integral of the total energy dissipated due to plastic strain, and consequently, does not affect the final central deflection estimate. This result provides a rigorous justification for the assumption that radial displacements can be ignored. However, though neglectable, the radial displacements are not negligible and must be included in order to obtain realistic strain distributions. Thereafter, a model is presented that considers the interaction of bending and membrane strains. It is shown that at large displacements the membrane strains suppress the effect of bending strains. This result supports the assumption that bending strains can be ignored at large deflections. Furthermore, it provides an estimate for the displacement range in which the interaction between bending and membrane effects is significant and should not be ignored. Lastly, the non-monotonic nature of the strain history is considered and shown to have a small effect. [Copyright &y& Elsevier]

Abstract: Thin-walled steel hollow sections are used extensively in the construction, offshore, mining and security industries. Such members subjected to blast loads are of interest due to increased security demands and the occurrence of accidental or intentional explosive events. This paper reports an experimental and analytical investigation of steel square hollow sections subjected to transverse blast load, applied with explosive uniformly distributed along the length of the member. Three different section sizes were tested over three different lengths, and the members were fully clamped at their ends. The explosive loads were sufficient in magnitude to cause plastic deformation of the cross-section (local deformation), plastic flexural deformation of the overall member (global deformation), and tensile tearing at the supports. The energy dissipated in the local deformation is determined using rigid-plastic analysis and yield line mechanisms of the deformed cross-sections. The total input energy minus the energy dissipated in local deformation is assumed to be expended in flexural deformation. Analytical solutions using the energy consumed in flexural deformation are shown to produce bounded solutions of the transverse plastic deformation of the members. Finally, a semi-empirical solution is suggested that can be used to aid in design. [Copyright &y& Elsevier]

Abstract: This article presents the results of an experimental investigation into the performance of perforated plates as a blast wave mitigation method in tunnel-like structures. Combinations of three different blockage ratios and three different separation distances (defined as the distance between the perforated plates and target plates) were used during the blast experiments to ascertain the influence of the two variables, while the charge to target plate stand-off distance was kept constant. The results were compared to those obtained during similar test work at a lower separation distance of 25 mm, and also to baseline experiments with no perforated plate at a similar stand-off distance. Results of the blast tests showed that the perforated plates with higher blockage ratios reduced the damage imparted to the target plate. This effect was more significant at the lower separation distances. Increasing the separation distance also reduced the damage for a given blockage ratio and impulse. [Copyright &y& Elsevier]

The results of blast tests on sandwich panels with honeycomb cores are reported. Two core heights (13 mm and 25 mm) and two face sheet materials (glass fiber epoxy composite and aluminum alloy) were investigated. Increasing the core thickness reduced the permanent displacements exhibited by the sandwich panels. The panels with composite face sheets also exhibited smaller residual displacements than the aluminum face sheet counterparts. Damage took the form of core crushing, core shearing, debonding of the face sheet from the core, permanent displacement, cracking of the composite face sheets, and tearing. Higher damage levels were observed at elevated impulse levels. Load localization was found to concentrate the damage to the central portion of the panel, preventing the whole panel being employed in resisting the blast. [ABSTRACT FROM AUTHOR]

Abstract: An investigation into the response of a sandwich cladding panel under blast loading is presented. The sandwich cores are composed of square thin-walled metallic tubes. Three primary panel layouts are identified, consisting of panels with four, five and nine tubes within the core. Annealed mild steel and 6063-T6 aluminium alloy tubes are selected as the core material. Hemispherical indentation triggers are used to induce progressive, symmetric buckling. A series of experimental blast tests are conducted on the proposed panels. A ballistic pendulum is used to measure the impulse transferred to the panel. At smaller blast impulses, irregular buckling modes are observed for both the steel and aluminium tube-core panels primarily due to variable trigger performance. For blasts which utilize the full stroke of the tubes, symmetric buckling modes are observed. In all cases panel crush distance increases with increasing impulse and decreases with an increasing number of tubes in the panel core. Further to this, at equal charge mass, the aluminium tube cores show significantly higher crush distance than identical steel tube panels. Analytical predictions of panel response give satisfactory agreement with experimental and finite-element results provided the response is within the pre-compaction regime. Finite-element results using ABAQUS/Explicit also show satisfactory correlation with experimentally obtained global response. Numerical analysis shows that energy absorption is primarily confined to the core tubes with only minimal plastic strains developing in the top plate. A numerical parametric study is conducted to determine influence of load uniformity on panel response. Energy absorption efficiency is found to be highly sensitive to the uniformity of the load, primarily in panels with fewer core tubes and thinner top plates. [Copyright &y& Elsevier]

Abstract: This article presents the results of the experimental and numerical investigation into the effects of introducing welding into established laboratory scale tests of blast loaded stiffened plates. The experimental configurations, manufacturing details and results are presented. For a specific weld configuration an increasing stiffener height results in a decreasing tearing threshold. The bulge and stiffener deflection trends are independent of the weld configuration for the same stiffener height. In contrast, the tearing thresholds are strongly dependent on weld configuration and therefore the choice of weld configuration requires careful consideration during the design phase of blast protection. The numerical predictions are limited to large Mode I deflections and correlate well with the experimental trends. The results of modelling the tearing failure threshold are not included but reference to the preliminary attempts is provided. [Copyright &y& Elsevier]

Abstract: Finite element simulation is employed to analyse the behaviour of clamped sandwich panels comprising equal thicknesses mild steel plates sandwiching an aluminium honeycomb core when subject to blast loadings. Pressure-time histories representative of blast loadings are applied to the front plate of the sandwich panel. The FE model is verified using the experimental test results for uniform and localised blast loading in the presence of a honeycomb core and with only an air gap between the sandwich plates. It is observed that for the particular core material, the load transfer to the back plate of the panel depends on the load intensity, core thickness and flexibility of the sandwich panels. [Copyright &y& Elsevier]

Abstract: Tests that investigate the inelastic response of blast-loaded sandwich structures, comprising mild steel plates and aluminium alloy honeycomb cores, are reported. The “uniform” loading was generated by detonating a disc of explosive and directing the blast through a tube towards the target. Localised blast loading was generated by detonating discs of explosive in very close proximity to the test structure. The sandwich panels responded in a more efficient manner to the uniformly distributed loading, and hence the majority of the paper is concentrated on uniform loading response. The honeycomb sandwich results are compared to test results on structures with air as the core. The failure modes and interaction between the components are discussed. Three phases of interaction are identified for each sandwich structure, based upon deformation, contact, crushing and tearing responses of the sandwich components. The compromise between load transfer through the core and improved energy absorption is discussed. [Copyright &y& Elsevier]

Abstract: This paper reports on experimental and numerical investigations into the response of flexible sandwich-type panels when subjected to blast loading. The response of sandwich-type panels with steel plates and polystyrene cores are compared to panels with steel face plates and aluminium honeycomb cores. Panels are loaded by detonating plastic explosive discs in close proximity to the front face of the panel. The numerical model is used to explain the stress attenuation and enhancement of the panels with different cores when subjected to blast induced dynamic loading. The permanent deflection of the back plate is determined by the velocity attenuation properties (and hence the transmitted stress pulse) of the core. Core efficiency in terms of energy absorption is an important factor for thicker cores. For panels of comparable mass, those with aluminium honeycomb cores perform “better” than those with polystyrene cores. [Copyright &y& Elsevier]

Abstract: A series of localised blast loading experiments are performed in order to understand how the experimental set-up influences the impulse imparted to a plate. The imparted impulse is measured using a ballistic pendulum. The experimental results show that for both rigid and deformable plates the impulse measured by a ballistic pendulum increases as the height of the boundary (clamps) increases. Significantly, it is found that although the measured impulse varies as a function of the boundary height, the plate deformation is unchanged. This suggests that not all of the impulse measured by the ballistic pendulum resulted in plate deformation. Therefore, in numerical and analytical modelling, the total impulse from the ballistic pendulum should not simply be applied as a centrally localised pressure load. Numerical simulations of localised blast loading in combination with the aforementioned experimental results are used to develop a localised blast loading model. The loading model is a simplified pressure loading model which only imparts the deformation causing impulse as opposed to the total ballistic pendulum impulse. The model is validated using an independent set of localised blast load experiments on clamped mild steel plates. Results obtained using a published localised blast load model are also compared. [Copyright &y& Elsevier]

Abstract: This paper presents the results of two test programmes in which quadrangular mild steel plates are subjected to pressure loads created by exploding charges ranging from 100 to 26,288kg. The charge consists of different ordnances stacked in different configurations, namely compacted and widespread in a carpet-like form. The effects of the charge configurations on the response of the square mild steel plates are investigated. Simple analytical evaluations of the pressures and impulses are used for the purpose of comparison with the experiments. The correlation shows satisfactory agreement, despite the imperfect terrain and different complex explosive loading arrangement. [Copyright &y& Elsevier]

Abstract: This paper presents the results of blast loading tests on fully clamped square fibre metal laminate (FML) panels. The FMLs were constructed from aluminium alloy, a polypropylene interlayer and co-mingled glass fibre/polypropylene woven cloth. The spatial loading distribution is approximated as uniform and was generated by detonating annuli of explosive. Observations from blast experiments performed on panels with different stacking configurations are reported and the response compared to similar locally blast loaded FML panels. Multiple debonding, plastic deformation, internal buckling and metal tearing were all observed. In non-dimensional form, the data from both the localised and uniform blast tests collapsed onto one line for the front face displacement and another line for back face displacement. [Copyright &y& Elsevier]

Abstract: A series of experiments examining the effects of welded boundaries on the localised blast load response of mild steel plates is presented in this short communication. Two types of welding are examined, TIG and MIG welding. The welded boundary response is compared with clamped boundary and straight and chamfer machined boundary responses. The overall trend of midpoint deflection–thickness ratio versus dimensionless damage number for all the plates follows previously reported empirical trends. The tearing threshold (Mode II*) in terms of the damage number is lowest for the machined plates followed by the welded plates with the clamped plates having the highest resistance to tearing. [Copyright &y& Elsevier]

Abstract: The effect of stand-off distance and charge mass on the response of fully clamped circular mild steel plates, of radius 53 mm, subjected to blast loads travelling along tubular structures is reported. The procedure consists of creating a blast load using plastic explosive mounted onto the end of mild steel tubes. The stand-off distance is varied, from 13 to 300 mm, using different tube lengths. The plate responses range from large inelastic deformation to complete tearing at the boundary. Different loading regimes are observed, depending on the stand-off distance between the explosive charge and the plate, and are classified according to the plate response. At stand-off distances less than the plate radius (13–40 mm), the blast load is considered to be focused (localized). For stand-off distances greater than the plate radius (100–300 mm), the loading is considered uniformly distributed over the entire plate area. Theoretical and empirical analyses are performed, to enable predictions of the mid-point deflection. Appropriate modifications are introduced to account for the effect of stand-off distance on plate deformation. The modified analyses show satisfactory correlation with experimental results. [Copyright &y& Elsevier]

Abstract: This two part paper examines the behaviour of fibre-metal laminates (FMLs) subjected to localised explosive blast loading. Part I presents the experimental observations of diamond and cross-shaped back face deformation, as well as pitting, global displacement and ring-buckling of the front face are also discerned. Part II presents quantitative analysis of the experimental data. When expressed in terms of non-dimensional parameters front and back face displacements fall within one plate thickness of a linear trend line. The threshold impulse for the onset of tearing is found to increase linearly with panel thickness. [Copyright &y& Elsevier]

Abstract: Previous work on the blast response of aluminium/glass–fibre reinforced polypropylene fibre–metal laminates (FMLs) presented observations and quantitative analysis on panels of varying thickness and stacking configuration. Diamond and cross-shaped back face damage was observed and dimensionless analysis showed that the front and back face displacement fell within one plate thickness of a linear trend line [Langdon GS, Lemanski SL, Nurick GN, Simmons MC, Cantwell WJ, Schleyer GK. Behaviour of fibre–metal laminates subjected to localised blast loading: Part I – experimental observations. Int J Impact Eng, in press; Lemanski SL, Nurick GN, Langdon GS, Simmons MC, Cantwell WJ, Schleyer GK. Behaviour of fibre–metal laminates subjected to localised blast loading: Part II – quantitative analysis. Int J Impact Eng, in press]. This paper presents failure characterisation of the blast-loaded square fibre–metal laminate panels, identifying trends and failure modes for each panel type. Multiple debonding, large plastic displacement, fibre fracture and matrix cracking are identified as damage mechanisms within the panels. Back face spalling, debonding failure and front face buckling are also discussed. [Copyright &y& Elsevier]

Abstract: The response of a novel lightweight panel design under blast loading is numerically investigated. The sandwich-type panel uses thin-walled square tubes as the core material with mild steel outer plates. A parametric study is carried out with ABAQUS/Explicit to examine the effects and interaction between design variables in three different tube layouts. Tube position, thickness and aspect ratio as well as top plate thickness are varied. Buckling stability and absorption performance are shown to be highly sensitive to tube placement due to interaction effects between the top plate and tubes. For each panel an optimal tube positioning is obtained corresponding to nearly perfect axial progressive symmetric tube buckling. Tube thickness is shown to influence the onset of buckling and hence affects the stability of the core, while energy absorption performance is also highly configurable. Tube aspect ratio shows only a small effect on core buckling stability and energy absorption. Top plate thickness influences absorber performance significantly while having a small effect on buckling stability. A simple theoretical analysis is presented and shows reasonable agreement with the numerical simulations. [Copyright &y& Elsevier]

Abstract: This paper examines the behaviour of fibre metal laminates (FML’s) subjected to localised explosive blast loading. Experiments are conducted on samples of varying thickness and material distribution. Plastic deformation, debonding, delamination, fibre fracture and matrix cracking have all been identified as energy absorption mechanisms. Widespread debonding is particularly evident between layers. Comparison between different plates of similar overall thickness shows no significant improvement in blast performance with increasing number of distinct material layers. This suggests that debonding does not absorb a significant proportion of the blast energy. [Copyright &y& Elsevier]

Abstract: An experimental investigation of deformation and shear failure in peripherally clamped centrally supported (PCCS) blast loaded circular plates is presented. In particular, the timing of shear failure events and the associated magnitude of the shear forces are reported. The plates exhibited three distinct modes of failure: mode I (large ductile deformation), mode II (boundary failure after large deformation) and mode III (boundary failure prior to large deformation). Approximate energy analyses for mode I deformation of annular and PCCS plates are presented. An expression for dimensionless impulse, applicable to annular and PCCS plates, is derived. The experimental data and analytical predictions exhibit satisfactory correlation. [Copyright &y& Elsevier]

Abstract: This paper describes the numerical simulation results of two experimental studies [Teeling-Smith RG, Nurick GN. The deformation and tearing of thin circular plates subjected to impulsive loads. Int J Impact Eng 1991;11:77–91; Nurick GN, Bryant MW. Fragmentation damage as a result of an explosion. In: Gupta NK, editor. Plasticity and impact mechanics, December 1996, New Delhi, India, p. 484–498] in which the deformation and post-failure response of a plate subjected to blast loading were investigated. In Ref. Teeling-Smith and Nurick, uniform blast loading was considered, while in Ref. Nurick and Bryant, localised blast loading was investigated. The finite element code ABAQUS was used to simulate the structural response of the respective blast structures, while the hydro-dynamic code AUTODYN was used to characterise the localised blast pressure, time, and spatial history. The simulations showed satisfactory correlation with the experiments for energy input, large inelastic deformations and post-failure motion. [Copyright &y& Elsevier]

Abstract: The energy absorption of circular and square aluminium alloy tubes subjected to an axial explosive load, which is transmitted to a tube by a small attached mass, is discussed. Particular attention is paid to the interaction between the inertia of the attached mass and a tube when the importance of the initial compression phase is revealed. The effect of this phase on the mean load, which is characteristic of the energy absorption capacity of structural elements, is demonstrated. The influence of the material models on the prediction of the response of aluminium alloy circular and square tubes is also discussed in relation with the temperature effects caused by the high strain rates. The analysis shows that the material properties play an important role for the formation of the buckling pattern due to the finite duration of the initial compression phase when plastic stress waves at different speeds propagate along a shell. [Copyright &y& Elsevier]

This two-part article presents the results of experimental and numerical work on the response of built-in mild steel quadrangular plates with different stiffener configurations (unstiffened, single, double, cross and double cross), subjected to blast loading. Part I studies the response of plates to uniform blast loading, while Part II examines the response to localised blast loading. The approach in both studies is similar—experimental results obtained from blast tests, using a ballistic pendulum, are presented and compared with finite element simulations. The numerical approach consisted of adiabatic analysis of a 1/4 symmetry plate model using ABAQUS/Explicit 5.8. Both temperature-dependent material properties and strain rate sensitivity are included in the numerical modelling. Large inelastic deformation is well predicted for the various stiffener configurations and sizes for both maximum displacement and deformation shape. Tearing is predicted by high-temperature bands. [Copyright &y& Elsevier]

This paper presents an experimental investigation into the response of glassfibre chopped-strand mat laminates to air pressure blasts. Experiments were conducted with a variety of monolithic and layered targets of laminates with differing areal densities. Results of the post-impact visual inspection show three distinct damage modes: matrix cracking, delamination/debonding, and penetration as final damage. The analysis focuses on resistance to damage of these modes, damage propagation with increasing blast impulse, damage distribution in the thickness direction of the targets, and the influence of blast attenuation and large-area support on the target response. [Copyright &y& Elsevier]

This article presents an experimental and numerical investigation into the effect of charge geometry on the structural response of right circular cylinders. Thin-walled, seamless 304 stainless steel cylinders were subjected to internal blast loads that were generated by detonating bare cylindrical plastic explosive charges. Charge diameter, charge mass and aspect ratio were varied. Partial confinement was created by closing one end of the cylinder and leaving the other end free to vent to air. The axial impulse, maximum diametric deflection and axial shortening increased with increasing aspect ratio when the charge diameter was kept constant. When the charge mass was kept constant, the long charges caused larger diametric deflections than their mass equivalent shorter charges. The shorter charges transferred more axial impulse to the ballistic pendulum than their mass equivalent longer charges. The concept of effective charge mass (axial and lateral) was used to interpret the results and developed to provide an empirical equation relating deflection to the charge dimensions. Numerical simulations were performed which gave good agreement with the experimental data and predicted similar trends. The model revealed that the longer charges produced more diametric deflections than their mass equivalent shorter charges because a high pressure (above 50 MPa) zone, that covered a larger area and had a longer duration, developed at the cylinder wall in the case of longer charges. The insights from the model are in good agreement with the simple concept of lateral effective charge mass developed herein. When compared to spherical charge detonations in similar steel cylinders, the cylindrical charge detonations produced pressure waves which are more directional, have lower peak pressures and dissipate more gradually. The cylinders exhibited a more pronounced secondary bulge at the clamped boundary for cylindrical charge detonations. [ABSTRACT FROM AUTHOR]

This article presents the results of an investigation into the response of partially confined hollow stainless steel cylinders to internal air-blast loading. Numerical, theoretical and experimental analyses were performed to gain insight into the factors governing the deformation processes. Numerically, LS-DYNA was used to simulate the response of the steel single-walled cylinders and compare it to the response of various equivalent mass sandwich-walled cylinders with different mass distributions through the wall thickness. It was established that sandwich-walled cylinders with low density foam core outperform the single-walled cylinder while the higher density foam core sandwich-walled cylinders respond by larger maximum deflections compared to the single-walled equivalent. A theoretical model was developed for the deformation of a sandwich-walled ring configuration and used to analyse and interpret the process of the dynamic foam compaction and stress transmission to the outer wall of a sandwich-walled cylinder. The results from the numerical parametric study and theoretical analysis are used further to design a sandwich-walled cylinder which would outperform the equivalent mass single-walled steel tube. Experimentally, the blast loading was generated by detonating spheres of plastic explosive at the mid-point of the centre line of the cylinders. Partial confinement was created by closing one end of the cylinder and leaving the other end free to vent to air. [ABSTRACT FROM AUTHOR]

This paper present the experimental analysis of square mild steel plates subjected to blast loads in three different degrees of confinement (free air burst, fully vented and fully confined). Varying spherical masses of explosive were detonated at a constant stand-off distance from three different thickness target plates in the three different degrees of confinement to investigate the effects of confinement as well as the effect of plate thickness on the final plate deformations. Plate deformations ranging from one to fourteen plate thickness were obtained. The experimental results show that the midpoint deflection ratio between two different thickness plates subjected to identical blasts is inversely proportional to the ratio of the plate thicknesses. Equations for predicting the final midpoint deflection of square mild steel plates subjected to blast loading in the three degrees of confinement are presented. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental and numerical investigation into the response of circular Domex-700 MC steel plates to repeated uniform blast loads. The Domex 700 steel tests plates of thickness either 2 or 3 mm are mounted onto a ballistic pendulum and subjected to uniform blast load up to five times for repeated loading. In general, the plates show large inelastic global deformation with thinning occurring at the clamped boundary and in some cases tearing. A trend of increasing permanent mid-point deflection is observed for an increase in charge mass and number of witnessed blast loads. The results also show a decrease in the incremental mid-point deflection and an increase in the Vickers hardness of the plate at the boundary and central region with increasing number of witnessed blast loads. Numerical simulations are carried out to gain further insight into the deformation of plates subjected to repeated blast loading using ABAQUS/Explicit v6.10.1 in conjunction with the inbuilt blast function code, ConWep. A scaling factor is adopted to model the amplified blast wave resulting from the detonation of cylindrical charges at one end of a cylindrical tube. Very good correlation is obtained with regards to midpoint deflection and deformation profiles. The plastic strain obtained numerically shows good qualitative correlation with the experimental Vickers hardness tests. [ABSTRACT FROM AUTHOR]

Abstract: The deformation of a stationary foam block due to an impact by a foam projectile is analysed. Several combinations between the properties and geometry of the projectile and stationary block are used in order to reveal the characteristic features of deformation under the condition of decreasing velocity during the impact event. No details of the cellular geometry are analysed and it is assumed that the foam is a homogeneous material. The dynamic compaction of the foam block and projectile is described by a one-dimensional model. The model is based on the propagation of a strong discontinuity unloading wave when using the actual experimentally derived stress–strain curves for three aluminium based foam: Alporas with 9% relative density and Cymat foams with 9.3% and 21% relative density. Numerical simulations were carried out to verify the proposed model. It is shown that the strain distribution in the foam blocks significantly depends on the material properties and boundary conditions. It is shown that a more distinct boundary between the compacted and undeformed foam can be observed in the projectile while the strains in the stationary block usually decrease gradually with the increase of the distance travelled by the compaction wave from the interaction boundary. It is demonstrated that the proposed approach is capable of predicting the history and final strain distribution in the foam with sufficient accuracy. [Copyright &y& Elsevier]

Abstract: This paper presents the results of an experimental investigation to determine the effect of the height of burial (the amount of sand beneath the buried charge) on a buried charge in terms of impulses imparted onto a rigid steel target plate (suspended from a vertical pendulum). The 40 mm rigid target plate of exposed area 400 mm × 400 mm is located at a constant stand-off distance of 47 mm above the surface of the sand. Tests conducted at a height of burial of 0 mm (placed flush on a steel base plate) resulted in the largest impulse transfer for all depth of burial (amount of sand above the buried charge) values tested. The optimal depth of burial for impulse transfer was observed to occur within 50–70 mm irrespective of the height of burial (0–110 mm). Semi-infinite height of burial conditions are attained when any further increase in the height of burial does not influence the impulse transfer to the target plate. The height of burial representing semi-infinite conditions observed in the experiments is a function of the depth of burial. [Copyright &y& Elsevier]

Abstract: High rate delamination tests are often performed using high speed servo-hydraulic or drop-weight test frames. However, impact induced stress wave propagation in the specimen, load cell and test frame often results in oscillations in the force readings which can obscure specimen response. The Hopkinson Pressure Bar provides a means of measuring impact forces and velocities that accounts for stress wave propagation, but is typically used where forces are relatively high and deflections to failure are relatively low. A modified Hopkinson Pressure Bar apparatus was developed to conduct delamination tests, based on Three Point Bend Test geometry, at impact velocities of the order of 5–10m/s, with specimen deflections to failure approaching 10mm. This apparatus was used to test the delamination response of Glass Fibre reinforced Polypropylene specimens, using the mixed Mode I–Mode II Single Leg Bend delamination test. The shape of the force–deflection curve differed dramatically between quasi-static and impact tests. Finite Element Analysis, using cohesive zone elements to capture delamination, was used to elucidate the different response of the quasi-static and impact delamination tests. [Copyright &y& Elsevier]

Abstract: This paper presents experimental and numerical results of an investigation to determine the response of quadrangular steel plates subjected to explosive charges buried under dry construction sand. The buried charges were designed to simulate a landmine blast. Three parameters; depth of burial, stand-off distance and mass of explosive, were varied to provide a range of impulsive loads and plate responses. A vertical ballistic pendulum was used to measure the impulse imparted from the buried charges onto the deformable or rigid target plates. The results showed that as the depth of burial increases the impulse imparted onto the plate increases. The midpoint deflection of the plate reaches a maximum, after which the deflection decreases with a continual increase in depth of burial. The numerical model, developed in ANSYS AUTODYN R12.1a and validated against the experiments, provided insight into the transient response of both the plates and the sand. The numerical models indicated that for most of the tested stand-off distances the sand did not impact the plate as an ejecta but as a sand dome with complete containment of the detonation products. The sand serves to focus the high pressure and high temperature detonation products onto the plate. This focussing effect increases with the depth of burial. The plate deformation is dependent on the amount of energy the sand can absorb (via compaction) which is directly proportional to the depth of burial. [Copyright &y& Elsevier]

Abstract: One-dimensional models for compaction of cellular materials exhibiting strain hardening are proposed for two different impact scenarios. The models reveal the characteristic features of deformation under the condition of decreasing velocity during the impact event. It was established that an unloading plastic wave of strong discontinuity propagates in the foam and it has a significant dynamic effect on the foam compaction and energy absorption. The proposed models are based on the actual experimentally derived stress strain curves. The compaction mechanism in three aluminium based foam materials, two of them with relatively low density – Alporas and Cymat with 9% and 9.3% relative density, respectively and a higher density Cymat foam with 21% relative density, is analysed. Numerical simulations were carried out to verify the proposed models. The predictions of the proposed models are compared with published analytical models of compaction of cellular materials which assume a predefined densification strain. It is shown that the approximation of a cellular material with significant strain hardening by the Rigid Perfectly-Plastic-Locking (RPPL) model can lead to an overestimation of the energy absorption capacity for the observed stroke due to the non-uniform strains along the compacted zone of the actual material in contrast to the predefined constant densification strain in the RPPL model. The assumption of a constant densification strain leads also to an overestimation of the maximum stress, which occurs under impact. [Copyright &y& Elsevier]

Abstract: The experimental results and numerical simulations of “V” shape plates of different included angles (60°, 90°, 120°, 150° and 180° (flat plates)) subjected to localised blast load are presented in this paper. The results of simplified numerical models, carried out using Ansys/AutoDYN, are validated with experiments for deflection. The specimens are made from Domex 700 steel plates folded along the centre to provide different included angles and a constant projected area of 300×300mm. Geometric scaling, based on the size of the Casspir Armoured Personnel Carrier (APC) and TM-57 anti-tank mine, is applied to the “V” shape plates to determine stand-off distance and the size of the explosive (PE4) disc used in the experiments. The range of masses of explosive used includes the scaled mass of a TM-57 anti-tank mine to the same ratio of the ground clearance of the Casspir APC using the Hopkinson–Cranz blast scale law. Different masses of explosive are used to provide results ranging from large inelastic deformation of the plate to tearing. A general trend of increasing permanent mid-point deflection is observed for an increase in charge mass at a constant stand-off distance. While the measured impulse does not significantly change, an increase in mid-point deflection is observed with a decrease in stand-off distance for a constant mass of explosive. The results showed that smaller inclusive angles deflect more blast energy resulting in lower mid-point plate deflection. The predictions show encouraging correlation with experimental data for the displacement profile. [Copyright &y& Elsevier]

Abstract: Sandwich panels constructed from metallic face sheets with the core composed of an energy absorbing material, have shown potential as an effective blast resistant structure. In the present study, air-blast tests are conducted on sandwich panels composed steel face sheets with unbonded aluminium foam (Alporas, Cymat) or hexagonal honeycomb cores. Honeycomb cores with small and large aspect ratios are investigated. For all core materials, tests are conducted using two different face sheet thicknesses. The results show that face sheet thickness has a significant effect on the performance of the panels relative to an equivalent monolithic plate. The Alporas and honeycomb cores are found to give higher relative performance with a thicker face sheet. Under the majority of the loading conditions investigated, the thick core honeycomb panels show the greatest increase in blast resistance of the core materials. The Cymat core panels do not show any significant increase in performance over monolithic plates. [Copyright &y& Elsevier]

Abstract: The response of Fibre–Metal Laminates (FML) to localised blast loading is studied numerically in order to interpret the deformation mechanism due to highly localised pressure pulses causing permanent deformations and damage observed experimentally in FML panels comprising different numbers of aluminium alloy layers and different thickness blocks of GFPP material [Langdon GS, Lemanski SL, Nurick GN, Simmons MS, Cantwell WJ, Schleyer GK. Behaviour of fibre–metal laminates subjected to localised blast loading: part I – experimental observations and failure analysis. International Journal of Impact Engineering 2007;34:1202–22; Lemanski SL, Nurick GN, Langdon GS, Simmons MS, Cantwell WJ, Schleyer GK. Behaviour of fibre–metal laminates subjected to localised blast loading: part II – quantitative analysis. International Journal of Impact Engineering 2007;34:1223–45; Langdon GS, Nuric GN, Lemanski SL, Simmons MS, Cantwell WJ, Schleyer GK. Failure characterisation of blast-loaded fibre–metal laminate panels based on aluminium and glass-fibre reinforced polypropylene. Composite Science and Technology 2007;67:1385–405]. The influence of the loading and material parameters on the final deformation characteristics is examined. Particular attention is paid to the transient deformation process by using finite element and analytical models to analyse the panel behaviour. It is shown that the response of the FML panels is extremely sensitive to the spatial and temporal distribution variation of the pressure caused by the blast loading. The study reveals that the properties of GFPP in the through-thickness direction play an essential role in the velocity transfer, which influences considerably the failure and final deformed shape of the FML panel. Good agreement between the experimental and numerical results is observed. Comparisons between the responses of relatively thin FML panels, monolithic aluminium alloy plates of equivalent mass and a foam-core panel to localised blast are also presented and discussed. [Copyright &y& Elsevier]

Abstract: The mechanism of air blast attenuation in a sacrificial cladding comprising a steel cover plate and a foam core is examined applying an analytical and numerical analysis. For the range of the analysed pressure pulses, the maximum magnitudes of the induced compaction velocities were usually smaller than the acoustic wave speed in the foam material and caused a non-uniform foam density distribution along the compacted region. A significant density decay measured from the proximal end of the cladding was observed within the compacted foam zone due to a rapid reduction of the compaction velocity. An analytical model was developed to reveal the characteristic features of the foam compaction under a moderate velocity impact. It was shown that waves of strong discontinuity, such as shock waves resulting from an overtaking of the stress increments cannot be initiated in the foam. It was revealed, however, that the stress wave propagation in the form of an unloading plastic wave has a significant dynamic effect on the foam compaction and energy absorption. It was concluded that a quasi-static approach cannot be used to accurately estimate the absorbed energy, at least for partially compacted foam. The predictions of the proposed analytical model are compared with other published analytical models for a foam compaction under a high and low velocity impact and with the results from the numerical simulations of the foam deformation in a finite thickness sacrificial cladding subjected to a blast loading. The numerical model was verified with blast loading tests of 50mm thick Cymat foam claddings having a density of 253kg/m3. The influence of the cladding characteristics on the reflected stress from the stationary end of the cladding was also analysed when using the proposed model for foam compaction. [Copyright &y& Elsevier]

Abstract: This paper reports on an investigation into the behaviour of circular sandwich panels with aluminium honeycomb cores subjected to air blast loading. Explosive tests were performed on sandwich panels consisting of mild steel face plates and aluminium honeycomb cores. The loading was generated by detonating plastic explosives at a pre-determined stand-off distance. Core height and face plate thickness were varied and the results are compared with previous experiments. It was observed that the panels exhibited permanent face plate deflection and tearing, and the honeycomb core exhibited crushing and densification. It was found that increasing the core thickness delayed the onset of core densification and decreased back plate deflection. Increasing the plate thickness was also found to decrease back plate deflection, although the panels then had a substantially higher overall mass. [Copyright &y& Elsevier]

Abstract: This paper presents the numerical simulations of thin-walled square hollow steel beams subjected to a uniform transverse blast load. The objectives of the numerical simulations were to gain an insight into the temporal distribution of the global and local deformation and the adiabatic temperature rise in the beams as a result of impulsive loading. Additionally, the finite element predictions using Ls-Dyna are compared to the experimentally observed global and local deformations. The full lengths of the beams were modelled using three material models based on the linear piecewise plasticity material model which incorporated strain hardening, with and without strain-rate hardening and with strain-rate hardening and temperature softening. The blast wave was simulated as a rectangular pressure pulse distributed over the top surface of the beams. Ls-Dyna and the material model used were found to predict the global and local deformation of the beams reasonably well. Incorporating strain-rate hardening was found to be important to be able to predict the global and local deformation of the beams. Thermal softening was found to play a small but not negligible role. [Copyright &y& Elsevier]

Abstract: GLARE© is a fibre-metal laminate that is widely used by the aircraft industry due to its excellent fatigue and impact properties. It has also been proposed as a blast resistant material. This article reports on a set of experiments on GLARE 3, one of the GLARE variants used in impact applications. Results from the preliminary blast tests indicate that the panels behaved similarly to monolithic metal plates and appeared to offer potential for blast resistance when the results are compared to those in the literature for monolithic metal plates. [Copyright &y& Elsevier]

Abstract: This paper presents the results of localised blast tests on fully clamped square fibre–metal laminate panels, manufactured using sheets of 2024-O aluminium alloy, woven glass–fibre reinforced polyamide and a polypropylene adhesive. The fracture properties of the composite–metal interface were determined using the single cantilever beam geometry and the measured interfacial fracture toughness was between values in the literature for thermosetting composites and aluminium/glass fibre polypropylene. Observations from blast experiments performed on panels with different stacking configurations are reported. Diamond and circular back face damage were observed, along with pitting, global displacement and tearing of the front face. Examinations of sectioned panels are presented and multiple debonding, plastic deformation and fibre fracture were identified within the panels. [Copyright &y& Elsevier]

Abstract: The potential error due to friction in compression split Hopkinson pressure bar (SHPB) tests is assessed and conditions for minimising this error are investigated. Theoretical friction factors are inferred from ring compression tests. Experimental results are reported for mild steel, copper and aluminium ring specimens tested quasi-statically (∼10−2 s−1), using a servo-hydraulic test machine, and at high strain rates (∼103 s−1) on a SHPB. Specimens were tested dry, or lubricated using a molybdenum disulphide grease. The influence of surface finish and strain rate on the friction effect is discussed. The inferred friction factors are in the range m=0.08–0.14 (equivalent to Coulomb friction coefficients between μ=0.05 and 0.08). These results imply that the friction error in routine compression SHPB tests of metals lies between 2% and 3%. [Copyright &y& Elsevier]

Abstract: This two-part article examines the behaviour of aluminium alloy–glass fibre-reinforced polypropylene-based fibre–metal laminates (FMLs) subjected to localised explosive blast loading. Part I presents observations from the experiments on samples of varying thickness and material distribution, and investigates the influence of stacking configuration. This extensive study examines panels which have between two and five layers of aluminium, and up to eight plies of composite between each pair of aluminium layers. Diamond and cross-shaped back face damage is observed and varies according to panel thickness. Pitting, global displacement and ring buckling of the front face are also discerned. Some observations are related to wave propagation effects. Part II reports a quantitative analysis of the experimental data. Expressed in terms of non-dimensional parameters, front and back face displacements fall within one plate thickness of a linear trend line. The threshold impulse for the onset of tearing is found to increase linearly with panel thickness. [Copyright &y& Elsevier]

Abstract: This paper investigates the blast response of fibre-metal laminates (FMLs) manufactured from two glass fibre reinforced polypropylene composites and that of a plain aluminium alloy. The FMLs were manufactured by stacking the materials in a mould and applying heat and pressure to them. An autoclave was not used. In this work, attention focuses on elucidating the failure modes in the hybrid laminates. The blast data is non-dimensionalised to develop an empirical formula that characterises the behaviour of these materials under this extreme form of loading. The results indicate that thermoplastic-based FML materials may show potential for use in blast-resistant structures, due to their ability to absorb blast energy through delamination, debonding between the aluminium and composite layers, spalling/petalling of the aluminium, perforation through the layers and bending and stretching of the glass fibres. The tests also highlight the difference in response between panels constructed using woven (symmetrical response) and unidirectional (asymmetric behaviour) GFPP composites. The non-dimensional analysis appears to show that there is correlation between the response of all three panel types. [Copyright &y& Elsevier]

This two-part article presents the results of experimental and numerical work on the response of built-in mild steel quadrangular plates with different stiffener configurations (unstiffened (flat), single (S), double (D), cross (C) and double cross (DC)) subjected to blast loading. Part I reports on the response of these plates to uniform blast loading while localised blast loading is examined in Part II. The approach in both studies is similar—experimental results obtained from blast tests using a ballistic pendulum are presented and compared with finite element simulations. The numerical approach consists of adiabatic analyses of 1/4 symmetry plate model using ABAQUS/Explicit version 5.8. Temperature-dependent material properties, as well as strain-rate sensitivity, are included in the numerical modelling. Large inelastic deformation is well predicted for the various stiffener configurations and size for both maximum deflection and deformation shape. Tearing is predicted by high-temperature bands. [Copyright &y& Elsevier]

A series of experimental results on clamped mild steel quadrangular plates of different thicknesses (1.6, 2.0, 3.0 and 4.0 mm) and varying length-to-width ratios (1.0–2.4) subjected to localised blast loads of varying sizes is reported. Disc shaped explosive charges of varying charge diameter-to-plate width ratios (0.2–0.37) and charge heights (1.8–14 mm) are centrally positioned on quadrangular plates to provide impulses resulting in mid-point deflections in the range from two plate thicknesses to central plate tearing. The effects of varying both the loading conditions and the plate geometries on the deformation are described. A modified dimensionless number is presented for the quadrangular plate response when subjected to localised circular blast loading. In addition, numerical predictions are carried out and compared with experiments for a limited selection of plate geometries. [Copyright &y& Elsevier]

The choice of composite materials as a substitute for metallic materials in technological applications is becoming more pronounced especially due to the great weight savings these materials offer. In many of these practical situations, the structures are prone to high impact loads. Material and structural response vary significantly under impact loading conditions as compared to quasi-static loading. The strain rate sensitivity of both carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) are studied by testing a single laminate configuration, viz. cross-ply [0°/90°] polymer matrix composites (PMC) at strain rates of 10−3 and 450 s−1. The compressive material properties are determined by testing both laminate systems, viz. CFRP and GFRP at low to high strain rates. The laminates were fabricated from 48 layers of cross-ply carbon fibre and glass fibre epoxy. Dynamic test results were compared with static compression test carried out on specimens with the same dimensions. Preliminary compressive stress–strain vs. strain rates data obtained show that the dynamic material strength for GFRP increases with increasing strain rates. The strain to failure for both CFRP and GFRP is seen to decrease with increasing strain rate. [Copyright &y& Elsevier]

The work described herein focuses on the effect a change in the laminate stacking sequence has on the ability to dissipate kinetic projectile energy. Two different T800 carbon fibre filament wound tubes in an epoxy matrix with lay-ups of [−35°/+35°/90°3/−35°/+35°/90°3/−35°/+35°] (laminate A) and [90°6/(−35°/+35°)3] (laminate B) are investigated. The tubes are subjected to impacts up to and above the ballistic limits. The energy dissipated by material failure and friction is quantified and shown to be similar for the two laminates at the respective ballistic limits. The results indicate that laminate B provides the best energy dissipation performance as a result of a higher ballistic limit than laminate A and a difference in the strain energy due to a different local response of the two laminates. [Copyright &y& Elsevier]

• Influence of venting on the blast response of scaled unit load devices. • Internal blasting due to spherical PE4 plastic explosive detonations. • Transient response for unconfined blasted plates. • Confined explosions caused more damage, initiated tearing at plate boundaries. • LS-Dyna showed venting has no effect on the pressure peak, but removed late-time pressure reflections. • Venting from two sides was slightly more effective than single-sided venting. This paper concerns the mitigation of damage in aircraft luggage containers subjected to internal blast loading. It reports findings of experimental and computational work on the influence of venting on the blast response of scaled unit load devices. The internal geometry of the structure was based on a 1:6 scale version of the commonly used LD-3 unit load device. To simplify the problem, only the face closest to the aircraft primary structure could deform whilst the other walls were kept rigid. Small, spherical, charges of PE4 plastic explosive were detonated inside the scaled structures. The fully confined blast tests exhibited the highest permanent displacements and were the only tests to produce rupture of the target plate. Introducing venting reduced the target plate displacement significantly. Computational simulations were developed using LS-Dyna to provide additional insight into the blast loading and its interaction with the structure beyond what could be measured experimentally. Venting appeared to have no effect on the pressure peak, but it was effective at removing the late-time pressure reflections. The influence of the side venting was slightly obscured in the experiments due to boundary pulling-in effects at higher charge masses, but the simulations showed that venting from two sides was slightly more effective in reducing target plate deformation than single-sided venting. The paper demonstrates the potential benefit of using LD-3 ULDs unit load device with canvas sides (rather than solid ones) and venting lengthwise along the aircraft body to redirect the loading away from vulnerable locations. [ABSTRACT FROM AUTHOR]