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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: 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 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: 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]

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 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]

The study detailed in this manuscript focuses on the numerical and experimental testing of circular AA6061-T6 aluminum alloy extrusions subjected to cutting deformation modes under blast loading conditions, as energy dissipation devices. The experimental investigation was completed utilizing a specially designed cutter with the presence of a deflector mounted on a ballistic pendulum. Plastic explosives (PE4) where charge masses varied from 20 g to 40 g were used to initiate blast loads. Experimental results revealed that the cutting deformation mode was repeatable and controllable having a stable and clean curling cut. Numerical simulations of the detonation as well as the axial cutting deformation process employing an Eulerian finite element formulation were performed. Numerical detonation models were in good agreement with experimental results having an average standard error less than 3% for impulse predictions. Good predictive capabilities of the numerical model for the axial cutting behaviour and large scale deformation response were observed. An almost constant force during cutting was observed, which eliminated the initial high peak crush force associated with a dynamic plastic collapse deformation mode. The average mean cutting force, measured at the load cell for both experimental and numerical testing methods as a result of cutting deformation was observed to be 33.5 kN for the specific specimen geometry and material. Finally, a force analysis was conducted using theoretical and numerical models to study the steady-state cutting condition. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the influence of varying core density on the blast resistance of sandwich panels based on crosslinked PVC cores and aluminium alloy skins. Initially, the findings of a series of compression and single edge notch bend and shear tests are presented in order to characterise the strength and toughness characteristics of the foams and generate data for input into the finite element models. Experimental blast tests employing a ballistic pendulum are then reported, where it is shown that damage within the sandwich panels becomes more severe as the density of the foam core is increased. Indeed, panels based on the lowest density foam (60 kg/m3) did not exhibit any fracture or debonding over the range of impulses considered, instead absorbing energy through plastic deformation in the metal skins and compression of the foam core. In contrast, significant damage, in the form of Mode I core cracking and debonding at the skin–core interface, was apparent in the higher density core systems. A finite element analysis has been employed to model the blast response of the sandwich structures. The FE models successfully predicted the post-test deformed shapes of the panels. These analyses were also used to determine the individual contributions of the skin and core to the energy-absorbing capacity of the various sandwich structures. Here, it was shown that the foam core absorbs more than fifty percent of the overall energy dissipated during the test. [Copyright &y& Elsevier]