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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: 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]

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 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: 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]

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 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]

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: 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: 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: 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: 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: The effect of core density and cover plate thickness on the blast response of sacrificial cladding panels has been investigated through blast loading experiments and finite element modelling on structures with steel cover plates and aluminium foam cores. A range of foam core densities were examined, with 10%, 15% and 20% nominal relative densities. The cover plate thickness greatly influenced the response of the sacrificial cladding. Cover plates that were 2mm thick exhibited significant permanent deformations and variable percentage crush across the section, whereas the 4mm thick cover plates were more rigid causing the core to compress uniformly. Considerable fracture of the foam was observed after blast testing, particularly for the lower density foams. The effect of bonding the cover plate to the core was also examined. Numerical simulations of the experiments were performed using ABAQUS/Explicit to provide insight into the response mechanism. It was shown through the finite element simulations that tensile fracture of the foam occurred during the unloading phase of response and that adhesion of the cover plate to the foam caused higher levels of cracking. This was consistent with the experimental observations. [Copyright &y& Elsevier]