Aluminum Foam Core Sandwich Panels Research Articles

High-velocity perforation behaviour of sandwich panels with Al/SiCp composite foam core

Aluminium foam core sandwich panels are good energy absorbers for impact protection applications, such as light-weight structural panels, packing materials and energy absorbing devices. In this study, the high-velocity perforation response of a range of sandwich panels with Al A356/SiCp composite foam core and 1100 aluminium face-sheets has been investigated using a conventional gas gun. Impact perforation tests were carried out using a 10-mm diameter conical nosed indenter at velocities up to that required to achieve complete perforation of the target (i.e. 230 m/s). The effects of face-sheet thickness, density and thickness of aluminium composite foam core on the total, specific and extra absorbed energy and also ballistic limit of the panels during impact penetration were experimentally investigated. During test, top face-sheets globally bended and tore into several pieces and so absorbed part of impact energy. Rupture and densification are two deformation modes and energy absorption mechanisms of foam core. Localized indentation and tearing, global bending and delamination were also observed on back face-sheets. Higher foam core density and thickness and also thicker face-sheets resulted in higher absorbed energy and ballistic limit.

Experimental study on the dynamic responses of foam sandwich panels with different facesheets and core gradients subjected to blast impulse

Sandwich panels with an energy-absorbing core material have exhibited great potential in lightweight structures for blast protection. In this study, the deformation/failure modes of sandwich panels against blast impulse were investigated experimentally. The blast tests were conducted on the aluminum foam-core sandwich panels with different facesheet materials, namely aluminum alloy, steel, and carbon fiber reinforced plastics (CFRP); and the cores involve uniform foam and graded foam. The deformation modes of the whole sandwich panels as well as the front facesheet, foam core, and back facesheet were analyzed systematically. It is shown that the deformation patterns are fairly sensitive to the impulse intensity, facesheet material, and foam core gradient. Based upon the measurements, the back facesheet deflection increases linearly with the impulse, apart from the petal-tearing failure of front facesheet. When considering the specific impulse and the same metallic back facesheets, the blast resistance of the sandwich specimen with CFRP front facesheet is superior to these of the metallic front facesheet specimens. Interestingly, the sandwich panels with the aluminum front and steel back facesheet perform better in blast resistance than those with the steel front and aluminum back facesheet. The blast resistance of sandwich panels with a positive gradient of core density (i.e. core density linearly decreased along the blast direction) is superior to those with a negative gradient of core density; and the performance increases with increasing density difference. Compared with the uniform core, the positively-graded foam core with a larger density difference exhibits a stronger blast resistance, while those with a smaller density difference present a weaker blast resistance. The study is expected to provide some fundamental data and design guide for a more efficient sandwich structure with lighter weight and higher capacity of blast protection.

Experimental and numerical analyses on the dynamic response of aluminum foam core sandwich panels subjected to localized air blast loading

This paper presents experimental and numerical investigations into dynamic responses of aluminum foam core sandwich panels subjected to localized air blast loading. It mainly focused on the effects of face-sheet thickness and mass allocation on the deformation responses and energy absorption characteristics. The specimens considered experienced several deformation/failure modes, including localized deformation of front face, large inelastic deformation of back face, core densification and fragmentation and debonding failure. Experimental results show that both the deformation/failure modes and permanent deformation are more sensitive to the variation of front face thickness relative to the one of back face thickness. The optimal mass allocation strategies for the reduction of deformation response are to distribute more mass to front face rather than back face, and to adopt a thick and suitable strength foam core. Numerical simulations reveal that the increase of front face-sheet thickness led to a remarkable decrease on total energy dissipation while the effect of back face thickness was negligible. The mass allocation strategy with a lighter front face could achieve superior capability in total energy absorption regardless of areal density. Moreover, allocating more mass from back face to foam core is an efficient means to further improve the panel energy absorption.

Experimental study on stress attenuation in aluminum foam core sandwich panels in high-velocity impact

The present work examined the dynamic behaviors of sandwich panels with aluminum foam core and steel faceplates at an impact velocity of about 370m/s. The stress attenuation before and after the foam core during penetration process was measured by means of Polyvinylidene Fluoride transducers. It was found that the stress value was remarkably reduced, and the rise velocity of stress slowed down evidently as foam core was compressed. The profile of the damaged aluminum foam illustrated no obvious localized “X” failure patterns at the velocity tested presently.

Numerical study of energy absorption in aluminum foam sandwich panel structures using drop hammer test

The sandwich structures with aluminum foam core and metal surfaces have widespread use in the absorption of energy, because they are light weighted with high performance in dissipating energy. The cell structure of the foam core is subjected to plastic deformation in the constant compression level that absorbs a lot of kinetic energy before destruction of the structure. In this research, experimental tests of low-velocity impact on the sandwich structure by a drop machine are simulated by LS-DYNA software. Numerical results are obtained for different velocities and weights of projectile on samples of aluminum foam core sandwich panels with relative density (the ratio of the density of aluminum foam to the density of solid aluminum) of 18, 23, and 27. The results are compared with experimental results which reveal a good conformity. As well, from the numerical simulations, the effect of weight, velocity and energy of the projectile and the density of the foam core on the global deformation and energy loss rate of projectile have been studied.

Modelling of aluminium foam core sandwich panels under impact perforation

Aluminium foam core sandwich panels are good energy absorbers for impact protection applications, such as light-weight structural panels, packing materials and energy absorbing devices. In this study, the high-velocity impact perforation of aluminium foam core sandwich structures was analysed. Sandwich panels with 1100 aluminium face-sheets and closed-cell A356 aluminium alloy foam core were modelled by three-dimensional finite element models. The models were validated with experimental tests by comparing numerical and experimental damage modes, output velocity, ballistic limit and absorbed energy. By this model the influence of foam core and face-sheet thicknesses on the behaviour of the sandwich panel under impact perforation was evaluated.

Impact perforation of sandwich panels with aluminum foam core: A numerical and analytical study

This paper tends to study the observed piercing force of sandwich panels with foam cores under impact loading by numerical and analytical methods. For this purpose, numerical models are built using LS-DYNA and calibrated with the inversed perforation test instrumented with an instrumented pressure bar on the AlSi7Mg0.5 Aluminum foam core sandwich panels with 0.8 mm thick 2024T3 Aluminum top and bottom skins. Actually, the proposed numerical model can predict piercing force vs. displacement curves in good agreement with experimental measurements (tests at impact velocities at 27 and 44 m/s). More confidence is obtained by the fact that the simulation can also reproduce the failure mode of the top skin and bottom skin.Virtual tests using this numerical model are conducted with higher impact velocities up 200 m/s. A continuous increase of the piercing force of top skin with impact velocity is found. A careful analysis of numerical results (difference between top and bottom skin perforation, stress level beneath the top skin, etc.) shows that the foam core strength enhancement due to shock front propagation is responsible for this piercing force increase under impact loading.Finally, an analytical model using an improved RPPL shock model based on a power law densification assumption is proposed to calculate the top skin piercing forces. This analytical model provides a prediction in good agreement with the experimental and FE results in a large range of impact velocities.

Perforation of aluminium foam core sandwich panels under impact loading: A numerical and analytical study

This paper reports the numerical results of the inversed perforation test instrumented with Split Hopkinson Pressure Bar SHPB with an instrumented pressure bar on the AlSi7Mg0.5 aluminium foam core sandwich panels with 0.8 mm thick 2024 T3 aluminium top and bottom skin. The numerical models are developed in order to understand the origin of the enhancement of the top skin loads found under impact loading (paper published by [1]). Numerical predicted piercing force vs displacement curves are compared with experimental measurements (tests at impact velocities at 27 and 44 m/s). The simulation catches all process of the perforation of the sandwich panels (top skin, foam core, and bottom skin). Within experimental scatter, there is a good agreement between numerical predictions and experimental measurements. Virtual tests with different impact velocities up 200 m/s are presented and showed a significant enhancement of the piercing force under impact loading (top skin peak and foam core plateau loads). In order to understand the origin of these force enhancements, any difference of detailed local information between static and dynamic loading is studied and showed that a shock front effect is responsible for the enhancement piercing force. An analytical model using an improved RPPL shock model based a power law densification assumption is proposed to calculate the top skin piercing force. The improved RPPL shock model agrees with the FE results for small velocities and gives better prediction of the piercing force than the RPPL shock model for large velocities (>100 m/s).

Projectile impact testing of glass fiber-reinforced composite and layered corrugated aluminium and aluminium foam core sandwich panels: a comparative study

E-glass/polyester composite and layered corrugated aluminium and aluminium foam core sandwich panels were projectile impact tested between 127 m/s and 190 m/s using a hardened steel sphere projectile. The corrugated aluminium cores, constructed from aluminium fin layers and aluminium interlayers and face sheets, exhibited relatively lower-plateau stresses and higher stress oscillations in the plateau region than aluminium foam cores. The applied brazing process resulted in reductions in the plateau stresses of the corrugated aluminium cores. The sandwich panels with 2- and 3-mm-thick composite face sheets and the epoxy-bonded corrugated aluminium sheet cores were perforated, while the sandwich panels with 5-mm-thick composite face sheets were penetrated in the projectile impact tests. On the other hand, the sandwich panels with aluminium foam cores were only penetrated. A simple comparison between the ballistic limits of the sandwich panels as a function of total weight revealed significant increases in the ballistic limits of the cores with the inclusion of composite face sheets. The determined higher impact resistance of the foam core sandwich panels was attributed to the relatively higher strength of the foam cores investigated and the ability to distribute the incident impulse to a relatively large area of the backing composite plate.

Perforation of aluminium foam core sandwich panels under impact loading—An experimental study

This paper reports an original inverse perforation tests on foam core sandwich panels under impact loading. The key point is the use of an instrumented Hopkinson pressure bar as a perforator and at the same time a measuring device. It aims at a high quality piercing force record during the whole perforation process, which is a weak point of common free-flying projectile-target testing schemes. This new testing arrangement allows for the measurement of piercing force–displacement curves under quasi-static and impact loadings of sandwich samples, which is made of 40 mm AlSi 7Mg 0.5 Cymat foam cores and 0.8 mm thick 2024 T3 aluminium sheets as top and bottom skins (incident and distal side facesheets). Compared with quasi-static top skin peak loads (the maximal load before the perforation of top skins) obtained under same geometric and clamping conditions, a significant enhancement under impact loading (25%) of the top skin peak load is found. However, the used foam core and skin sheet are known and have been confirmed to be hardly rate sensitive by separate tests on foam cores as well as on the skin sheets. A possible explanation of these puzzling results is following: the foam core under the perforator was locally more compressed under impact loading because of the inertia effect. As the used foam cores has a quite important strain hardening behaviour, the strength of foam cores before the failure of the top skin is higher than that under quasi-static loading, which leads to an increase of the top skin peak load under impact loading. Tests on a uniformly pre-compressed sandwich sample exhibit indeed higher top skin peak loads, which supports also this aforementioned concept.

Perforation of aluminium foam core sandwich panels under impact loading

This paper reports an original inverse perforation tests on foam core sandwich panels under impact loading. The key point is the use of an instrumented Hopkinson pressure bar as a perforator and at the same time a measuring device. It aims at a high quality piercing force record during the whole perforation process, which is a lack of common free-flying projectile - target testing schemes. This new testing arrangement allows for the measurement of piercing force-displacement curves under quasi-static and impact loadings of sandwich samples, which is made of 40 mm AlSi7Mg0.5 Cymat foam cores and 0.8 mm thick 2024 T3 aluminium sheet as top and bottom skins. Compared with quasi-static top skin peak loads (the maximal load before the perforation of top skins) obtained under same geometric and clamping conditions and even in the case that the used foam core (Cymat) and aluminium skin sheet are known and have been confirmed rate insensitive, a significant enhancement under impact loading (25%) of the top skin peak load is found.